Fugazi1968 opened this issue on Aug 06, 2009 ยท 96 posts
bagginsbill posted Thu, 06 August 2009 at 9:39 PM
No, bump maps do not disturb the normal on Y. They disturb the virtual position, which is also going to move a point in 3 dimensions. They indicate the virtual position of a displaced surface with respect to the original surface along the original surface normal. Then the gradient of this new virtual surface is calculated, producing new normals, which are substituted back to the original surface.
In both cases, 3 values are altered. For bump, it is position, which results in new XYZ vector components for the normal.
The math is straightforward, even if not everybody here believes me. I got an 800 on my Physics SAT, and got an A in calculus at MIT, if that helps anybody trust my word on this.
Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)