After a hiatus of a couple of years, I am getting back into PovRay (3.6.1
for Windows).

I've read the FAQ both in the Help File and in the Online Documentation.
There IS a clue, but not a hard answer ( " ... problems with very large
numbers when scaling ... " or something). I've also searched the newsgroup.

My main computer was destroyed in an accident, until I can afford a new one
I am using (cough...) this old Pentium 166 with 128 Mb RAM and just a
SuperVga chip for video. (I bought a cheap external serial port modem for
this thing after I lost my GOOD computer - so at least I can connect to the
Internet). This computer was originally just to run a few old legacy DOS
games. MAYBE this computer (the CPU? FPU?) has something to do with my
problem... maybe not, you never know... also I don't have a lot of time to
experiment, takes LOTS of time to render.

I am using *meters* as my basic scale, so a vector of <-3,2,-1> would be x=
-3 meters, y = 2 meters, z= -1 meter. Right now I am back to working with
old (tired?) favorites : spacecraft, space stations, planets etc. Working
with meters is great for this.

Currently I am trying to "improve" upon the "How to render a good starfield"
concept, and as an extension to that, planets, stars, nebula etc.

I am concerned with trying to render star systems as accurately *as
possible*. Naturally this means lots of BIG things that are VERY far away.
I already know that I can't accurately model, say, the sun (radius =
695,500 Km, with the scale I am working in it would be sphere { <0, 0, 0>,
695500000 } and translated to a position the approximate distance from the
earth it would be 149,600,000 or a translate using meters might be
translate <0, 0, 1.496E11> !!! These numbers are WAY too big, I know).

Since I KNOW I can't do things accurately, I need to know "How much is TOO
big and how much is TOO far?". Someone with a good knowledge of the innder
workings of PoV, say, one of the programmers might help?

Here are some clues:

When using a textured Big Sphere to make stars, if the sphere has a radius
of 10,000,000, the texture tends to *fail* below the x-z plane. When you
start to exceed 10,000,000, the star texture fails completely and all you
see is black. So far in my experiments a 9,999,999 meter Big Star Sphere
seems to be okay, but I haven't played with moving around and looking in it
yet (via changing the camera). When I get around to looking anywhere else
besides directly into the z axis, or changing the camera Y, or changing my
camera angle then 9,999,999 might fail too and I will have to "pull back".

When trying to use 3D objects instead of The Big Sphere, such as triangles,
discs, spheres, the failure distance seems to be much shorter (on the order
of thousands rather than millions). The acceptable distance for spheres
seems to be consistantly longer than for the finite patch primitives.

Other than "Just try things out until they work!", can anyone offer any
insight or *specific* useful information on this issue? Thanks. - Jeff

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