flutter3d_physics library

Collision, character movement and cloth, with nothing above them.

Shapes that overlap exactly, a broadphase over a uniform grid, sweeps and rays that do not tunnel, and a controller that walks, jumps, climbs a step and rides a lift. Nothing here knows what a monster is, what a level is, or how a frame is drawn.

src/cloth/ was its own package once — an XPBD solver reacting to this package's own CollisionShapes and depending on nothing else, which made "a package of its own" the only reason it stayed apart. It moved here rather than the other way round because collision is the older, larger half and cloth is the one thing that only ever pushed against it.

Plain Dart. No Flutter and no flutter3d, so the whole of it runs under dart test on the VM. That is not tidiness: the failures this code has are the ones that happen once in a thousand steps — a body that ends up inside geometry, a sweep that passes through a wall at a high speed, a platform that stops carrying its passenger — and finding those means running thousands of steps in a loop, which is possible exactly because none of it needs a device.

Layers are numbers here, and names somewhere else

A collider carries a layer and a mask, and two of them meet when each is in the other's mask. Which bit means what is a game's business: this package shipped as part of one for a while and its layer list named monster, pickup and projectile, which is exactly the knowledge a collision world must not have. Layers.all is the only constant left, because "every bit" means the same thing in every game.