Chris Jeppesen wrote:
> 
> I like to do astronomical (space probes in the solar system) raytracing.
> Unfortunaltely, the current version of Povray can't handle extremely large
> differences in numbers which are generated by this scenario.
> 
> I wish there were a program that can simultaneously handle:
> 
> 1) Large and small. A sphere as large as the sun (10^10m) and one 1mm across

Java3D - can handle huge universes & small objects (or sets of objects)
with local coordinates based on the universal ones.


> 2) Near and Far. Simultaneously showing an object 1mm away from the camera
> and one 10^12m away.

Unless it's a really big object, all you need to do is color a single
pixel for the distant object.  On the practical side, with large
differences between foreground and background, you might be better off
building an image of the background and draping it behind the close
thing.


> 3) Small angles. Ideally, can see a 1mm object from 10^12 meters away.

At a certain point you should switch to orthogonal camera.  Not a heck
of a lot of difference between a <1 degree fov that is way off and
orthogonal.

> 
> The biggest difference in magnitude I am asking for is 10^15. Since double
> precision numbers have 16 digits of precision, there should be no problem,
> but I have tried tweaking the various constants which affect this sort of
> thing to no avail. Tweaking constants is the current limit of my skills in
> Povray source.

You will see all sorts of errors creep into your arithmetic if you
really have differences in magnitude that go right to the edge of what
can be represented by your numbers.  Each operation in a high quality
math library will only be good to within half of the bottom bit.  After
a few operations, you will see the error start to creep up to multiple
bits.

Xander

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