cubemap projection question, could be a bug?

General TouchDesigner Discussion
1

I might not be looking at this correctly, but when I use a cubemap texture on a sphere, it seems like the reflection is a 360 degree projection instead of 180, i.e. I can see reflections of objects that should be behind the sphere.
MD

edit - It may be related to this in the vertex shader:

vec3 texgen(vec3 camVector, vec3 camSpaceNorm) {
return mat3(uViewMatrixInverse) * reflect(camVector, camSpaceNorm);

in the orange book, it looks more like this: (pg 267 2nd ed.)
vec3 texgen(vec3 camVector, vec3 camSpaceNorm) {
return reflect(camVector, camSpaceNorm);

2

Hmm, can you send an example? I just looked at a few cases and it looks correct to me.

3

ok, I am wrong about the change to the code, that just puts it into worldspace.
I just looked at it again, and it has to do with the way the cubemap works. In my example, when you look at the sphere dead on, you should never see more than 5 walls of the cube. What I have done to get what I think is a more realistic result is to multiply the normal by a constant to clip off the infinite reflection around the edges.

vec3 envMapCoord = texgen(-cameraVec, uFactor*camSpaceNorm);

values around 1.5 for uFactor seem pretty good. I guess it works a bit like a refractive index, but I am way out of my league here

so not a bug, just the way it works…

MD
cubemap_compare_v1.1.toe (5.86 KB)

4

Ya it depends how close you are to the sphere. If it’s far enough away you’ll get super shallow reflections that will be reflecting the 6th face.