On Thu, 17 Jan 2002 13:21:32 GMT, Andre Wesseling wrote:
> I meant coherence in the way Warp understood it. So I wanted to know:
> - Does POV-Ray use any information of one frame to speed up calculation of
>   the next frame while rendering an animation?

In general, no, but of course you can #write variables calculated in one
frame and #read them for the next frame, if your goal is to avoid doing
complex calculations in each frame or if your calculation is inherently
iterative.  Some include files out there (frex, smokegen) use this technique.

> - Is a form of ray coherence used to speed up calculation?

Some patterns do this.  Uppermost in my mind is the crackle pattern, which 
caches the centers for the most-recently-visited part of its perturbed 
lattice in case the next ray happens to hit the same part of the lattice.
This is much faster than recalculating the centers for each ray.

-- 
#macro R(L P)sphere{L F}cylinder{L P F}#end#macro P(V)merge{R(z+a z)R(-z a-z)R(a
-z-z-z a+z)torus{1F clipped_by{plane{a 0}}}translate V}#end#macro Z(a F T)merge{
P(z+a)P(z-a)R(-z-z-x a)pigment{rgbf 1}hollow interior{media{emission 3-T}}}#end 
Z(-x-x.2x)camera{location z*-10rotate x*90normal{bumps.02scale.05}}

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