On 10/23/2014 10:30 AM, fuglede wrote:
> William F Pokorny <ano### [at] anonymousorg> wrote:
...
> Makes sense. For the pigment ones, I need to apply different ones to the ramps
> and the disks; if I put the "filter" from the disks on the ramps, they turn
> grainy -- is there a way to fix that?
>

>
Perhaps we should back up and be sure it is understood what you are 
doing in using infinitely thin surfaces in intersections and differences 
to define the whole of your object is pushing past what POV-Ray - let us 
say - robustly supports. It used to be scenes like yours would generate 
warnings along the lines that CSG operations with surface or 2D objects 
was not supported.

That said, doing what you are doing often works out OK. If the rays 
bouncing around cross the surface in a mathematically favorable way, 
things can work fine.

What I suspect in allowing some light to filter through the surface is 
we are further exposing ourselves to mathematical noise - there are now 
more rays bouncing around adding those passing through surfaces. The 
determination of inside vs outside becomes important and that is iffy / 
undefined for surfaces hanging in space.

If when you turn on the filtering of light for the ramps, are parts of 
the ramp with direct lines to the camera and light source clean, without 
graininess? I suspect yes. I doubt there is any easy fix for the
filtering and graininess. Another test would be to set the filtering to 
50% say - the graininess would get worse if coming from noise of rays 
through the surfaces.

That said. There is too a max_gradient option for parametric surfaces. I 
 >think< the default is 1.0. Your accuracy is already set really high, 
but you can crank up the max_gradient to 5.0 say and see what happens.
Calculation of the surface should be more accurate. Unfortunately, the 
render will get much slower.

Hope something said a help.

Bill P.

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