Digging in the Sandbox

  • Here’s a quick demo of the new material tool, showing how the tool is used, and how the different materials affect both visuals and physics.

  • ScriptableObjects For Fun and Profit

    Well, it’s been a while, so time for a progress update I think!  The material tool is now done, and I’ll show it in action very soon, so watch out for that.  Most of my time however has been occupied with a massive code re-architecture effort, and that’s what I’m going to go over in this update.

    From a high level perspective the GearBlocks game code is quite well laid out in terms of separating various subsystems (e.g audio, graphics, player, UI, etc.) via namespaces and so on.  However, there was still a lot of code coupling (i.e. direct dependencies) between areas of the game code that should really be completely independent.  This made it impossible to reuse or test parts of the code independently, and it was only going to get worse as development progressed.

    ScriptableObjects to the Rescue

    I’d been using ScriptableObjects in Unity for a long time, but only in a select few cases as data containers, I certainly hadn’t been using them to their full potential.

    I watched these two excellent presentations a while back:-

    Ever since, I’d been wanting to adapt the ideas presented in these talks to the game to improve the code architecture, and so I finally decided to take the plunge.  This was a huge endeavour, but well worth it I think.

    ScriptableObject Events

    Previously I was using Unity’s ExecuteEvents system as the basis for events in the game.  This was helpful for code decoupling, however it still had some disadvantages:-

    • In order to add a new event, a new interface has to be written (derived from IEventSystemHandler), and then implemented in all the MonoBehaviours that need to receive the event.
    • It’s necessary to explicitly call ExecuteEvents.Execute() on every GameObject with MonoBehaviours that need to receive the event.  To me, this makes ExecuteEvents more like messages than true events, but perhaps that’s just semantics.
    • Only MonoBehaviours on GameObjects can receive these events, ScriptableObjects can not.

    So I replaced these with a new system, where each event is now a ScriptableObject asset.  Here’s a simplified version of the code:-

    public class EventAsset : ScriptableObject
       public delegate void EventHandler();
       public event EventHandler Handler = null;

        public void Raise()
           if( Handler != null )

    The real implementation is slightly more complex, but follows the same principle.  It’s implemented using C# generics to allow for different event argument types, and has support for logging and listing the current event subscribers.  This is used by a custom editor I wrote to display this info while the game is running in the Unity editor, here’s an example of it in action:-

    To use an event it can simply be assigned to a variable in the Unity inspector, then to receive it, just subscribe to Handler:-

    public class Receiver : MonoBehaviour
    [SerializeField] EventAsset somethingHappened;

    EventAsset.EventHandler onSomethingHappened;

    void OnEnable()
    onSomethingHappened = () => { Debug.Log( "I hear that something happened!" ); };
    somethingHappened.Handler += onSomethingHappened;

    void OnDisable()
    somethingHappened.Handler -= onSomethingHappened;

    Or to raise the event, just call Raise() on the event:-

    public class Sender : MonoBehaviour
       [SerializeField] EventAsset somethingHappened;

        void SomethingHappened()
           Debug.Log( "Something happened, telling everyone!" );

    This setup has some useful advantages over the old ExecuteEvents system:-

    • No need to write any code to add a new event, just create a new event asset and assigned it in the inspector where needed.
    • No need to explicitly refer to specific GameObjects to send the event.
    • Don’t even need to be using GameObjects, these events can be used by ScriptableObjects as well as MonoBehaviours.
    • The events are more easily debuggable via the custom editor.

    ScriptableObject Variables

    Events aren’t always the most appropriate pattern for sharing data between subsystems, for example sometimes it’s necessary to store a value somewhere and allow it to be read a later point, perhaps continuously polling it to watch as it changes.

    Previously I was doing this by having my subsystems be singletons, and then directly reading / writing properties in them where needed, thereby tightly coupling different areas of the code together, not good!  To solve this I made a new “variable” system, where each variable is a ScriptableObject asset.  Whereas events can be thought of as radio broadcasts, the variable system is conceptually more like a noticeboard (with each variable being a notice pinned to the board).

    Here’s a simplified version of the code, it’s implemented as a generic class to allow for different variable types:-

    public abstract class VariableAssetBase<T> : ScriptableObject
       [SerializeField] T value;

        public T Value { set { this.value = value; } }

        public static implicit operator T( VariableAssetBase<T> variableAsset )
           return variableAsset.value;

    For example, a bool variable type:-

    public class BoolVariableAsset : VariableAssetBase<bool>

    Again, the real code has a bit more going on.  It has an event delegate that code can subscribe to, in order to be notified when the variable value is assigned to (this saves having to use a separate event for this).  It also has support for serialisation so that I can use these variables for things like game settings (e.g. controls, gameplay, video) and allow the player to save / load them.  Plus I made a custom editor that allows variable values to be viewed or even modified while the game is running in the Unity editor.  At some point I might implement a debug console that would allow this to be done even in standalone builds, which would be super cool!

    To use a variable it can be assigned in the inspector, then written to / read from.  Notice that Assigner and Watcher in this example are completely independent of one another:-

    public class Assigner : MonoBehaviour
       [SerializeField] BoolVariableAsset isThingTrueVar;

        void ThingBecomesTrue()
           isThingTrueVar.Value = true;

    public class Watcher : MonoBehaviour
       [SerializeField] BoolVariableAsset isThingTrueVar;

        void Update()

       void PollThingTruthiness()
           Debug.Log( "Thing is currently " + isThingTrueVar );

    I replaced data in my subsystems that needed to be shared with these new ScriptableObject variables.  This allowed me to remove a lot of code dependencies, and eliminate the need for singleton references in most cases.

    One example being the UI overlay that displays the player’s speed, acceleration, and altitude.  It now just reads variables for these values and displays them, completely independently of the player code that updates them.

    ScriptableObject Dictionaries

    There’s one slight wrinkle with the ScriptableObject variable system, in that there is only one global instance of each variable.  For example, sometimes I need one instance of a variable per player (in multi-player games).  To solve this I implemented a simple ScriptableObject dictionary, here’s the implementation pretty much in full:-

    public abstract class DictionaryAssetBase<TKey, TValue> : ScriptableObject
       Dictionary<TKey, TValue> dictionary = null;

        void OnDisable()
           if( dictionary != null )

        public TValue this[TKey key]
               if( dictionary != null )
                   TValue value;
                   if( dictionary.TryGetValue( key, out value ) )
                       return value;

                return default(TValue);

               if( dictionary == null )
                   dictionary = new Dictionary<TKey, TValue>();

                dictionary[key] = value;

    Then for example, a dictionary with byte keys and bool values:-

    public class ByteBoolDictionaryAsset : DictionaryAssetBase<byte, bool>

    The only part I left out here is some code for listing the entries currently in the dictionary, used by another custom editor I added for debugging while the game is running in the Unity editor.

