screwtop nous apporta ses lumieres en ce 06/03/2006 19:31:
> I'm trying to construct some space scenery containing a few very large
> objects (Sun, Earth, Moon), and a small number of space vessels (~200 m in
> length).  I started out using a scale of 1 unit = 1 m, but found that large
> objects in the scene disappeared - they simply weren't being rendered.  I
> switched to 1 unit = 1e6 m, which I thought might be a good compromise,
> which is better, but the image is very grainy when both large and small
> objects are rendered in the same scene.  I think these effects must be due
> to limits of floating-point precision (this is POV-Ray 3.6 on 32-bit
> Windows XP).  Is there any kind of workaround for this?  I'd really like to
> work to scale if possible.
> 
> Is the 64-bit version of POV-Ray likely to work better for this kind of
> scenery? I am using an AMD64 system but currently have no 64-bit Windows
> installation; IIRC, SSE/SSE2 has 128-bit FP registers.
> 
> Thanks in advance!
> 
> 
> 
> 
Look at the other replys first.
As for your CPU, 32 bits and 64 bits both have 64 bits FPU. In fact, even the latest
16 bits CPU, 
those with integrated FPU, where equiped with 64 bits FPU. 64 bits is the size
required for double 
presision floating point operations.
If you have the source code, you can change the epsilon value and compile it, but be
carefull not to 
overdo it. As the values get smaler, you can get very close to the resolution limit
imposed by the 
double presision operations. This, in turn, will lead to more rounding and
granulausity errors, 
causing "random" artefacts.

-- 
Alain
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