3d bounding boxes of a model not displaying properly

brainydexter · 04-17-2009, 07:07 PM

I am trying to display the bounding box spheres for all the meshes in the model.

I have them displaying, but for some reason(which obviously I don't know), they seem to be just out of place. Well, I'll put in my code first and then ramble.

Loading the <int, BoundingSphere> dictionary:

Code:

Model.CopyAbsoluteBoneTransformsTo(transforms); 

foreach (ModelMesh mesh in Model.Meshes)
{
   BoundingSphereDictionary.Add(mesh.ParentBone.Index,mesh.BoundingSphere);
}

Updating BoundingSphere dictionary:

Code:

Dictionary<int, BoundingSphere> tempBSDictionary = new Dictionary<int, BoundingSphere>();

            foreach (int index in BoundingSphereDictionary.Keys)
            {
                BoundingSphere bs = BoundingSphereDictionary[index];

                Matrix transformation = transforms[index] * Matrix.CreateTranslation(Posn);
                bs.Center = Vector3.Transform(Vector3.Zero,transformation);
                
                tempBSDictionary.Add(index, bs);
            }
            BoundingSphereDictionary = tempBSDictionary;

What I am doing here is, transforming each sphere by the position in the world and further transforming by the internal transforms[parentbone.Index]

And, the Draw Call:

Code:

foreach (int index in BoundingSphereDictionary.Keys)
            {
                foreach (ModelMesh mesh in boundingSphereModel.Meshes)
                {
                    foreach (BasicEffect effect in mesh.Effects)
                    {
                        effect.View = view;
                        effect.Projection = projection;

 effect.World = 
Matrix.CreateScale(BoundingSphereDictionary[index].Radius) *
          //Matrix.CreateTranslation(BoundingSphereDictionary[index].Center);
transforms[index] * Matrix.CreateTranslation(Position);   
                            
                    }
                    mesh.Draw();
                }
            }

Now, this works fine! Instead if I un-comment the Matrix.CreateTranslation(..)
and comment the manual translation done via

Code:

transforms[index] * Matrix.CreateTranslation(Position);

The spheres are not the same. They are bigger in radius when I use the boundingSphere.center to translate the spheres than when I use the transforms[index] * ...

I am essentially doing the same thing in update as well, but still I dont understand why is there, this discrepancy in the output ?

Can somebody please help me out with this.

Also, if you want me to upload the code, I can do that.

Thanks