What a mistake to make :

When the ratio of radius to hight is < (SMALLER !!!) +/- 500 the problem
disapears.

Wouter Depuydt schreef:
> 
> I had some strange rendering problemsw hen rendering a scene with an
> object like this :
> #declare MyObject1 = difference {
>   cylinder { <0.0,-0.07, 0.0>, <0.0, 0.07, 0.0>, 85.935 }
>   cylinder { <0.0,-1.00, 0.0>, <0.0, 1.00, 0.0>, 85.815 }
> }
> 
> It looks like someone has cut some part of the 'sides' of the cylinder.
> The endcaps are O.K., but it looks like two disks instead of a solid
> ring.
> 
> This object is used within a pretty complex CSG, but the same problem
> exists when rendering the object on its own.
> 
> When the ratio of radius to hight is > +/- 500, the problem disapears.
> I had to solve this by using a higher cylinder and cutting the ring with
> a plane :
> 
> #declare MyObject2 = difference {
>   cylinder { <0.00,-0.07, 0.00>, <0.00, 5.00, 0.00>, 85.935 }
>   cylinder { <0.00,-1.00, 0.00>, <0.00, 6.00, 0.00>, 85.815 }
>   plane { y, -0.07 }
> }
> 
> It should be seen with a little scene like this :
> 
> camera {
>   location <-0.5, 0.5, 0.5>
>   look_at <0.0, 0.0, 0.0>
> }
> 
> light_source {
>   <-5.0, 5.0, 5.0>
>   color rgb <1.0, 1.0, 1.0>
> }
> 
> object { MyObject1      //PROBLEMS !!!!!
> // object { MyObject2     //PROLBLEM SOLVED !!!!!
>   pigment { color rgb <1.0, 1.0, 0.5> }
>   transform -85.875*y
> }

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