Gradient Bump is intended to take the old Poser 3 / 4 style .BUM maps. I don't believe these are quite the same as normal maps, since normal mapping requires three colour channels and .BUMs have only two. The blue channel is unused; or rather, it produces unusual results if you hack one to add stuff to it. There is a lot of confusion over bump maps. It is basically a "perturbation" in the surface normal, which gives the illusion of surface features; or to put it another way, it's affecting the way the lighting hits the surface. Any more detail would probably require equations, and having spent last evening trying to help my son with his maths homework, I feel unwilling to go there.

Quote - And why do people just greyscale the texture and use that as a bumpmap?

I deleted my first answer since it would have required a language advisory. :) Possible answers are: - Because "everybody else" does it, so it must be right. - Because it doesn't look unreasonable, in some circumstances, so it must be right to do it all the time. - Because they want to fill up your disk with useless files. :) ----- Edited to say: Bah. ghonma typed faster than I did. :P