On 5/24/19 9:48 AM, William F Pokorny wrote:
> On 5/15/19 10:04 AM, William F Pokorny wrote:
>> On 5/13/19 7:29 AM, Jasper wrote:
> ...
> 
> So, I got two issues for the price of trying to verify yours! Good news 
> is I now have a small test scene for both.
> 

I looked more closely at the test case this morning and the issues for 
me are all me... I suppose because you were lighting an x,y plane and 
moving in x,y, I coded this in my scene:

//--- scene ---
#if (0)

    //camera { Camera00    }
      camera { Camera01y   }  // An orthographic camera.
      object { LightFxtr01 }

#else
      #declare ValTranslate = 1e6;

    //camera { Camera00    translate <ValTranslate,ValTranslate,0> }
      camera { Camera01y   translate <ValTranslate,ValTranslate,0> }
      object { LightFxtr01 translate <ValTranslate,ValTranslate,0> }

#end

when the bottom part, given my scene is lighting a plane in x,z from y+, 
should have been:

    //camera { Camera00    translate <ValTranslate,0,ValTranslate> }
      camera { Camera01y   translate <ValTranslate,0,ValTranslate> }
      object { LightFxtr01 translate <ValTranslate,0,ValTranslate> }

With movement at a constant height above the plane, I get identical 
images from the origin all the way up to 1e6,0,1e6 in magnitude. I was 
curious and moved orthographic camera +y by 1e6 and it still works - in 
other words the camera to plane rays at 1e6 length are OK.

The numeric issue is moving the LightFxtr01 (point light and enclosing 
textured sphere) off the plane by 1e6. In this case there are very long 
shadow rays from the plane 'up' to the sphere and these will be 
numerically wobbly at the sphere's surface. My guess now is you might 
have done what I did in accidentally moving the light fixture away from 
the plane, but perhaps it's something else.

Instead of posting an updated image of my test case, I'll just say an 
updated one would be the left column of the previous repeated three times.

Bill P.

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