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View Full Version : evironmental bump mapping what's this?



ugluk
06-07-2010, 08:16 AM
I've seen many references to environmental bump mapping, but I've never seen anything actually saying what it is.

It seems to me, as if environmental bump mapping is just the usual cube map or sphere map texture sampling with the bump map also being a cube or sphere map? Can you please give a reference to a proper ref/tut and/or give a simple explanation? Also, how to generate a cube/sphere bump map?

dorbie
06-07-2010, 12:44 PM
EMBM (environment mapped bump mapping) is environment mapping where the reflection vector (as determined by the view vector position and normal) is calculated based on a surface normal that has been peturbed by a bump map.

So reflective wrinkly surfaces such as ripples on water are an example of where this technique is useful.

There are several methods of environment mapping, cube mapping seems to be the standard on modern hardware.

EMBM causes some technical challenges for hardare developers because there is a dependent texture read (one texture coordinate is not known until another texture result is fetched) but that's easy nowadays the second problem is that the derivative of u & v are unpredictable (vary with local dependent reads) so hardware developers tend to shade in 2x2 pixel quads and compute derivatives using adgacent results, even for less complex cases.

ugluk
06-08-2010, 01:08 AM
I have difficulty finding a precise definition, let alone anything else on the technique. Maybe you can suggest some tuts/refs or sites?