On 3/9/2011 9:34 AM, Trevor G Quayle wrote:
> Robert McGregor's recent comments on using AO for grime layers tweaked me
> thinking about how to achieve an object pattern that could do this.  I was
> thinking along the lines that we have slope and aoi patterns for example that
> depend upon the object surface itself, would it be possible to have a pattern
> that basically for any given surface point, shoots a trace ray or the like,
> normal out from the surface and returns the value or a function based on
> distance to self-intersection, likely an inverse function ranging from no
> intersection=0 (1/inf=0) to immediate=1 (0/1=0).

IME, the best (not to mention the most accessible) way to do this is to 
use a proximity pattern, which is basically just an object pigment 
blurred in 3D space. The advantage of using proximity patterns is that 
you can obtain *outside*edge* data as well as inside edge data.

Any other AO-like ray tracing/casting method would require some new 
routines to be added into POV's rendering core... but I could be wrong. 
(anything can be done if you're willing to wait through a long render)

Look for anything related to "proximity patterns." It might not be the 
most efficient method for adding "crevice grime" to objects, but you can 
always bake the effect into meshes using POV-Ray 3.7b.

Good luck!

Sam

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