    A dictionary is used in much the same way as a ScriptableObject variable:-

    public class Assigner : MonoBehaviour
       [SerializeField] byte thisPlayersID;
       [SerializeField] ByteBoolDictionaryAsset isThingAboutPlayerTrueVar;

        void PlayerThingBecomesTrue()
           isThingAboutPlayerTrueVar[thisPlayersID] = true;

    public class Watcher : MonoBehaviour
       [SerializeField] byte thisPlayersID;
       [SerializeField] ByteBoolDictionaryAsset isThingAboutPlayerTrueVar;

        void Update()

        void PollPlayerThingTruthiness()
           Debug.Log( "Thing is currently " + isThingAboutPlayerTrueVar[thisPlayersID] + ", about player with ID: " + thisPlayersID );

    Replacing Singletons

    The game has many self contained code modules providing utilities and functionality used by other parts of the code.  Previously these were either static classes or singleton MonoBehaviours, both having their disadvantages:-

    • Static classes can’t have variables serialized by Unity or edited in the inspector.
    • Singleton MonoBehaviours need to live on a GameObject somewhere in the scene (or at least in a prefab).

    So now I’ve re-implemented most of these as ScriptableObjects which have neither of these downsides.  They work well with the new ScriptableObject events too, these modules being able subscribe to or raise events, which helps with code decoupling.

    Other Uses of ScriptableObjects

    I found many more places to use ScriptableObjects, far too many to go over in detail now, but here’s a brief summary of a few of them:-

    • Added ScriptableObject “delegate objects”, making use of the strategy pattern where different variations on a theme implement a common interface.  For example I use this for the procedural generation code for the various different re-sizable parts in the game.
    • Replaced some enums with ScriptableObject assets.
    • Implemented ScriptableObject data assets with built in functionality for better separation of concerns.  For example, I implemented a “sound asset” ScriptableObject that handles random AudioClip selection and playback, and then created a whole bunch of these assets for all the sounds in the game.

  • New material tool, and a new year!

    Hey all, hope everyone has had a good holiday break.  I thought I’d give a quick update on what I’ve been working on over the past few weeks.

    Toolbox code refactoring

    Up until now, the code for the various tools (builder, linker, painter, etc.) was pretty much all in one (very large) source file.  This was driving me crazy as made it a real pain to to fix bugs, or add new features.  So I finally took some time to do something I’d been wanting to do for ages, which was to refactor this monolithic beast into separate source files for each tool.

    There are still things I’d like to improve and clean up (further code decoupling, mainly), but it’s much better than it was, and makes it easier to add new tools, on which subject…

    Material swapper tool

    After the refactoring, I started work on a new tool that allows you to swap the material on certain parts (such as beams and plates) after they’ve been spawned, and even after they’re already part of a construction.

    The first step was to add a material definition that encapsulates all the various part material properties (i.e. the rendering & physics materials, density, strength, and “is it paintable”).  Next I had to refactor the part descriptor code to allow parts to use this new material definition (seems like I’ve been doing a lot of code refactoring lately!)


    Then on to the material tool itself, which I’m still in the middle of building.  Right now I have a first pass implementation working, with the basic UI done, and the ability to change material on the highlighted part.  There’s still more to do however; for example, save / load (including converting old save files to the new material swappable parts), and probably more refactoring as I’m not quite happy with how the part descriptor code is structured just yet.

    Anyway, it shouldn’t take too much longer to finish up, once it’s done I’ll reveal more about how it works.  After that I’ll probably get back to finishing up the linker tool, as that’s been on the back burner for way too long now.

    In the meantime, I’d like to say a big thank you for following my progress, particularly to those of you that have been following for a long time, and who continue to play the demo and give me feedback.  I know development of the game is frustratingly slow, but I will get it done eventually, I hope!

    Happy New Year, and all the best for 2019.

  • Damage is done

    Well, it took me long enough, but finally the damage system is complete!  Most of the time was actually spent doing optimisation work, which I’ve discussed before in previous posts, the damage system itself didn’t take that long to do.

    On the idea scrapheap

    My original idea for damage was that each attachment between parts (fixed, rotary, linear, etc.) would have a “health” value.  Then upon a collision contact with a part, some damage amount would be propagated out to all of that part’s attachments.  For each attachment, damage would effectively accumulate over time as its health value gradually reduced, until it reached zero at which point the attachment would be deleted.

    However, there were problems with this method:-

    • Deleting individual attachments due to damage would lead to inter-penetration issues, just like when you manually delete attachments with the builder tool.
    • Each attachment having a health value would need to be conveyed somehow to the player via a UI, and I couldn’t think of a way which wouldn’t be messy and confusing.
    • Because damage is applied for every collision contact (of which there can be many), the code is quite performance sensitive, and so needs to be as lightweight and simple as possible, which this method wasn’t.

    Binary break

    So in the end I went with a simpler solution that just uses a “strength” threshold.  When a part receives a collision contact, I simply compare the impact force with the part’s strength value, and if the force is greater than this value, I break the part off (i.e. delete all of its attachments), otherwise I leave it attached.  In other words, a part is either entirely broken off or it isn’t, there’s no intermediate damage state or health values to deal with.

    Happily, I found was that there was not really any need to explicitly propagate the damage force to neighbouring parts to achieve a convincing effect.  Direct impacts seem to be enough, I think because as parts break off they hit other parts and the damage sort of propagates organically.

    I’ve also finished the implementation of explosives that integrates with the same damage system, in this case the damage force is simply derived from a linear fall off from the explosion centre.  The resultant bits that are broken off then have an explosion force applied to them to push them around, seems to work pretty well.

    Lastly, I’ve also added a per-construction setting to enable / disable invulnerability (i.e. immunity from part breakage), as sometimes it could be useful to disable damage for those particularly “experimental” constructions that might try and smash themselves to bits.

    Still to do

    As I mentioned, each part has a strength value which basically determines how hard it is to break off.  A part’s strength value is intended to reflect the material it’s made from (e.g. steel is stronger than wood or plastic), and I still need to fine tune these strength values to get the balance correct and hopefully give a nice trade off between the various materials.

    Also, I’m thinking I might bias each part’s strength value slightly based on the number of attachments it has, so that the more other parts it’s attached to, the harder it is to break off.  Again, hopefully giving the player further interesting trade offs to choose between when building their constructions.

  • Yet more optimisations

    OK, it seems I spoke too soon when I said in the last blog post that I was done with optimisations to the construction modification code!  When working on the damage system, I found that detaching parts off large constructions with lots of parts could still be really slow, so over the last few weeks I’ve been working to resolve this.

    Setting transform parents

    When modifying a construction (i.e. attaching or detaching parts), I need to change transform parents in order to manipulate the construction’s transform hierarchy, and by far the biggest performance cost I found was with this re-parenting.  Even when setting worldPositionStays to false when calling SetParent() so that Unity doesn’t have to recalculate world transforms, it’s still really slow when you call SetParent() a lot, due to Unity internally updating the physics colliders.  When modifying a large construction, in the profiler I was seeing Physics.HandleColliderHierarchyChanges and Physics.SyncColliderTransform costing many tens, sometimes hundreds of ms!

