To illustrate the effectiveness of my new addition, I did some sample
renders using an HDRI that had a full dynamic range.

The 1st column shows scenes rendered with the original, full range HDRI,
strong shadows from the sun are noticeable and prevalent.

The 2nd column shows the same scenes with a clipped version of the original
HDRI, the scene lighting can be seen to be more uniform due to the clipping
of the suns brightness, and the hard shadows are lost.

The 3rd column shows the scenes using the clipped version of the HDRI, but
with the clipped areas 'rebuilt'.  The shadows from the sun can be seen to
return.  The result is very similar to the original, but close
investigation shows slight differences due to the estimation process and
information that was lost from the clipping that cannot be recovered (eg,
clipping effectively makes the clipped clours white, losing any colour
information and the rate of brightness increase across the clipped area).

Also, the true maximum brightness in the clipped area can only be assumed
and the parameters tweaked until the result looks 'right'.  In this test
the orignal was able to serve as a reference, and used to achieve a
convincing effect.

-tgq

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