POV-Ray : Newsgroups : povray.general : Artifacts when tracing somewhat high degree poly : Re: Artifacts when tracing somewhat high degree poly Server Time
22 Mar 2023 18:46:09 EDT (-0400)
  Re: Artifacts when tracing somewhat high degree poly  
From: William F Pokorny
Date: 6 Dec 2022 09:57:22
Message: <638f5852$1@news.povray.org>
On 12/6/22 04:03, Adrien wrote:
> I'm trying to use Povray to plot a surface defined by a polynomial equation
> spitted out by an auxiliary program. However, whenever the degree of that
> polynomial is 10 or more I get a bunch of artifacts/black dots. Is there a way
> to fix that ? Either directly in Povray, or in the auxiliary program ?

As per others, stronger AA in official POV-Ray is probably your best / 
quick solution.


a) The box-ish fails in your original image are very likely related to 
the shadow cache bugs (there are 2.5 of these in official releases).

b) The general spotty result is at lest somewhat related to issues with 
the official sturmiam based solver.

c) Some of the spotty result is shadow tolerance related coupled to how 
accurate the sturm solver results are.

d) The results are somewhat inaccurate simply because it's a tenth order 

Attached an image using my current povr branch where a and b already 
better due fixes.

The issue (c) can be made better with povr's shadow_tolerance keyword 
changing the default from 1e-3 to 1e-2 in this particular case. Here the 
results just are a little inaccurate due the 10th order and we pick up 
at surface roots during shadow testing as real blockage when the roots 
are inaccurate representations of the ray origin root(d)...

Attached a povr result using no AA, default shadow tolerance of 1e-3.

Bill P.

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