    So now I’ve done everything I can to get rid of unnecessary re-parenting, thereby minimising the number of SetParent() calls, specifically:-

    • When fixedly attaching parts together, all the parts have to be re-parented from their current rigidbodies to a single rigidbody.  Now, parts from the rigidbody with the smaller number of parts always get re-parented to the rigidbody with the larger number (without re-parenting the larger number of parts).
    • Similarly, when deleting fixed attachments, parts need to be re-parented to separate rigidbodies.  Now, after determining the groupings of parts left after attachment deletion, the largest group always stays under their original rigidbody, and the rest get re-parented to other new rigidbodies.
    • Lastly; I was parenting rigidbodies that were part of the same construction to a container gameobject, this was handy for clarity and debugging purposes, but not strictly necessary.  I changed the code to maintain the rigidbody-to-parent-construction relationship a different way, rather than relying on the transform hierarchy for this.  After that I was able to eliminate setting of the rigidbodies transform parents entirely.

    Other optimisations

    I was using List<T> to hold temporary lists of parts and rigidbodies when determining how to reorganise a construction hierarchy after deleting attachments.  If there were a large number of things in these lists (e.g. parts), then calling Contains() or Remove() on them would be noticeably slow because these are O(n) operations (a linear search).  So I switched over to using a HashSet<T> instead, for which these operations are O(1).

    After a construction is modified, its rigidbodies bounds and mass properties (e.g. centre of mass, inertia tensor, etc.) need to be recalculated.  I’ve now optimised the code that does this, mostly by caching data that doesn’t change (e.g. for parts that haven’t been re-parented to a new rigidbody).

    Also after a construction is modified, a few GetComponentsInChildren() calls were being used to cache references to rigidbodies and parts.  These calls were quite slow (and also caused some pretty sizable GC allocs), but after restructuring the code a bit, I was able to eliminate the need for them.


    All of these optimisations added together have made huge gains, at least in the test case I was using (a construction with over 2000 parts).  It used to be that detaching a single part in this test could take well over 300ms(!) which caused a noticeable frame rate hitch, now it takes less than 37ms.

    Around 22ms of this remaining time is taken by updating rigidbody mass properties (assigning to mass, centerOfMass, inertiaTensor, and intertiaTensorRotation), which there’s not much I can do about.  I can’t understand why this would be so slow, something odd seems to be happening under the hood in Unity.  Maybe this issue is fixed in Unity 2018, but for now I’m stuck on 2017.4, due to the Networking API issues I’ve discussed in previous posts.  Another 12ms out of the ~37ms total is taken by Unity in Physics.UpdateBodies, which I don’t think I can do anything about either unfortunately.

  • Networking and optimisations

    Sorry for the lack of updates for the past couple of months, I was away visiting family and things for some of that time, but I have also made a lot of progress on the game.  So let’s dive in!

    Networking layer

    Most of my time lately has been spent on networking code.  As I discussed in the previous post, the Unity networking API situation at the moment is unfortunate to put it mildly.  To mitigate against this, I’ve now built a new networking abstraction layer.  This wraps and hides away all direct access to the deprecated Unity RakNet based API that I’m currently using, and should facilitate easier migration to a different networking API in the future.

    This was a big task as it touched code throughout the game.  There are four major aspects to the networking API that needed to be eliminated from the game code: Network static API, network messages, NetworkView, and NetworkPlayer.  In more detail:-

    1. Network static API, e.g. Network.isServer, Network.SetSendingEnabled(), etc.  These are now only used inside the networking layer (or where absolutely necessary, wrapped behind a new API for use in game code).
    2. Network messages, e.g. OnServerInitialized(), OnPlayerConnected(), etc.  These are now only used inside the networking layer, and where necessary propagated out to the game code via events.
    3. NetworkView, used for remote procedure calls (RPCs) and state serialization:-
      1. RPCs.  The new layer now allows game code to register methods, then remotely call, and receive them.  Internally this currently is still implemented using a NetworkView and RPCs.
      2. State serialization via OnSerializeNetworkView() and BitStream.  I’ve now implemented a system within the networking layer to synchronize state across the network.  Internally this is still implemented using a NetworkView, OnSerializeNetworkView(), and BitStream, but none of this is exposed to the game code.
    4. NetworkPlayer, used to uniquely identify a connected player.  Now the new networking layer assigns its own ID for each player, and keeps a reference to each player’s NetworkPlayer for use internally only

    After of all of these changes, the Unity networking API is no longer directly referenced anywhere in game code.  The next step will be to actually change the networking layer’s internal implementation from using the Unity API to something else.  This will likely still be a painful task, but should be far more manageable now than it would have been before.

    Construction modification optimisations

    In the previous blog post I talked about the optimisations I’d done to the construction modification code (this code deals with attaching and detaching parts).  The performance of this code is particularly important in the context of the damage system which can require a large number of parts to be detached at once.

    I have now implemented a GameObject pooling system, which eliminates the last major remaining performance cost, that being the instantiation and destruction of construction and Rigidbody GameObjects.  In the example I showed in the last post (shown again below), the cost of breaking the attachments is now down to less than 10ms (prior to doing any optimisations, it was around 60ms!)


    There are still more optimisations I can do.  For example, the instantiation and destruction of the attachments between parts are contributing some performance cost (and GC allocs).  Plus, associated with the attachments are the physics ConfigurableJoints between Rigidbodies, which also have to be created and destroyed.  Maybe I could pool these too, something to look at in the future for sure.

    But for right now I’m happy enough with the performance that I can get back to working on the damage system.

    Damage system

    On which subject, I’ll be returning my focus to this next.  I still need to decide how to propagate collision forces to cause plausible breakage of parts.  Also, I’m leaning away from the idea of damage accumulation and attachment “health”, towards more of a probabilistic method, but I’m not entirely sure yet.

  • Optimisations and explosions

    As I’ve alluded to in previous updates, the damage system is still a way off from completion, so that’s what I’ve been working towards over the last month or so.  One challenge is to design a system to propagate and accumulate damage in a way that is, if not realistic, at least plausible, as well as making sense to the player (without being frustrating or annoying).

    Before I can get to this though, there is a more fundamental problem.  Breaking parts off a construction due to damage requires efficient construction modification code, and the existing system just isn’t fast enough.

    UI Optimisations

    The first problem I looked at was with the construction list in the world tool UI.  Whenever a construction is created or destroyed, this list in the world tool UI gets updated accordingly.  When a part gets broken off a construction, it’s re-parented under its own new construction GameObject, and this process was getting slowed down by the world tool UI being updated.

