Eeshlo AO patch, revised

- Ambient Occlusion is a more sophisticated ambient trick, which takes
  nearby faces into account by firing a hemisphere of shadow-rays
  around. AKA 'dirt shader'.
- Eeshlo made it a Lamp type, which doesn't fit well. I've moved the
  settings to the World menu, and let the Material->ambient value control
  the amount it contributes
- currently, the AO value is added/subtracted/mixed with the 'diffuse'
  factor while shading, before it is multiplied with Material color

Buttons are in new Panel 'Amb Occ" in F8 menu. Note:

- "Dist:" by shortening the length of rays you get subtler effects and it
  renders faster too
- "DistF:" the attennuation factor gives control over how the 'shadow'
  spreads out.

Further it's just raytracing, so tends to be slooooow.... :)
Here same tricks as for other raytraced scenes apply, especially try to
keep the environment as small as possible (exclude faces from Octree by
giving them no Material Traceable).

I still have to think over a couple of aspects, will await feedback on it:
- AO color? Now it just adds 'white'
- other sampling patterns? I tried dithering, which was so-so
- method of controlling final 'samples' in F10? Might be useful for other
  oversampling too (area light) to have it reacting to a percentage or so..

1 files changed, 1 insertions, 0 deletions

diff --git a/source/blender/render/intern/include/rendercore.h b/source/blender/render/intern/include/rendercore.h
index 288ff10937f..2daf4c2c299 100644
--- a/source/blender/render/intern/include/rendercore.h
+++ b/source/blender/render/intern/include/rendercore.h
@@ -75,6 +75,7 @@ float spec(float inp, int hard);
 
 extern void ray_shadow(ShadeInput *, LampRen *, float *, int);
 extern void ray_trace(ShadeInput *, ShadeResult *, int);
+extern void ray_ao(ShadeInput *, World *, float *);
 
 /**
  * Apply the background (sky). Depending on the active alphamode and