Mike Williams wrote:
> If this effect is causing you problems in a real scene, here's really
> ugly workround that will get you going:
> 
> #declare my_isosurface = isosurface { ...
> 
> object {my_isosurface no_shadow}
> object {my_isosurface scale 0.999}
> 
> The scale value plus the accuracy value should add up to 1.0 or less, so
> scale 0.999 works with your accuracy value of 0.001. If you want more
> accurate shadows you can use accuracy 0.00001 and scale 0.99999
> 
> Obviously, in your test scene there's no need for the shadow casting
> copy, because the shadow isn't case on anything other than itself, and
> it's those self shadows that are the problem.
> 
Thanks to you and Slime for taking a look.  The first image is a test
from the actual application.

The second is from a quick attempt to apply your workaround but I don't 
think I quite grasped the concept.  Anyway it is apparently to no avail. 
  The actual isosurface function is an IC_Sor definition from 
iso_csg.inc then with some pigment functions combined. So that may be 
why I got the same result. (But as I tried to understand the thinking 
behind your workaround it made me wonder if the threshold value might be 
used.)

Anyway if it doesn't work I'll just have to try another approach.  But 
it makes me wonder why these artifacts don't appear in the iso_wood 
macros for instance.  I can't believe I am the first one down this path.

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