    So now the UI elements in this construction list are held in a pre-allocated pool and used / reused as needed, which avoids the performance cost and GC alloc of instantiation when a new entry is added.  Also, the UI update code now queues up any new constructions and only adds one element to the UI per frame, this results in a slight visible delay as the player sees the UI updating itself, but avoids a single frame performance spike.  In fact I made these changes to all other UI screens too that have a large list of entries (for example, the saved game screens).

    Construction modification code optimisations

    I’ve now also optimised the construction modification code (actually I had to completely restructure it) to be simpler and more efficient.  It now uses fewer server-to-client RPC calls, only one per player operation (operations being things like attaching a part, deleting an attachment, etc.)  There are less GC allocs too, as it now reuses many of the temporary data buffers these operations require.

    These changes so far have made a big difference.  I hacked in a key so I can trigger the deletion of all attachments in a construction for testing purposes, as you can see in the example below.  In this example the cost of breaking the attachments went from around 60ms to less than 25ms on my machine, still a significant performance spike, but definitely moving in the right direction.


    The major remaining performance cost is with instantiating new construction GameObjects, and also the Rigidbody GameObjects that live under them (as I mentioned before, parts get re-parented to these when they’re broken off an existing construction).  So, just like with the UI elements, to solve this I’m going to need pre-allocated pools of these GameObjects.  However before I do this, to make life simpler, I need to remove all references to Unity networking stuff from the constructions.  Which brings me to another issue…

    Unity networking API woes

    GearBlocks is still using the old RakNet based Unity networking API, which has been deprecated for a while (and now completely removed from Unity 2018.2).  I was waiting for Unity’s replacement for it - UNET, to be a bit more mature before I switched to it, but sadly UNET has now also been deprecated.  Apparently there’s another replacement solution coming at some point in the future.  Anyway, I guess it’s a good thing I never switched to UNET, it will be supported for another couple of years I believe, but there doesn’t seem much point using it now.  So the upshot is, I’m probably going to have to look for a third party solution.

    Whatever networking solution I end up using, one thing is for sure, I really need to abstract the networking API away from the rest of the GearBlocks code as much possible.  This is something I should have done in the first place really, it’ll make changing networking APIs much easier in the future.

    So to allow for pooled construction GameObjects, and as a first step towards this abstraction, I’ve now implemented my own world object ID system.  This allows GameObjects to have a unique ID consistent across the server and all the clients, and is now used by construction and part GameObjects.  This allowed me to remove the Unity NetworkView from the construction GameObject (which will make pooling them easier), and move all code for state synchronisation out of the construction and into a central manager that synchronises the state of all constructions together.

    The next step in this abstraction effort will be to wrap all the RPC calls (currently scattered throughout the code) behind another interface.  As well as meaning there will then only be one place in the code to modify when I change networking APIs, it will also allow me to remove the NetworkView from part GameObjects too.

    Explosives go boom

    My future plans for GearBlocks mean that the damage system needs to apply damage not only from collision impacts, but also from explosives.  So I had some fun adding a simple placeholder explosive that’ll serve as a good test for now.  Right now it only applies a force to nearby objects, it doesn’t do any damage yet, that’s something I’ll have to work on soon!


  • Here’s a quick update on some of the changes in the new demo build: world tool UI improvements, preventing part inter-penetrations, better collision sounds, and more.

  • GearBlocks Demo 0.5.6773

    I had to fix a few last minute issues as is usually the way, but finally here’s the new demo release as promised.  Enjoy!

  • Glitch fixes, demo update soon

    Last week I fixed a problem that someone found while playing the demo, player feedback is so valuable and always much appreciated by the way!  Here’s the scenario; the player deletes a jointed attachment (e.g. rotary, slider, etc.) between two intersecting parts, but the parts still belong to the same construction after the deletion.  Physics will consider these parts to be inter-penetrating, and if the construction is unfrozen, it’ll try to force them apart.  This can sometimes cause your constructions to jump all over the place like they’re possessed.  Here’s an example of the problem.


    The solution I came up with was to keep track of the intersections left after attachment deletion, and prevent the construction from being unfrozen until they are resolved.  The player can do this by deleting other attachments until the intersecting parts are no longer part of the same construction.  Any unresolved intersections are now shown by a red cross as can be seen below.


    I’ve also been working on a bunch of bug fixes, mostly regressing issues introduced by recent changes.  Another more serious problem was a crash that sometimes happened when quitting the game, the Unity error log didn’t point to anything obvious in my script code, and I couldn’t find any other devs on the forums having a similar issue.  After a lot of trial and error I found which version of Unity introduced the problem.  So I rolled back to 2017.4.2 for now, any 2017 version after this seems to have the crash (I haven’t tried any 2018 releases yet).  I don’t know what was changed that caused this crash, I didn’t find any clues in the Unity change logs.  After the next demo release, I’ll just upgrade to the latest 2018 build and with any luck the issue won’t reappear.

    Speaking of the demo, I should be ready to put the next update out in a day or two.  I finally got my new video card today to replace the one the died, so I’m now able to do some final testing before the release.

  • Collision exposition

    As I mentioned in the last dev update, I’ve been working on re-implementing the collision contact system, which is used for triggering impact sounds and applying damage to constructions.  I’ve now finally completed this work, not without some challenges along the way though, and it ended up taking far longer than I was hoping.  Not to mention my video card died and my Internet connection went down last week, fun times!

    Apologies for the wall of text, but here’s my attempt to explain what I’ve been up to.

    Impact overload

    The old collision code dated from the early prototype days, and simply played an impact sound (and applied damage to the construction) directly in the OnCollisionEnter() event handler.  This event gets triggered once for every collider pair that makes contact, which can end up being a lot particularly if there are many moving parts in a construction, and meant that way too many impact sounds were being triggered concurrently.

    Also, I’ve been working on adding sliding sounds for when parts slide past one another.  This requires continuously tracking collision contacts, for which I use the OnCollisionStay() event.  Again, this event gets triggered once for every contacting collider pair, except that unlike OnCollisionEnter(), it gets called every fixed update for the duration that the colliders are contacting one another, so the performance cost of any code in the event handler becomes a real concern.

    Unity performance woes

    On the subject of performance, the overhead for Unity to collect the collision contact data is one thing, but what I find even more frustrating is the way it must be accessed.  For every single collision contact, a call from the Unity engine (unmanaged C++ code) into the C# script is made via an OnCollision…() event, with an attendant GC alloc for the collision data being passed into the event handler.  This means in my “worst case” tests where I had thousands of collision contacts per update, I was seeing a performance cost in the tens of milliseconds, and thousands of GC allocs totaling a few MB.  This cost is just for reporting the collision contacts, and does not include the physics sim update or anything else.

    I wish it were possible to access all of the per update collision contact data in one call, preferably into a pre-allocated buffer, but for now we’re stuck with the OnCollision…() events.  Hopefully at some point Unity will improve this situation!

