Is there anything inherent to the way POV processes isosurfaces (and radiosity
for that matter) that would make the scale of scene objects relevant to the
results, or are any differences in scaling just a matter of floating point
rounding errors? For SSLT, it does seem that units matter, because there is the
global mm_per_unit setting to tune SSLT.
I have seen suggestions from time to time in the newsgroups about scaling up
isosurface objects if you are having difficulty cleaning up holes, or speeding
up the rendering, but again, is that because of the way isosurfaces are
processed or just the rounding errors?
In my own scenes, I have created macros to declare unit-based sizes, and never
use unit-less declarations any more. I tend to model scenes I find in the real
world, so I use the units based on my measuring device at the time, and/or known
sizes of real-world instances of those objects. I grew tired of trying to
remember whether I used metric or English measurements and doing the
conversions, so I created the macros. In addition, I set things up so I can
change the base unit used when rendering the scene. By default I work in 1cm =
1 POV unit, but if FP errors are getting in the way, I can easily change it to
meters or millimeters as needed.
-- Chris R.
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