On 02/01/10 15:41, Le_Forgeron wrote:
[...]
> Your problem is that there is two kind of precision...magnitude.

Well, blast.

> So, reducing the magnitude in the scene does in fact has an impact on
> the precision. For astronomical system, you would better use thousand of
> kilometers as a unit. (Earth perimeter = 4... Radius = 4/(2*PI) )

I'd very much like to use meaningful units where possible, simply to
stop myself getting confused... at what point do the large numbers cause
problems? Could I avoid the whole issue by, for example, constructing my
model in metres or kilometres, scaling it to millions of kilometres or
AUs, and adding it to the universe? Or am I basically unable to reliably
model objects in the metre scale and objects in the 10^9 metre scale at
the same time?

[...]
> Changing to long doubles instead of double: the issue is that not only
> the type must be changed in structure (easy), but that all functions
> calls (for the maths) must be replaced with the relevant long double...

Oh, well, it was a thought. Probably wouldn't have helped much anyway.

Now, a version of Povray built to use bignums... *then* we'd be getting
somewhere!

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