make a plane and UVing a texture on it
make a material with this texture and press “nor” button to make bump mapping
render it
now in UV editor, mirror the UV
render again
now the bump is inverted
why? is this a bug?
I wouldn’t consider this a bug. When you mirror the UV map you are in effect looking at the back/other side of the face ie. the UV coordinates are in the same relation as if you did a “from window” from the back/other side of the object. It therefore makes sense that the bumpmapping would be inverted.
GreyBeard
NO
the bump texture only a b/w image, that stores “heights”
I think this is a very bad thing in Blender.
This is indeed strange behaviour, UVs don’t have a ‘backside’. I can’t reproduce this with a simple b/w texture on a cube.
Could you post a sample .blend somewhere, or report it in the tracker (with a sample .blend)?
http://projects.blender.org/tracker/?atid=125&group_id=9&func=browse
blendix said
This is indeed strange behaviour, UVs don’t have a ‘backside’. I can’t reproduce this with a simple b/w texture on a cube.
I know that UV’s don’t have a backside. I merely pointed out that mirroring the UV’s creates coordinates in the same relation to each other as mapping the backside of the original plane. I can therefore understand why mathematically the program has the effect described by endi.
Whether this effect is desirable or not is a different question – the program is not consistent in that while bump mapping a plane depressions remain depressions no matter which side of the plane faces the camera. Consistency with the effect endi describes should show bumps when viewing one side of the plane and depressions when viewing the other. This lack of consistency could indeed be construed as a bug.
I can reproduce endi’s problem with a cube if I do a “from window” UV mapping and then mirror the points. Pressing the nor button again (turning it yellow) inverts the bumpmap again, I don’t always remember this being the case but maybe I’m wrong.
GreyBeard