Sphere mapping

Is there a difference between the sphere mapping in Microsofts software implementation and the sphere mapping in NVIDIAs drivers? I see different reflections (rotated 90 degrees) in this implementations.

Are there additional parameters to adjust it or do I have to adjust the normal vectors manually in the different implementations?

Anybody has similar experiences with other graphic accelerators?


Yup I’ve got a similar prob. Doing some sphere mapping and on a TNT2 its beautiful. But on a pc with nothing that uses the basic MS drivers its as if the map is stretched vertically not horizontally?

Still looks ok but not as it should.

On the subject of sphere mapping. I was wondering if anyone else wanted to enact sphere mapping in such a way that the reflection texture coordinates are calculated based on a reflection coming from a source other than the camera itself as OpenGL does when it generates texture coordinates. I would like to do this as I am experimenting with having the camera chase an object. It orients itself directly behind the object (a hover car.) I would like it so that when I turn the car the reflection map changes along with the car’s rotation as it appears when I rotate the car and the camera is in a fixed location.

Right now the map stays exactly the same since the camera aligns itself perfectly behind the car (it moves slightly, but not enough to get the effect I want.)

I know what the sphere mapping formula is and I believe I can probably calculate the texture coordinates myself, but I figure if I let OpenGL do it, it may be faster.

Has anyone else messed with this? Could the GL_TEXTURE_MATRIX have something to with it?

Daniel Piron

If you multiply the texture matrix with the camera transform (or the inverse, I can’t figure it out right now), it might do the trick.

(otoh, it might not…