I have noticed that heightfields sometimes present strange bugs which I can't
explain.
  These bugs usually show up as small black areas in certain parts of the
heightfield. These areas are not shadows (no_shadow as no effect on them)
and they depend on the location of the camera (when the the heightfield is
looked from a bit different location, the size of these black areas change or
they disappear).

  Here is an example. Although you can see the bug and the effect of moving
the camera by rendering individual frames with different values of the clock
(between 0 and 1), it's best viewed as an animation (some of the black areas
slowly diminish in size and disappear). Also from the animation it's clearly
seen that they are not shadows.

----------8<----------8<----------8<----------8<----------8<----------
camera
{ location y*.03*clock
  look_at z*1
}
light_source { <90,90,0>, 1 }
height_field
{ function 900,900 { pattern { granite } }
  smooth
  scale <10,1.5,10>
  pigment { rgb 1 }
  translate -<5,.3,0>
  no_shadow
}
----------8<----------8<----------8<----------8<----------8<----------

  Any idea what causes these bugs?

  (I can create a DivX animation if necessary.)

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -

Post a reply to this message