Getting coordinates of lowest point on object

[Nick]

Hi all, I'm trying to work out how I can compute the coordinates of the "lowest" point in an object/shape in the world, by which I mean the point with the lowest y-coordinate.

Now, clearly I can get the lowest y-coordinate from the AABB, but I can't see how I would then proceed to get the x- and z- coordinates.

Can anyone point me in the right direction?

[Ripiz]

I think you'll have to loop through every vertex and compare to find lowest one.

[Erwin Coumans]

It depends on the collision shape type. For convex objects (btBoxShape, btSphereShape, btConvexHullShape, btCylinderShape etc), you can use the 'getSupportingVertex' method:

Given a convex shape and a world transform, you can try something like:

Code: Select all

btVector3 direction(0,-1,0);
btVector3 supportAxisInA = (direction)* worldTransform.getBasis();
btVector3 pInA = convexShape->localGetSupportVertexWithoutMarginNonVirtual(supportAxisInA);
btVector3  pointInWorld = worldTransform(pInA);

For compound shapes and triangle meshes, it requires a bit more work.
Thanks,
Erwin