The way Truce did it is essentially the only way to do it.
How it works:
- You plant a bunch of bricks and the car base and whatever.
- It then grabs all the attached bricks (as in the Duplicator) and saves their relative positions then creates a DTS shape for each brick, and removes the actual bricks.
- The positions are then preserved relative to the vehicle's position and rotation manually using a scheduled tick.
This is the only way to do fully buildable vehicles. There's literally three places here that 95% of the community yells lag at the very mention of (duplicator, DTS shapes, schedules) so that might be a bit of a red flag aye
The way this would be done (I think) if it were implemented in the engine would be localized octrees. So when you plant a brick onto the car it's loaded into the car's octree rather than the global one we build on normally, and when the car moves it's all relative to the car. Essentially like building a single model out of the bricks, or shape compositing or whatever else you'd like to call it. It'd be a hell of a lot of work.
And then there's the issue of complex collision shapes - unless we move fully over to Bullet physics the collisions will be a huge overhead unless it generates approximate shapes which has potential to be buggy as forget. Even then I'm not sure Bullet plays nice with non-convex-hulls so if you had a vehicle shaped like a U the empty part between the tails might be physically solid unless it uses multiple collision shapes.
There's a stuffload of issues no matter how you do it, and several metric forgettonnes of work.
