in curvytron your trail grows behind you as you go, so on each frame most of active players trail "capsule" 3D geometries have changed.

I started by blindly recalculate every geometry on every frame, work well enough for a time but I think you can see the optimisation problem coming...

On each frame the trail gets only 1 new point and the rest of its points (dozens) has not changed, yet you recalculate every segment vertices (and normals, etc) for every point, just to add one new segment at the end and finally add the half-sphere cap. And this is done by Three.js: so by the CPU, not in GPU yet.

What I did was write a dynamic capsule geometry, with pre-allocated geometry buffer and the capacity to add 1 point at each frame by just filling the missing vertices, normals, etc fo the point. Resulting in a massing performance improvement.

Side note: when the player stop "drawing" and leave a hole behind, the detached trail become inactive and just stop being re-computed at each frame.