Peter Popov <pet### [at] vipbg> wrote:
: Everyone who has played with POV's radiosity knows that there's a
: tradeoff between accuracy and smoothness. Lower error_bound and you
: get splotches. Raise it, and you lose detail.

  I'm quite sure that the splotches are caused by some bug, which should be
possible to fix. However, if it is a bug, it's pretty elusive, and I don't
have the slightest idea what and where it could be.

: Basically it all comes down to tricking POV into gathering more
: samples in areas where one wants them. Since one has no direct
: per-object or per-area control over radiosity, what we need is a trick
: to introduce such controlled sampling.

  My own tests show that making the autocomputed distance_maximum smaller
makes povray calculate more samples where needed and it really increases
the quality of the lighting and reduces splotchiness. The render time
increases, of course, but the result gets better (you can actually get
rid of the splotchiness, not just change its frequency, as usually happens
when lowering error_bound).
  However, this is just a preliminary result, and I should test more. I have
yet to find a really good example where this can be clearly seen.

  Note that this does not fix the problem, but can greatly lessen its
symptoms. Lowering distance_maximum does not remove the splotchiness, just
reduces it drastically. (I have the feeling that if it really is a bug,
fixing it would get rid of the blotchiness without the need of calculating
more samples, so this would just be a workaround, not a fix.)

  Currently you can reduce the autocomputed distance_maximum only by
modifying the source code, so don't get too excited yet.

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -

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