HankR wrote:If I understand correctly, the problem is not so much the normal map, which can be created in a straight-forward way from topographic data, but rather the albedo (color) map, which ideally should not include any shading due to topography. Unfortunately, most surface maps incorporate topography via "shaded relief", which needs to be eliminated to make a useful albedo map.
In principle, if you have an accurate normal map, and you know the direction of the illumination used for the shaded relief, it should be possible to remove the relief shading from the surface map, producing a useful albedo map. I don't know if anyone has tried this, but it would be an interesting experiment.
- Hank
Yes I did plenty of experiments along these lines. The idea is pretty obvious;-). So far my results were never too satisfactory, despite going into the right direction.
There are simply too many parameters to fiddle.
a) azimut of sunlight. That is often quoted (SpaceGraphics RedMars, for instance: 60 degs).
b) Altitude?
c) Rescaling of compensating bumpmap
Bye Fridger