On Wed, 10 Dec 2003 13:46:08 +0200, Severi Salminen 
<sev### [at] NOT_THISsibafi> wrote:

> Here is a very small scene which shows some odd artifacts. There should 
> be no coincident surfaces here - or is there? You can see surprisingly 
> more artifacts by removing the double slash before the second box. What 
> causes these and how can I get rid of them?
>
> You can see the artifacts in the shadow of the superellipsoid.
>
>
> light_source { <0,2,2> 1}
>
> camera {
>      location <0, 0.1, -0.5 >
> }
>
> union {
>      box {<-0.25,-0.02,-0.25>,<0.25,0.0,0.25>}
>      // box {<1,1,1>,<2,2,2>}
>
>      superellipsoid { <0.4,0.4>
>                        scale <0.22,0.015,0.22>
>                        }
>      pigment{ rgb 1}
> }
>
> Severi Salminen

Looks like inaccuracy in the root solver, scaling the whole scene by 10 
removes the artifacts.
Translating the superellipsoid slightly in the y-direction solves also the 
problem.
The sturmian root solver could also help, but it can't be used (stated in 
the doc 6.5.1.11  Superquadric Ellipsoid).

-- 
light_source{20*y,1}#macro _(M,X,Y,P)#macro L(N,D)#if(N)#declare 
P=P+D;box{-
0.5,0.5translate z*mod(9*P.gray,4)pigment{rgb P}rotate 45*x+clock*y 
translate
P}L(N-1,D)#end#end#if(M)L(mod(M,8)<mod(X,3)mod(Y,3)1>-1)_(div(M,8)div(X,3)div
(Y,3)P)#end#end _(2301603551,12850,60365,20*z-5*x)plane{y,-9pigment{rgb 1}}

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