CollisionShape is overriden

Troubleshooting physics
1

Hey Guys,
I have the following problem: I have some static objects (100 chairs) for which I don’t need some complex collision shape but only a box shape.

What I do now is:

CollisionShape box = CollisionShapeFactory.createBoxShape(spa);
spa.addControl(new RigidBodyControl(box, 0f));

Afterwards I have a general “new RigidBodyControl()” on the “Scene”, to add all the walls, stairs and such.
For some reason this already drastically improved performance (less cpu stress).

If I now enable the physics debug view I still see some complex shape. I thought the “general” shape would create a CompoundShape and add those previously manually created objects but it doesn’t.

2

Why would it? It does create a compound shape but that is as “complicated” as the single shapes its comprised of.

3

Yeah but it seem’d to recreate existing shapes for children.
I’ve found out something different, though.

The above code does not improve perfomance. I made all NPCs static in the same commit, which was the perfomance improve, but I guess this is just because the physics were faster than the vsync, so it’s just a race condition.

What does createBoxShape() exactly do? could it create several sub shapes? I expected it to be one huge cube with the dimensions of my spatial.
Is there a way to get those “half-extents” btw?

4

createBoxShape is recursive, yes. And all of these methods just take the scenegraph you give to them and create a collision shape for it, its just a helper method, not magic. You can just create collision shapes manually btw. Half-extents are just a vector from the center of the box to a corner.

5

But they could check if the spatial already has a PhysicsControl and then simply merge the CollissionShapes? (Or does it and I simply do something wrong?)

This is a problem for me if I have more complex spatials (blender models). The only way I could think of is iterating over each Vertex and then take the one which is the farest away from the center.
Since the SceneComposer needs to perform that task aswell, I wonder if there is some helper method?

6

It doesn’t, as I said its a simple helper method to create a collision shape for a graph. Such a method shouldn’t simply remove PhysicsControls the user added. (Which it would have to if it was to use its collision shapes and add it to a new PhysicsControl in a compound shape). The code isn’t complicated, just make your own helper method that does whatever you want (which I intended to imply by saying that you can just create collision shapes yourself and are not bound to the CollisionShapeFactory).

The BoundingBox of a spatial has this information, thats what createBoxShape uses.

7

Okay fine,
For the BoundingBox:
I can’t assume each BoundingVolume to be a BoudingBox I guess?
So could I use bv.distanceToEdge(bv.getCenter());? Which edge would be chosen then?

And how can I merge different meshes (recursively all meshes of that Node)?
I read about appending the buffers, but it would be easier to have some Mesh.combine() :slight_smile:

8

You are aware that you can look at the source of every jME class by just right-clicking it in the code editor?

9

I didn’t know. I actually always googled and then found some google code stuff.^^

By investigating, I guess it’s:

GeometryBatchFactory.gatherGeoms(spatial, list);
GeometryBatchFactory.mergeGeometries(list, myMesh);
myMesh.getBounds();