    I tried to find a way of eliminating OnCollisionStay() while still keeping the sliding sounds working.  It seemed like it should have been possible because you can still keep track of what colliders are currently contacting by using OnCollisionEnter() / OnCollisionExit(), and then get the velocities from their rigidbodies.  Unfortunately what you don’t have is the new contact position and normal each update, which are required to calculate the relative velocity at the point of contact, necessary for the sliding sounds to work properly.  I tried fudging my way around this by estimating these values, but couldn’t come up with a solution that worked reliably.

    In the end I resigned myself to keep using OnCollisionStay(), and turned my attention to optimising the code inside the OnCollision…() event handlers as much as possible, and consolidating the collision event data into something more manageable.

    Discard and merge

    The first step was to discard any collision contacts whose separation is larger than a small threshold value, happily this eliminated most of the spurious impact sounds that were being triggered when parts were merely sliding past one another.

    The second part was to merge collision contacts such that for each update, only one contact is considered per Rigidbody pair / PhysicMaterial combination.  This means that, for example, a construction with a large number of parts all made of the same material and all rigidly attached together will only generate one impact or sliding sound.  The most important thing was to perform this merging as efficiently as possible because the OnCollision…() events can be called so frequently; it was crucial to avoid any computation, conversion, GetComponent…() calls, etc. inside the event handlers.

    To keep track of the currently active contacts, the system now uses a dictionary whose keys are a struct containing the two Rigidbodies and the PhysicMaterial (these are all available directly from the data passed into the event handlers).  The dictionary’s values are a struct containing the contact position and normal, the merging happens by only keeping this data for the contact with the smallest separation, the rest are discarded.  Then every update this dictionary of active contacts (of which there aren’t that many due to the merging) is looped over, calculating the required relative velocities, and updating the sliding sounds accordingly.

    To mitigate the OnCollisionStay() performance overhead further, I also added an option in the game-play settings to disable it, for players with low end machines and / or particularly complex constructions.  This effectively disables the sliding sounds, but the impact sounds still work, so it’s not the end of the world.

    Audio materials

    Once ready to trigger an impact or sliding sound, I wanted to add some variety and sophistication to the sounds, while also making configuration easier.  So now, rather than each part explicitly referencing which AudioClips to use, the system automatically maps from the PhysicMaterial to an “audio material”.  Each audio material specifies the AudioClips to be played on impact and during a slide.  The pitch of these sounds are scaled based on the mass of the part that is colliding, and there can be different AudioClips chosen based on the pitch scaling factor.

    I also added support in the audio materials for a “rolling sound” (played based on the angular velocity of a part when it’s contacting something).  This allowed me to make the wheels (which have had sliding and rolling sounds for some time now) use the same unified system.  I do love me some unification!

    AudioSource pools

    Despite the aforementioned reduction in number of collision sounds being triggered, there’s still no real limit on how many could be triggered concurrently.  Also, each part behaviour might have a sound playing (e.g. motor whine, gear whirr, propeller wash, etc.) which is only limited by the number of active part behaviours.

    To bring this situation under control and place a hard cap on the number of AudioSources, I implemented a pooling system.  This pre-creates a fixed number of AudioSources and keeps track of which ones are currently in use.  The collision contact system and the part behaviours can request to play an AudioClip via the pool, and if a free AudioSource isn’t available the request is ignored.  Once an AudioClip has stopped playing, the corresponding AudioSource in the pool is automatically freed up to be available for a future request.

    Damage propagation

    In the game, damage (based on the collision impulse) is only dealt with in the OnCollisionEnter() event handler, not OnCollisionStay().  However I still wanted to optimise this as much as possible, so rather than applying damage directly in the handler, it is now accumulated over an update.  The total damage is then applied once per update (this is where the damage is divided up and propagated out to part attachments).

    I still have some work to do on the damage system but this at least moves the code out of the event handler, and means that if I need to increase the complexity of the damage propagation code, it shouldn’t affect performance too much.  This is a topic I’ll be revisiting in a future update.

  • Dev update Apr / May - part 2

    Linker tool

    I’ve continued work on the linker tool, creating the first pass implementation of an indicator for it, this can be seen above with some pulleys (notice also the automatic belt routing, sweetness!)

    I think I now have a solution for how to handle parts that have multiple linkable behaviours, but I need to start implementing it to really see if it’ll work out.

    Resize indicator

    I’ve added a new indicator to show the selected part’s bounds during resizing, this was particularly needed for parts that can resize along all three axes (e.g. sloped plates) to make things clearer for the user.


    UI stuff

    Up until now each part behaviour has had a specific pre-created UI with all of its elements (key bindings, sliders, checkboxes, etc.) laid out ahead of time.  This was very inflexible and made it awkward to add or change which user adjustable parameters a part behaviour exposed.  So I’ve now removed these hard-coded UIs and replaced them with a generic part behaviour UI implementation that automatically populates itself based on what parameters a particular part behaviour exposes.  This will make adding new part behaviours (and modding support!) much easier in the future.

    I’ve also modified the world tool construction UI to allow for multi-selection, this allows you to select multiple constructions at once and perform an operation (such as delete, freeze, etc.) on them all in one go.


  • Dev update Apr / May - part 1

    Sorry for the radio silence over the last couple of months.  Here’s an update on what’s been happening, there’s a lot to talk about, so I’m gonna break it into two parts!

    Collision impacts, and damage

    I’ve simplified and optimised the construction modification code and the way attachments are handled.  This means that adding or removing parts from large constructions is now noticeably faster, but there’s still more optimisation work to be done in this area.

    Being able to quickly break attachments without causing frame rate drops is a requirement for the damage system, and I’ve been revisiting this too, fixing a few bugs that had crept in.  It still needs more work, but above you can see an example of the damage system in action as it is right now.

    On a related note, the collision impact sounds have been a source of complaint for some, and I agree!  There are too many collision sounds when parts are merely sliding past one another.  I’m currently working on overhauling the collision impact system to make the sounds behave better, and the plan is that this will improve the damage system at the same time.

    Servo and stepper motors

    It’s been suggested that you should be able to set the servo motor target to angles greater than +/- 90 degrees, this was a perfectly reasonable request and sounds like it should have been an easy thing to do!  However, due to the way I was interpolating between the servo’s current and target angle, it would always rotate through the smallest possible angle.  Which meant that for a range of greater than 180 degrees it could easily end up rotating in the wrong direction towards the target angle.

    I’ve now completely re-implemented the angle interpolation code to work a different way, so that it maintains the correct rotational direction.  Now a servo motor’s max angle can be set to +/- 180 degrees.


    Likewise, the stepper motor’s step angle can also now be set up to 180 degrees.  Here are a couple of examples, one with a step angle of 45 degrees, one with a step of 180 degrees.


    I’ve also fixed a bug that would sometimes cause a servo motor’s centre “resting” angle offset to be incorrect after loading a saved game.  And finally, I’ve lowered the minimum speed for servos and steppers to 1 RPM, as I think it’s sometimes useful to be able to go that low.

  • photo from Tumblr

    Belt up!

