Bounding Box Size Incorrect

[Mr_Ridd]

Hi

I am busy implementing OgreNewt and I came across a bounding box issue.

I created a scenenode and showed the bounding box and the size of the bb was quite a bit greater than the actual mesh. The size also got worse as the scenenode moved.

To test I put two tests together and I got the following results. The two nodes in the image are straight OGRE nodes with no physics.



The code is as follows:

Code: Select all

SceneNode* n1 = mSceneMgr->getRootSceneNode()->createChildSceneNode();
		Entity* e1 = mSceneMgr->createEntity("sadas1", "crate.mesh");
		e1->setNormaliseNormals(true);
		n1->attachObject(e1);
		n1->setPosition(Vector3(1300, 350, 1300));
		n1->showBoundingBox(true);

		n = mSceneMgr->getRootSceneNode()->createChildSceneNode();
		Entity* e = mSceneMgr->createEntity("sadas", "crate.mesh");
		e->setNormaliseNormals(true);
		n->attachObject(e);
		n->setPosition(Vector3(1280, 350, 1300));
		n->showBoundingBox(true);

The second mesh is rotating.

As you can imagine this gives horrible results when applying physics as the objects elevate off the ground. Are there any fixes for this or is this a bug?

The meshes are from the OgreNewt demos.

Thanks

[Van]

You will need to confirm this but I recall that the bounding box is the actuall bounds of the Entity and does NOT take into account the scene node scale.

This was a bug in OgreNewt I thought was corrected. In all cases, the itteration through the ogre entity should be multiplied by the scene node scale to yield the correct collision mesh.

[haffax]

Not a bug. This is a padding in the Mesh's AABB. You can set the padding factor to 1.0 prior to loading your meshes using MeshManager::setBoundsPaddingFactor.

Also note, that the bounding box is axis aligned, so if the mesh is not parallel to the world's main axes, the box grows, so that all fits still in. This is what happens with your second box.
The reason for this is, that an axis aligned box is *much* faster to operate with compared to an oriented bounding box.

This only applies to the box in Ogre. Newton's box collision is oriented and behaves as wanted.

[yuriythebest]

in your 3d program try setting the pivot point to the exact center of thje mesh

[Mr_Ridd]

Thanks a lot guys, helps me a lot.

[Mr_Ridd]

I tried to set the padding to 1 and that make the bounds even bigger, setting it to 0 put it back to the way it was originally.

Is there something I'm doing wrong?

Code: Select all

MeshManager::getSingleton().setBoundsPaddingFactor(0.0);

[yuriythebest]

just a wild guess but have you tried setting it to a negative amount- hopefully that will not give an error.

[lewap]

setBoundsPaddingFactor - add a given value not multiply.

But I have the same problem with bounding boxes. Does anybody found a solution ?