Bump Map Problem

I know it may sound odd, but this behavior is by design. Personally I cannot explain this design decision, feel free to ask Vladimir about that.

Thanks to Vladimir, I understand the problem now. The issue is the limited dynamic range of the gray scale bump map. If changing the surface height in the Lighting tab affected the bump map, then for large heights, you would see noise, posterization effects, and, possibly, clipping. It is important to note that this issue is not unique to Filter Forge. It is the primary reason that most modern game engines have switched to normal maps. Although manually adding height features to a normal map is not as straightforward as tweaking a bump map, there is a handy little programs that helps a lot. See: nDo.