/* I believe that I have found a bug in POV-Ray.
 *
 * I tested this several times in POV-Ray 3.1a.watcom.win32.  I am using
 * Windows 95 v4.00.950 (C build) with Internet Explorer 4 installed.
 * The actual computer I built myself, so it has no manufacturer; it is
 * running an AMD K6-II at 333MHz with 64Mb of RAM.  The only programs I
 * have running are: POV-Ray, Windows Help (with the POV-Ray docs
 * loaded), the CD Player (playing), and an MS-DOS Prompt, with nothing
 * running within.
 *
 * I have no GUI-Extensions loaded.
 *
 * This is what I have found: 
 * When the angle on the rotation below is less than (not equal to) 90,
 * the green triangle below will not be displayed.  (With d set to 1/3,
 * the three triangles should form a larger, equilateral triangle.)
 * With the rotation at 90 or greater, it works fine.  If I change the
 * union to a mesh (and move the pigments out of the triangles,
 * obviously), it works fine.  If I comment out either of the other two
 * triangles, the green triangle will be displayed.  I have checked, and
 * all three triangles' vertices are specified in the same direction.
 * (Clockwise or counterclockwise, depending where you look from.)  (Not
 * that that should have any effect, but it normally does in realtime 3D
 * renderers.)
 *
 * Please excuse the formatting on the scene.
 *
 * Note that this scene is meant to be rendered at a square aspect
 * ratio.  The bug does exhibit itself with a 4:3 aspect, however.
 */

camera { orthographic  location <0, 0, -1>  direction z  up y  right x }
light_source { <2e15, 2e15, -2e15>  color rgb <1, 1, 1> }

#declare d = 1/3;

union
{
  triangle {< d,-d,-d>,< 0,-1, 0>,< 0, 0,-1> pigment{color rgb<1,0,0>} }
  triangle {< 1, 0, 0>,< d,-d,-d>,< 0, 0,-1> pigment{color rgb<0,1,0>} }
  triangle {< 1, 0, 0>,< 0,-1, 0>,< d,-d,-d> pigment{color rgb<0,0,1>} }

  rotate 89*y

  scale .5
}

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Ben Olmstead/BEM wrote in message <36F4000C.AD914AA8@mad.scientist.com>...
>/* I believe that I have found a bug in POV-Ray.

<snip>
> * This is what I have found:
> * When the angle on the rotation below is less than (not equal to) 90,
> * the green triangle below will not be displayed.  (With d set to 1/3,
> * the three triangles should form a larger, equilateral triangle.)
> * With the rotation at 90 or greater, it works fine.  If I change the
> * union to a mesh (and move the pigments out of the triangles,
> * obviously), it works fine.  If I comment out either of the other two
> * triangles, the green triangle will be displayed.  I have checked, and
> * all three triangles' vertices are specified in the same direction.
> * (Clockwise or counterclockwise, depending where you look from.)  (Not
> * that that should have any effect, but it normally does in realtime 3D
> * renderers.)
<snip>

I seem to be able to render the green triangle fine at all rotations.  I'm
using Windows 95 POV3.1e.  Perhaps the problem is one of shading (since I
think the default is to have an ambient finish of zero?) - have you tried
using textures with an ambient value of 1, just to check this?  Or perhaps
have a bright background, so at least the shadow could be seen ?  Though I
used exactly the same shape, I did use my own camera and light definitions
(yours did not appear to show any of the shape regardless!)


Matt

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