XNA- Rotating around another model

Question

Lets say I have a model with multiple meshes. Mesh A is at position PositionA = new Vector3(5,0,10). And mesh B is at position PositionB = new Vector3(7,0,9). How can I rotate mesh B around meshes A pivot point, or its centre?

Answer 1

In Xna, you can orbit positionB around positionA like this:

Matrix orbit = Matrix.CreateFromAxisAngle(someAxis, someAngle);
positionB = Vector3.Transform(positionB - positionA, orbit) + positionA;
MeshBworld.translation = positionB;

where someAxis is a unit length vector representing the direction of the pivot axis and someAnglerepresents the amount of single frame orbiting rotation in radians. MeshBworld is simply Mesh B's world transform... whatever you've named it.