    Wow, the past few weeks have been rough as far as productivity goes!  First my PC blew its power supply, so I couldn’t work for a couple of days while I was waiting for a new one and then installing it.  Then this week I was totally wiped out by a nasty cold and got pretty much no work done all week.  I guess that’s the way it goes sometimes, really frustrating though.

    Anyway…I have now finished the pulleys and belts, barring a few minor bugs here and there.  The belt rendering is now done and working nicely, the belt automatically routes its way around pulleys based on how they are linked together, and seeing the belt really makes the behaviour of the pulleys appear more convincing.  Have to say I’m pretty pleased with how it all turned out!

    I’ve also added a “pulley whirr” sound that changes based on the pulley’s RPM, and a “belt snap” sound for when the belt breaks (this happens when pulleys move too far from their original position).  These details all add to making the pulleys and belts seem “real”!

  • The last video in this series showcasing GearBlocks player builds from last year, this one themed mostly around cars and trucks.  Thanks again to everyone who has played the demo, given me feedback about the game, and shared their fantastic creations!

  • Here’s part 2 of this player creation’s series, some very cool stuff in this one.  The final part will uploaded very soon.  Enjoy, and thanks everyone!

  • GearBlocks Demo 0.5.6628

    Time for another long overdue demo release, and an update on what I’ve been working on recently!

    Linker tool

    After the last update where I talked about the pulleys and linker tool that I was working on, I have since completed the first pass implementation of the linker tool, and links between pulleys can now be set up by the player (rather than being hard coded).

    However, the linker tool goes far beyond just pulleys and belts, my intention is that it’ll be a general way to associate various part behaviours together (e.g. batteries, switches, motors, and eventually, more advanced control systems), and this introduces the one major wrinkle I still have to figure out.

    The thing is, parts can potentially have multiple behaviours associated with them, which means in theory there could be multiple links between two parts.  I need to decide whether to either prevent multiple links (and in which case, how to do this in a way that makes most sense), or allow for them (in which case, how to represent them to the player via the UI, and if the player should have the ability to create links between individual part behaviours).

    I also still need to add UI indicators, both to show those links already existing, and a link as it’s being added or removed (right now I’m still using debug lines).

    At this point I decided to have a break and work on some other stuff instead, but I will be getting back to the linker tool very soon.

    Third person camera


    I’ve now added third person cameras to the game, both for when the player is walking around, and for when they’re seated.  I debated doing this for a while actually, because I don’t currently have a proper player model, but I finally relented mainly because it’s so much fun to be able to see vehicles from the outside as you’re driving around!

    The player models and animations I’m using are just placeholders that I put in ages ago for the prototype multi-player mode.  Of course this now forces the issue - I now have to decide what the player character(s) should look like, as well as source the models for them, and put in better animations.  Looks like I’ve just created a load of more work for myself!

    Wheel physics revisited


    OK, this is the big one.  It wasn’t supposed to be a big deal, but ended up taking several weeks to sort out!  I wanted to build on the “proving ground” aspect of the desert map in the game, so I added some bumps and ramps (for testing vehicle suspension and so on).  However this highlighted a significant problem with the wheel physics.

    Let’s briefly recap how the wheels worked up until this point.  First the wheel finds where it contacts the ground, by firing a Raycast towards it (perpendicular to its rotational axis) to find a contact position and normal.  Then, it uses a ConfigurableJoint connected to the wheel’s rigidbody, that every update gets repositioned using the contact data, and has a linear limit set up to provide the collision response.  If you’re interested, I did a detailed write up on this a while back:

    Using a Raycast to find the ground contact point was acceptable on terrain with a smoothly changing gradient, but fails once other collision shapes besides the base terrain are introduced (such as boxes, spheres, etc.) for the wheels to roll over.


    You can see here in this example that the Raycast can’t “see” the box, so the wheel inter-penetrates it.  But worse, if the wheel continues to move in the direction shown, the Raycast will eventually hit the box, causing the contact point’s height to change instantaneously, pushing the wheel up with a large impulse.

    So I wanted to come up with a new technique to find the contact point that would meet some important criteria:-

    1. It should ensure that the contact point’s position changes smoothly with no discontinuities.
    2. It should allow the wheel to accurately roll over box, capsule, and sphere colliders.
    3. It should not change the wheel’s behaviour on the base terrain (this can be very sensitive, particularly for vehicles traveling at high velocities).
    4. It should not incur any additional performance cost over the existing solution.

    I experimented with many alternative ideas, including using a bunch of BoxCasts to approximate a cylindrical shape, but everything I tried failed one or more of these criteria.  That is, until I eventually settled on using a single CapsuleCast in the downward direction, whose radius is the same as the wheel’s.

    However this clearly has similar problems to just simply using a CapsuleCollider for the wheel.  For example, if the wheel is tilted to one side relative to the ground, we get a contact point outside of the wheel, coming from one of the capsule’s “end caps”.  To get around this, I effectively clamp the contact point to be within the wheel’s outer rim, as shown in the diagram below (this time viewing the wheel end on):-


    This assumes that the terrain’s gradient doesn’t change too much between the found contact point and the final clamped point!

    Another problem is shown here, where the CapsuleCast would find a contact point on the box in this example, not the point on the ground that we actually want:-


    To get around this, I simply discard any contacts coming from colliders outside the planes indicated by the dashed lines in the diagram above.  So in this example the box’s contact point would be discarded, and the ground contact point is used instead.

    So all in all, this technique is a bit of a kludgy approximation of a true cylindrical collider, but it actually seems to work quite well.  I’m pretty happy with the results!

    Other stuff

    I’ve also done load of code refactoring, bug fixes, UI improvements, rendering improvements (post processing effects, lighting), and other miscellaneous stuff over the past few months.  Check it all out in the new demo build, have fun!

  • Part 1 of a series of videos demoing some of the fantastic GearBlocks community builds from last year.  I meant to do this at the end of the year, but I was working on adding a third person camera to the game and I wanted to wait until that was in, as it better shows off these creations!

    Parts 2 and 3 will be coming soon…

  • Pulleys and belts

    Apologies for the lack of updates lately!  I’ve been working on implementing pulleys and belts in the game, and I was hoping to get them finished before posting an update.  However, as always seems to be the way, they’re taking longer than I expected.  They’re not quite done yet, but I have made enough progress now that it’s worth talking about where things are at.

    Pulley physics

    The first thing I had to figure out was how to physically constrain a pair of pulleys together such that they would transfer motion and torque correctly.  My plan was to use PhysX constraints (as exposed by Unity’s ConfigurableJoint) to accomplish this, in the exact same way I do for gears.

    However, pulleys differ from gears in two important respects:-

    1. Pulleys transfer motion and torque over a distance, through the belt that connects them (unlike engaged gears, which must always be adjacent to one another).
    2. A pair of pulleys linked by a belt rotate in either the same direction or opposite directions, depending on whether the belt is in an open or cross configuration respectively (unlike a pair of engaged gears, which always rotate in opposite directions).

