POV-Ray : Newsgroups : povray.general : Unwanted black spots in regular pattern : Re: Unwanted black spots in regular pattern Server Time: 27 Jun 2019 04:15:20 GMT
  Re: Unwanted black spots in regular pattern  
From: Jasper
Date: 10 May 2019 13:55:01
clipka <ano### [at] anonymousorg> wrote:
> Am 10.05.2019 um 13:22 schrieb Jasper:
>
> > I am trying to introduce photometric data files of luminaires (i.e. IESNA .ies
> > or EULUMDAT .ldt) in Povray to get "correct" lighting distributions. In order to
> > do so, I combine
> >
> > (1) a point light source
> > (2) a sphere with radius 0.01 and spherical mapping of an image map (.png with
> > the alpha channel used for transparency) which represents the lighting
> > distribution for different angles.
> >
> > My camera view is from above, simulating a satellite view (Z-direction is "up")
> > and assuming a simple planar object in xy. While the above-mentioned method
> > works in most cases, it seems that for large coordinates (e.g. 1 000 000
> > translation of both camera and luminaire in the xy plane), it no longer does (it
> > becomes a regular point source), and some black dots appear in the resulting
> > image. The strange thing is that it is not the case for translations of, e.g.,
> > 100 000.
> >
> > Has anyone encountered similar problems and/or knows the reason for this?
>
> It is generally a bad idea to place your scene far off-center. The
> reason is that POV-Ray uses floating-point mathematics, which can cover
> a wide range of values, but degrades in (absolute) precision as the
> magnitudes grow. So the further you place your objects away from the
> center, the more you invite artifacts from precision issues (think
> rounding errors).

That makes sense! Thank you


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