Hi,
I'm completely new to POVRAY, intention was to use it to quickly explore the
optical effects of a mirror defined using some equations. In the process of
setting things up, I find myself unable to obtain a correctly reflecting sphere
given as a parametric object. Staying close to published examples, I find that
this

camera { location <-1,3,-6> look_at <0,0,0> angle 35 }
light_source { <100,200,-200> color 1 }

// The floor
plane { <0,1,0>,-1 pigment { checker rgb <1,0,0>, rgb <1,1,0> } }

// A mirror sphere
sphere
{ <0,0,0>,1
  pigment { rgb <0,0,0> } // A perfect mirror with no color
  finish { reflection 1 } // It reflects all
}


renders a mirrored sphere with correct reflections of the checkerboard while
this

camera { location <-1,3,-6> look_at <0,0,0> angle 35 }
light_source { <100,200,-200> color 1 }

// The floor
plane { <0,1,0>,-1 pigment { checker rgb <1,0,0>, rgb <1,1,0> } }
// the sphere
parametric {
 function { sin(u)*cos(v) }
 function { sin(u)*sin(v) }
 function { cos(u) }

 <0,0>, <2*pi, pi>
 contained_by { sphere{0, 1.1} }
 accuracy 0.0001
 precompute 10 x,y,z
    pigment {
       rgb <0,0,0>
    }
    finish {
      reflection 1
    }
  }

gives a sphere, but with incorrect reflections (only a few colored
points/stripes)...

Any hints much appreciated!

Thanks,
Sven

Post a reply to this message

"sven.zenker" <sve### [at] gmailcom> wrote:
> gives a sphere, but with incorrect reflections (only a few colored
> points/stripes)...
>
> Any hints much appreciated!

Having just tested this with POV-Ray 3.6 (actually MegaPOV 1.2.1, but that
shouldn't change a thing here), I agree that this really looks bogus (well, the
comparison with a sphere shows that it definitely *is* bogus), and I'm quite
sure that this is a bug.

The good news is that POV-Ray 3.7.0.beta.32 does not seem to have it. With that
version, I found virtually no difference between the sphere and the parametric
(except for some slight jitter effects).

So you may want to try the current 3.7 beta for your experiments. POV-Ray 3.6,
at any rate, obviously isn't a reliable tool for your purposes.

Post a reply to this message

"clipka" <nomail@nomail> wrote:
> "sven.zenker" <sve### [at] gmailcom> wrote:
> > gives a sphere, but with incorrect reflections (only a few colored
> > points/stripes)...
> >
> > Any hints much appreciated!
>
> Having just tested this with POV-Ray 3.6 (actually MegaPOV 1.2.1, but that
> shouldn't change a thing here), I agree that this really looks bogus (well, the
> comparison with a sphere shows that it definitely *is* bogus), and I'm quite
> sure that this is a bug.
>
> The good news is that POV-Ray 3.7.0.beta.32 does not seem to have it. With that
> version, I found virtually no difference between the sphere and the parametric
> (except for some slight jitter effects).
>
> So you may want to try the current 3.7 beta for your experiments. POV-Ray 3.6,
> at any rate, obviously isn't a reliable tool for your purposes.

Hi clipka,
thanks for your help, so at least this issue isn't due to some misunderstanding
on my side...
I tried building the 3.7 beta on my laptop (SuSE 10.3 64bit), but wasn't able to
out of the box (using Boost 1.37 + devel packages from the Packman repos, I get
some linking errors apparently connected to either Boost threads or
libpthread). Currently have no time to look into this in detail, so this'll
have to wait till I get around to trying it on my OpenSuse 11.1 workstation,
hopefully with better luck).
Again, thanks a lot for your help!
-Sven

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