    The first idea I tried was to set up a constraint whose anchor points were positioned on the edge of each of the pulleys, with motion locked along the tangent vector as shown below for two pulleys A and B:-


    However, this didn’t work well at all because the constraint anchor points were separated by such a long distance.  The pulley motion was unstable at anything other than very low RPMs.

    So the next approach I tried was to instead calculate the two circles centered on each of the pulleys, whose radii are in the same proportion as the pulley’s, and whose edges touch each other.  Then I placed the constraint anchors on the edge of these circles, represented by the dotted lines in the diagram below for the two pulleys A and B (again, motion is locked along the tangent vector):-


    Note that these dotted circles are only used to position the constraint anchors, they aren’t visible and don’t interact with the world in any other way!

    This method seems to work pretty well, it also easily allows for a cross configuration belt in a similar manner (by calculating proportioned circles whose edges instead touch in between the two pulleys, and positioning the anchor points where they touch).

    Implementing pulleys in game

    Actually getting the pulleys functional in the game required a lot more work beyond just the physics constraints.  I wanted to allow the player to link an arbitrary number of pulleys together in whatever order they like, to form a chain that determines the route the belt takes through the pulleys.

    For this I created infrastructure to associate or “link” parts together (or more specifically: link their part behaviours together).  This needed to generalise beyond just pulleys, because I plan on also using it to link other parts together in the future (e.g. batteries, switches, motors, and eventually, more advanced control systems).  It also needed to facilitate restrictions being applied (for example, in the case of pulleys, only allow linking if the pulleys are coplanar, and only allow each pulley to be linked to a maximum of two others).

    Based on the order the pulleys are linked together, I also implemented a system to automatically calculate the belt routing (i.e. which side of each pulley the belt should go), which is then used to determine whether to use an open or cross configuration for the constraint between each pair of pulleys, as well as for positioning the visual representation of the belt.

    I wanted pulleys to be able to move around slightly when the construction is unfrozen, but obviously there’s only so far a belt can plausibly stretch!  So I wrote some code to deactivate the belt (both constraints and rendering) when any of the pulleys move too far from their original position, giving the appearance that the belt “broke”.

    This work is complete now, and the pulleys are working in game.  There are still a couple of major pieces left to do however:-

    1. Right now the links between the pulleys are hard coded just so I have something to test with.  I still need to make a linker tool to allow the player to create and destroy the links themselves, as well as a UI to show these links.
    2. Currently I’m just using debug draw lines to visual represent the belt, so I need to implement some code to generate a proper render mesh for the belt.

    But for now, here’s an example of some pulleys linked together, the yellow debug lines showing the links, and the black ones representing the belt:-


    So lots left to do, but this should be really cool once it’s done, and I’m excited about the possibilities that the linker tool will allow for with other parts in the future!

  • photo from Tumblr

    Controls, architecture, events galore…and worms

    It’s been a few weeks since the demo release, so it’s high time I think for an update on what I’ve been working on since then!

    Rotation controls

    As I’ve mentioned in the past, I’m still not entirely happy with the construction interface.  One aspect of this is the way you rotate the selected part while aligning it to another part prior to attaching it.  The current method of using the mouse to rotate around various axes is OK once you get used to it, but I worry that it’s a bit awkward to use, particularly for people new to the game.

    So I tried prototyping a system where you use a key to cycle between the available orientations.  The trouble is, there can be up to 24 possible orientations (e.g. 6 sides on a block, and 4 orientations per side, so 6 x 4 in total).  I found this to be way too many to cycle between and was rather frustrating to use.

    So I tried breaking it up into cycling between alignment axes (e.g. the 6 sides on a block) with one key, and cycling between the 4 possible orientations around the current alignment axis with another key.  This was a bit better than using just one key, but still didn’t feel good to me.  Perhaps this was because it was sometimes hard to tell which way the part had just rotated, or which way it was about to rotate on the next cycle.

    I’m not sure that these ideas offer much, if any, improvement over the current mouse based method of rotating.  Oh well, another failure!  I guess you have to try these things, but I’m gonna leave this for now.

    Game events

    In order to keep the different code modules in GearBlocks decoupled from each other, I used messages (i.e. Unity’s SendMessage) to communicate between them.  I wasn’t that happy with the way SendMessage uses a string lookup for the method name though - not very efficient, and there’s the possibility for name mismatches.

    So I switched all of these messages over to use Unity’s event system.  Events are now specified in interfaces that derive from IEventSystemHandler, and any code that needs to receive a particular event implements the relevant interface.  To send an event to a game object, I use Unity’s ExecuteEvents helper functions.  I created a system that multiple game objects can register themselves with to receive a particular event, to allow for efficient event broadcasting.

    UI events

    Not to be confused with the event system, Unity also has something called UnityEvents.  These are great for when you want to hook up event handlers to events in a scene or prefab, rather than via code.  I found these perfect for my UI code, so I switched this code over from using C# events to instead use UnityEvents.

    Code architecture

    The GearBlocks code was long overdue for some reorganisation, in particular I wanted to divide all the modules up into relevant namespaces.  This is really valuable because it can highlight bad or unexpected code dependencies, and helps enforce a clear code hierarchy.  Once I did this I found one or two suspect dependencies that I had to fix, but nothing too bad fortunately.  It definitely feels better to have the code nicely organised now!

    Worm gears

    Finally, last week I implemented worm gears in the game.  Happily, my plan for how to set up the physics constraints for this worked out first time!  The implementation still needs one or two tweaks, but I’m pleased with how it turned out.  As part of this effort I also simplified the existing gear engagement code somewhat, which should make it slightly more efficient.

  • LEGO Technic 40th Anniversary

    Something a little bit different in this post!  I’ve many happy memories of countless hours messing around with LEGO Technic as a child, and I think this was certainly a huge inspiration for developing GearBlocks.  So, seeing as it’s the 40th anniversary of LEGO Technic this year, I thought I’d pay tribute a little bit.

    In 1977 the first Technic sets came out, although Lego hadn’t coined the term yet, they were known as “technical sets” (or “expert builder” in North America).  There were only four sets in that first year, a forklift, tractor, helicopter, and car chassis.  Only a basic selection of technical parts were available, but they set the foundation for everything that was to come, and many of those original parts are still used today.

    853 car chassis

    This was the largest and most complex model at the time, and featured functional steering, gearbox, and 4 cylinder engine.  It was the first in a long line of car chassis flagship Technic sets that would come in later years.


    I wasn’t lucky enough to own one of these sets back in the day, but I did manage to pick one up on ebay a few years ago.  It’s very basic by today’s standards, but definitely has a charm all of its own.


    So happy anniversary LEGO Technic!  OK, diversion over, time to get back to GearBlocks…

  • Highlighting a few things from the latest demo - how to use the configurable key bindings, and some updates to the lights and differential gear.

