On Tue, 02 Apr 2002 15:32:03 +0200, "Thorsten Froehlich" <tho### [at] trfde>
wrote:
> > >* Shadow rendering problem
> >
> > At first I think originall report needs some changes. First instead
> > multiplying coordinates of camera probably scale sc should be applied at end.
> > Second light_source should be also scaled with sc to recreate the same exact
> > world. Anyway I think it is EPSILON problem.
>
> So you are suggesting it is only an odd camera and light position together
> with an overall very "small" scene?

I suggest that after intersection test for 'screen ray' interesection test for
'shadow ray' returns point so close to original intersection point that distance
between them is lower than some epsilon and therefore is considered as the same
surface and not produce shadow.

> Does it go away when scaling everything
> by 10 or 100?

Yes I tested, It appear only for small values, not for large.
Try below animation with +KFF20

#declare sc=10^div(frame_number-9,2);

#if(mod(frame_number-1,2)=0)
  merge {
#else
  union {
#end
box{<-.5,0.8,-.5>,<.5,1.2,.5> pigment{rgb 1} scale sc }
box{<-.5,0,-.5>,<.5,.4,.5> pigment{rgb 1} scale sc }
box{<-.5,0,-20>,<20,-.2,20> pigment{rgb 1} scale sc }
}

background{rgb<1,0,0>}

light_source{<-200,150,100> rgb 1 scale sc}

camera{
  location<2,3,-4>
  look_at<-200,-400,1000>
  scale sc
}

ABX

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