bagginsbill opened this issue on Oct 25, 2007 · 273 posts
bagginsbill posted Sat, 31 May 2008 at 10:39 AM
I have two identical dimpled spheres. They differ in which direction the dimple is occluded. On the left the ground is occluded and the sky is not. On the right its the opposite.
Now, given that the geometry is identical, Poser AO calculates a generic darkening for the deepest part of the dimple that is dark. It is the same for both. This is wrong.
AO is a cheat. It is not a perfect substitute for a true global illumination model.
What SHOULD occur here is the dimple on the left should not be so dark. Why? Because the sky is NOT occluded, and most of the light comes from the sky. But that's not how AO works. AO doesn't care where the light really is coming from in your IBL. It just says - here is a deep recessed spot - I shall make it dark. Even if the recess faces straight at the brightest part of the sky, it will be the same amount of dark.
So what is the solution? The solution is to not use Poser.
OK that's an asinine solution. :) What is the Poser solution, then?
Well the solution is to make some more assumptions and make some more cheats.
Assumption one - The sky is brighter than the ground.
Assumption two - Apollo's head is right-side-up.
Ok given these assumptions, we can say which part of the ear should not be so dark (because it faces up.) We make a map that prevents AO from fully darkening that spot.
Are we limiting our situation - sure. Basically we're making it more correct for some situations, and less correct for others (Apollo is standing on a 70's disco glowing dance floor, or Apollo is hanging upside-down from a tree). If it is more correct for YOUR situation, then it is a good thing. If if is less correct for YOUR situation, but more correct for 80 other people, it is still a good thing.
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)