  • GearBlocks Demo 0.4.6450

    Well, at long last the new demo build is out!

    SmashHammer Games

    My company is now incorporated, SmashHammer Games is born!  I’m still waiting on the accountant to do his part of the process, hopefully this will be sorted soon, but I don’t think this should hold me back from moving forward with the game in the meantime.

    Bugs and memory leaks

    I was actually ready to release the demo a couple of weeks ago, but I was doing some last minute testing, and noticed some performance slowdowns in certain situations (for example, when highlighting a part).  I also noticed some memory leaks and several bugs that I hadn’t spotted before, not good!

    So I decided to hold off releasing it, to fix these issues first.  This ended up requiring fairly significant refactoring and reworking of some of the code, so took quite a while unfortunately.  Oh well, at least it’s done now!

    Saved file location

    The saved file locations have changed (they’re no longer in game folder). The new locations are:-

    • Saved games: %USERPROFILE%\AppData\LocalLow\SmashHammer Games\GearBlocks Demo\SavedGames
    • Saved constructions: %USERPROFILE%\AppData\LocalLow\SmashHammer Games\GearBlocks Demo\SavedConstructions

    Saved games and constructions from the previous build (0.4.6095) should still load, but you’ll need to copy them into these new locations.

  • Slopes and wedges

    Here’s what I’ve been up to over the last couple of weeks.  I’m still working on the company set up stuff, it’s unfamiliar territory for me, so I had to do a bit of research and get advice from some people.  I won’t bore you with the details, but it seems there’s no getting around the complexities that require both an accountant and lawyer.  This is going to cost me a lot of money, so I want to be sure before going ahead with it!

    Upcoming demo

    I’ll upload the demo update as soon as the company is sorted (should be soon now), but in the meantime, here’s a sneak peak at the changes that will be in it:-

    • Improved builder tool controls and usability:-
      • Changed alignment and attachment indicators for improved visibility and clarity.
      • Improved part selection (restricting selection location to where part can be attached).
      • Better selection rotation behaviour during alignment.
      • Improved part resizing response to key presses.
      • Added part resizing indicator to show available resize directions.
      • During alignment attachment indicators are now shown for any attachments that will be created.
      • Selected construction can now be frozen in place during alignment.
    •  More user configurability:-
      • Configurable key bindings for the various actions in the game.
      • Replaced single graphics “quality level” setting with individual settings for more fine grained control.
      • Added many other options (such as mouse look sensitivity and invert, camera FOV, etc.)
      • Improved sound options (volume controls and speaker configuration).
    • UI improvements:-
      • Improved screen layouts and UI elements.
      • UI is now scaled based on screen resolution.
      • New part and attachment info UI overlays.
      • New game stats UI overlay.
      • Improved in-game context sensitive hints.
    • Updated and improved parts:-
      • Improved part behaviour key binding.
      • Differential gears now have limited slip behaviour, with tweakable “slip limit strength”.
      • Lights can now (optionally) have a key bound to switch them on and off, just like motors.
      • Beams now resizable down to 1 unit in length, and plates from 1x1 to 25x25 units in area.
      • Better wheel friction behaviour.
      • Increased max spring rate and damping values for spring dampers.
      • All part models (except wheels) now textured.
      • New light parts (now with paintable lenses).
      • New seat models (replacing old ones).
      • Wheel rims now paintable.
    • Rendering changes:-
      • Construction materialise / dematerialise effect.
      • Part paint application fade in / out.
      • Corrected part paint colour (de-gamma’d, it now visually matches colour shown in UI).
      • Upgraded time-of-day system.
    • The construction frozen state is now saved / restored from saved games.
    • New and improved sound effects (toolbox, footsteps, ambient loop).
    • Minor tweaks to desert proving ground map.
    • Bug fixes.

    As usual I’ve updated any parts that were already in the demo, but I’m not adding any additional ones, all the new parts I’m making are for the full game only!

    Slopes and wedges


    On the subject of new parts, I’ve now implemented resizable sloped beams and plates, as well as resizable wedge plates.


    Designing their shapes was a bit of a challenge because I had to find a compromise between these three competing requirements:-

    1. Be easily representable by box colliders for efficient physics.
    2. Have plenty of room for attachment points.
    3. Look good when combined with other slopes, plates, etc.

    The wedge shape was the trickiest to represent with box colliders.  I contemplated using a convex mesh collider for it, but I wanted to avoid this as they are generally less efficient for physics, and I also have part intersection tests in the game that only work for primitive colliders.  So instead I created a system to dynamically add box colliders, three for the wedge edges, and then recursively adding more to fill in the wedge interior (the larger the wedge, the more interior colliders are needed).  An example of this can be seen below.


    All resizable parts in GearBlocks use procedurally generated meshes, so I had to implement mesh generation for these new slope and wedge parts.  This wasn’t too difficult but did require a fair bit of refactoring of my procedural mesh system to allow for these more intricate shapes.

    Here’s a comparison of the Desert Buggy construction, the original version vs. one I made using the new slope and wedge parts.


    Not only does the slopes and wedges version look way better, it uses nearly 50 fewer parts than the original!

    In the future I want to add a compound sloped plate (i.e. a “corner” piece), as well as curved beams and plates.  The trouble is, the colliders for these will be even more tricky to set up.  I might need so many box colliders to represent these shapes that it wouldn’t be practical, so I may well have to resort to convex mesh colliders for these.  Anyway, something I’ll come back to later.

    Construction interface problems

    The sloped plate part is the first part in the game that is resizable along all three axes.  Unfortunately this particularly highlights the awkwardness of the current part positioning and resizing interface.  I’m not sure what I’m going to do about this yet, but I think I’ll have to revisit the construction controls yet again.  There has to be a way I can make this better, but I’m just not seeing it right now!

  • So where is that demo update already?

    So, um, that demo release I’ve been promising, where is it you might ask?  The good news is, it’s ready to release (has been for a while actually).  The last thing was to set up an installer for it and that’s all done now (if you’re wondering, I used Inno Setup for this, found it a super easy tool to use, with great results!)

    Unfortunately, I can’t release it just yet as I’m still working on getting my company set up.  This is turning out to be more complicated and expensive than I first realised.  Incorporating the company itself is easy, but because I’ve already been developing GearBlocks for a while, I’ll need to transfer GearBlocks IP to the company, which complicates things and adds to the cost (accountant fees on top of the lawyer fees!)  Anyway, I’ll keep plugging away at this and hopefully get it done in the next week or two.

    In the meantime I’ve been adding more parts - some new sliding rack gears with integrated ball joints / hinges (makes for neater steering systems), more lights, and a seat.  I’ve also implemented limited slip functionality in the differential gear, with configurable “locking strength”, should keep that wheel spin under control!

    I plan on adding various types of sloped / curved beams and plates to the game, this will make constructions look a lot better (and save on the number of parts needed in a lot of cases).  Next week I’ll start work on what should be the simplest of these, a resizable sloped beam.