Compound Collision Shapes howto?

The story goes I’m working on an indie game and have chosen COLLADA for an intermediary model format, Bullet for physics, and becuase it just made sense, Blender for most of my modeling. I am a programmer but decided to figure out all the needed features of blender just to make sure that it will support all of the things I need. So far that’s true, I can do lot’s of great things however I have hit one snag. I can’t seem to get multiple collision shapes working. Say I have a bottle (there are better examples but this was the first that came to my head.), I would want to model the bottle in the physics engine as a cylinder for the base, and a cone for the top, which simulates the curviture enough for my use. But I can’t seem to do it unless I make two separate meshes under two separate objects, give them unique collisions shapes, or the cylinder and the cone, and them put them together using a rigid constraint. This would work however it adds extra overhead and is really just a hack. Bullet, Blender, and Collada all seem to support multiple physics shapes per object, however blender is the only one I can’t seem to figure out. Any help would be appreciated greatly.

by the way: Blender owns!

Make a single object and use Bounds-ConvexHullPolytope
It works fairly well, maybe enough for you.

When I export a mesh with a convex hull polytope bounds with COLLADA 1.4, it just points to the geometry for the mesh, which is not even a convex hull polytop.

Try to “talk” directly to Erwin, Bullet developer at the Bullet site, maybe?!

un-parent the objects, select your parent, press ctrl-a and alt-g, select your child, press ctrl-a and alt-g, parent th child to the parent, move and rotate the child till it’s in the right spot, make the child not even an actor, don’t press the “compund” button, press compund on the parent.

I realized that if you’re working with cones and cylinders, ctrl-a will probly screw up the collisions, so cut the control a crap, and just add your cylinder and cone from the top view. then resize them in edit mode if needed, but don’t rotate anything yet. Now alt-g both objects and parent them, then move an rotate the child to the right position. Now you can move and rotate the parent all you want, just don’t scale anything or ctrl - a it

well, If you like Bullet , Blender and Collada, You might want to try Crystalspace.

It uses all 3, and is very good at it :smiley: