Panda Bullet

[enn0x]

@Anon

@enn0x

Your viewpoint is, well, wrong. Your 3d modeller doesn’t create anything optimized for collision detection

uh, not the modeller, the exporter

@drwr

CollisionPolygons are many times faster than the exactly equivalent Geom, just because the data structure of a Geom is optimized for render data, whereas the data structure of a CollisionPolygon is optimized for collision data.

Basically, collide-with-geometry is only provided as an option to facilitate development, so you can do a quick-and-dirty collision against your visual geometry for cases when you really don’t care about performance. But if performance matters to you, you should always use CollisionPolygons.

Especially if the geometry isn’t even intended to be rendered. In that case, you have no excuse, and you should have created CollisionPolygons in the first place.

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 read the text by drwr which you quoted, then you will see that drwr also talks about the data structures used for storing the geometry.

This is in on way related to file formats. File formats, like egg, hold just the geometry. It is up to the classes managing the information loaded from files to store and provide the data in optimized ways.

@rdb:
Seem like the confusion originates from blurry distinction between “rendering geometry” and “collision geometry”, caused by Panda3D supporting collision detection against visible geoemetry. Which is, imo, a very nice feature for rapid prototyping. Do you have a suggestion on how to best summarize this? I obviously don’t find the right words to explain it. Maybe we can add a paragraph in the manual page panda3d.org/manual/index.php/Physics, since this is not related to Bullet only.