Hi all, over the holiday period I decided to take some time out to try an experiment: attempt to add undo functionality to the game.  Specifically, implement a command history, to which a command would be added for each tool action (e.g. select, move, or attach parts, apply material or paint, etc.) and then allow the player to undo or redo the commands in that history.

The game’s tools were not originally built with this in mind, but the code is reasonably well structured so I thought it might be possible.  The initial prototype turned out to be promising, and showed the potential improvement to usability this would bring.

Well, I couldn’t resist seeing this through to completion, and so that’s what I’ve been working on for the past few weeks.  It required substantial refactoring of some of the tool code, and took a while, but the results are well worth it I think.

Here it is in action, I’ve exposed the command history to Lua scripting, and made a script mod that shows the current list of commands:-

Implementation details

Rather than store an absolute snapshot every time something changes, the commands in the history store relative deltas.  A command keeps a record of the change that was made by a tool action.  This means implementation was kind of an “all or nothing” prospect: all tool actions must be accounted for the command history (in the right order!) for everything to work properly.

Here are the commands I ended up with, these are added to history when…

• Select tool: …a tool is selected (some actions are only valid when the
  correct tool is active, so this must go in the history).
• Select parts: …any frozen parts are selected or deselected.
• Select pivot: …a pivot point is selected, which detaches all the selected part(s).
• Move / resize selection: …the selected part(s) are translated, rotated, or resized via manipulators.
• Replace attachment: …an attachment’s type is changed.
• Lock attachment: …an attachment is locked or unlocked.
• Delete attachments: …attachments are deleted (whether directly, due to the
  selection being detached, or due to a part being destroyed).
• Spawn / destroy construction: …a part / construction is spawned or destroyed.
• Freeze construction: …a construction is frozen or unfrozen.
• Swap material: …a material is applied to a part.
• Add / remove links: …link(s) between link nodes are added or removed.
• Apply paint: …paint colour is applied to a part.

The command history has a buffer containing references to the added commands, in the order they were added.  This allows for the commands to be undone in reverse order, and redone in forward order.

The history maintains an index of the last undone command, and if a new command is added, it will go into the buffer at this point.  Any commands that came after the one most recently undone will be lost.

The buffer is a finite size (currently 256), if a command is added to history and it’s full, the oldest command is removed.

New demo

So, the game now has full undo / redo capability (using Ctrl + Z / Ctrl + Y).  This is a feature that this genre of game really should have, and I think it was worth making the effort to get it done.

There are still a couple of issues left to deal with, but it’s now in a usable state, so I’ve just updated the demo to include it.  A lot of code had to change, hopefully I haven’t introduced any glaring bugs, it seems stable so far.  Give it a try and let me know how you get on with it!

Hey everyone, I’ve just released another demo update, which features a lot of the things mentioned in the previous dev blog post, along with many bug fixes.

Release notes:-

• Tools:-
• Implemented new grabber tool, for dragging and shoving objects.
• After detaching selected parts, attachment types are now restored if those same parts are reattached.
• Tools now only highlight parts relevant to them.
• Part behaviours:-
• Electric motor modified to prevent reverse spin up after coming to a stop while braking (until control is released), also now has separately configurable braking torque.
• Added braking to “Car Wheel” part, controllable with a bound key.
• Differential gear’s locking (i.e. slip limit) can now be turned off with a bound key.
• Light’s brightness now configurable in part behaviour settings.
• Implemented analog joystick binding for part behaviours.
• Activation state now serialized to saved constructions / games.
• Added option to label a part’s function in the construction controls UI overlay (see below).
• Physics:-
• Replaced “continuous contact detection” game option with “contact detection mode” scene setting.
• Rotary bearings now have small angular drag (to simulate friction).
• Player seating:-
• Player can now leave seat with jump action (i.e. pressing Space).
• Improved player positioning after leaving a seat.
• Added new chase camera mode, available when player is seated.
• UI:-
• Added new construction controls UI overlay, shown when no tool is selected.
• Improved and expanded help UI screen.
• Removed player stats (speed, etc.) UI overlay, this will be replaced with a script mod in the full game.
• Removed old “Corrugated Steel” plate part.
• Bug fixes.
• Upgraded to Unity 2020.3.42.

Hey all, I decided to put out another demo update, as I’ve fixed quite a few bugs since the last one, it also has some of the new features I mentioned in the most recent dev blog post.

Release notes:-

• Implemented “attachment locking”, a way to prevent attachments from being modified or deleted.
• Added a compass UI overlay.
• Added “how to” pages to the help UI screen.
• Various other UI tweaks and improvements.
• First pass of localisation support.
• Bug fixes.
• Upgraded to Unity 2020.3.38.

Hi all, another minor demo update is out now with some small usability improvements and visual changes to the in-game maps.

Release notes:-

• Minor usability improvements:-

1. Builder tool actions (unfreeze, duplicate part, and delete part) now work even when targeting a manipulator handle.
2. Unfrozen (individual) parts can now be directly deleted, without having to freeze them first.
3. Move manipulator part resizing now works even when “transform” and “resize” actions are bound to the same keys.
4. When no tool is active, the targeted part is only highlighted if it has an activatable or tweakable behaviour.

• Improvements to the “desert proving ground” map:-

1. Implemented height based texture blending in the terrain shaders.
2. Replaced terrain textures.
3. Added grass and trees.
4. Implemented a rudimentary “weather” system that adjusts the sky between clear and cloudy.
5. Improved atmospheric scattering to better visually blend between the terrain, distant terrain, and sky.

• Improvements to the “flat plane” map:-

1. Expanded its size to 8x8km.
2. Replaced floor texture.
3. Replaced sky with an environment cube map.

• Raised boundary height to 2 km in all maps.
• Bug fixes.
• Upgraded to Unity 2019.4.38.

Just put out another small demo update with fixes to prevent cases where interpenetrating parts could be attached together.

I also expanded the desert map to an 8x8km playable area (12x12km visible), and added a simple visualisation of the map boundary.

Another minor demo update is now out with tweakable wheel friction and control wheel torque, and a few other improvements and fixes!

Release notes:-

• Added sliders to the wheel’s part behaviour UI for setting its longitudinal and lateral friction coefficients.
• Added a slider to the control wheel’s part behaviour UI for adjusting its torque.
• Reimplemented options serialization code so that saved settings will persist across future version updates.
• Added button to the controls options screen to reset key bindings back to their defaults.
• Added multiple player spawn zones to the “desert proving ground” map (spawn position chosen from a random zone when starting a new world).
• A construction’s position is now reset if it goes out of bounds of the world map.
• Bug fixes.