Dividing bullet shapes optimally

[Game_Starter]

Hi all,

I was wondering what the best way would be to divide a series of bulletTriangleMesh shapes used as “into” collision solids for a terrain. Which would yield faster results: having a few shapes per rigid body, or having a rigid body with many shapes?

I know when using Panda3D’s collision system, since bounding volumes are used for tests, having many collision nodes with a few collision solids each is faster than having a few collision nodes with many collision solids each.

Is this the same for how bullet handles its collisions? I could run my own tests with pstats and such, but I thought it wise to ask if anyone has any experience in this regard first.

Thanks in advance.

[serega-kkz]

For terrain, the answer is unequivocal: to have collision fragments around the character, remove unnecessary fragments at a remote distance.

By analogy:

[Game_Starter]

So the implication is that bullet will do physics tests with everything, regardless of how one puts shapes into rigid bodies, i.e. having a few shapes per rigid body, or having a rigid body with many shapes? It doesn’t have anything similar to Panda3D’s bounding volume tests for collision nodes?

[serega-kkz]

If I answer your question to the point and directly. The BulletTriangleMeshShape class has a bvh parameter, but I don’t know how it works.

This is the answer from the developer of binding bullet.

Panda Bullet

uh, not the modeller, the exporter It might be splitting hairs, but still wrong. The exporter just marks the collision geoemtry. It does not optimize it. Optimization is achived by the way the data is stored in memory and the way it is accessible by the collision detection algorithm. Optimisation is always tied to the actual collision algorithm(s). One example for optimization is the BVH (Bounding Volume Hierarchy) trees which Bullet internally builds for complex triangle meshes. If you r…

[Game_Starter]

Alright, so it seems that it’s best to just have a BulletTriangleMeshShape with many BulletTriangleMesh(es) in it and then to let bullet’s internal algorithms deal with the rest, from what you’ve pointed me to.