I know, you were all hoping this would go away quietly.  Well, I just
finally got my compiler reinstalled, so...

On Wed, 22 Apr 1998 23:14:30 GMT, par### [at] mailfwicom (Ronald L.
Parker) wrote:

>On Mon, 20 Apr 1998 16:39:01 -0400, ?
><hor### [at] popserviceohio-stateedu> wrote:
>
>>When using radiosity, POV-Ray will automatically use
>>mosaic previews during rendering to help the radiosity adapt to the
>>particulars of the scene.  
>>If you set brightness to any value other than 3.3 it will render
>>correctly during the mosaic passes, but when the scene is traced at
>>original resolution (1x1) the brightness will default back to 3.3
>
>Mosaic passes?  By default, as I said, it only does one.  If you
>specify more than one, does the brightness bug happen in the second
>pass, or only in the last (1x1) pass?  Make sure you specify a
>start/end of 8/4, or POV will second-guess you.

Despite what was later reported, what I suspected is true: the
brightness shift happens after the first pass, not before the last
pass.  Making the change I mentioned fixes the problem.

Replace the line that says

opts.Radiosity_Brightness = 3. / gather_gray;

with 

opts.Radiosity_Brightness /= gather_gray;

Interestingly enough, this "bug" is documented in rad_def.inc:

radiosity {
 count 200                // Calculate reasonable accurate samples
 error_bound 0.3          // Main quality/time adjustment = ...
 gray_threshold 0.5       // Try 0.33-0.50. Just a matter of taste
 distance_maximum 10      // Scene-dependent!  Leave 0 if unsure...
 low_error_factor 0.75
 nearest_count 7
 minimum_reuse 0.017      // reasonable number of samples in corners
 brightness 3.3   // doesn't really matter.  Not used in final output.
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 recursion_limit 1        // can be 1 (usual) or 2 (for patient...
 }

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