The Persistence of Vision Raytracer (POV-Ray).

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Attached to Project: POV-Ray
Opened by Christoph Lipka - 2009-09-18
Last edited by William F Pokorny - 2016-10-29

FS#60 - Artifacts using prism in CSG

Using prisms in intersecion or difference CSG objects may cause artifacts in POV-Ray 3.6.2 as well as 3.7.0.beta.34, as demonstrated by the following code:

camera {
  right    -x
  up        y*image_height/image_width
  location  <-24,19,12>
  look_at   <0,0,0>

light_source { <100,200,100> color rgb 1 }

plane { y, -2 pigment { color rgb 1 } }

#declare KeyValue = 1.366; // pick any you like

difference {
  prism {
    linear_sweep -0.5,0.5, 4
  intersection {
    cylinder { <-7,-0.51,1>, <-7, 0.51,1>, 4.0 }
    plane { z, KeyValue }
  pigment { color rgb 0.5 } 

Apparently the surface of the other object becomes visible when it exactly coincides with a vertex of the prism; probably there is a failure of the inside() test for such values.

Christoph Lipka commented on Thursday, 25 August 2011, 19:09 GMT

I had hoped someone else might pick up this glove. But as it is a pretty old bug (I’d guess it has been around ever since), I see no need to rush it into the .0 release of 3.7 and risk breaking the prism inside() test for other special cases.

William F Pokorny commented on Saturday, 29 October 2016, 12:53 GMT

Now tracked on github as issue #139.


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