"FexFX" <fex### [at] comcastnet> wrote:
> Thorsten Froehlich <tho### [at] trfde> wrote:
> > FexFX wrote:
> > > Are there built in limits to size and distance in povray?
> >
> > <http://tag.povray.org/povQandT/misconceptions.html#simulatingsun>
>
> Unfortunately this does not really answer my question.
> The "stars" in question are not being used as light sources...
> Are you suggesting that the problems I am having are due to these objects
> trying to recieve light from the light sources in my scene?
> Because even without light sources The scene slows to a crawl (about 1/100th
> the speed) if i try to place an object at 5 million units away from the
> camera...and then no matter how large I make it the object will not show up
> unless some edge of the object is within ~500,000 units...
> That is what I was looking for a reson for...I am perfectly fine with
> running this with the solar system not to actual scale, but stars sould be
> quadrillions of units away from the camera yet I can only place them a mere
> 500k units away before things crash to a standstill.

What is to be kept in mind is that the accuracy interval of POV for the 3D
space of your scenes is something around [1e-5 .. 1e+5], whatever you deal
with: positions (light_sources or objects), distances, sizes, and perhaps
densities, colors ...

You cannot put together a 5mm insect on a 10cm stone, on a 2000m high
mountain, on a 6378.137km earth, with a 150000000km distant sun with
10000000000000 km distant stars. The range of the size-dynamic should be
kept reasonable within those intervals, because of POV internal thresholds
and epsilons, and because of numerical accuracy.

So in order to make a planetary scene, just try POV's maximum possibilities
with a sample scene in order to make yourself an idea. Then you can place
objects where POV can handle them, and far enough for your stars to be
realistic. You could be lead to change your global scene scale from 1 pov
unit = 1 m  to 1 pov unit = 1km. It depends ... but 100k units for the sun
is not far from the max I think.

    Bruno

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