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Recently Bald Eagle has been playing with elliptical tori and he created
a parametric one. I picked it up to play with the shape - but also to
perhaps dig into why parametrics so slow.
Like many folks, initially grabbed Mike Williams's stuff and ran it -
years ago. Quickly agreed parametrics are extremely slow. I confess to
20 years plus of almost completely ignoring the things...
Well turns out the parametric's max_gradient is not like the
isosurface's max_gradient and the default of 1.0 looks to be a bad
choice. I've not run all the parametric scenes I have, but looks mostly
you want to run parametrics with gradients well below 1.0. Something
like 0.001 looks pretty good as a start. Only run into two very
complicated parametrics needing max gradients at 1.0 or above. Most, a
LOT smaller.
I've also set accuracy to 0.0005 below. The default 0.001 a little high
for today's monitors. Expect further tuning possible. I only took a
couple turns at them.
So in my mind parametric now use-ably slow, instead of never-use slow. :-)
Bill P.
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Parametric scenes from Mike Williams's site on my 2 core i3.
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povr2 <scene>.pov +a0.3 +am2 +r3 (800x600)
Param00.pov 46.082 -> 10.204 ---> -77.86% (2.7s elapsed)
Param01.pov * 411.856 -> 12.808 ---> -96.89% (3.4s elapsed)
Param02.pov 19.163 -> 16.746 ---> -12.61% (4.4s elapsed)
Param04.pov 1 515.145 -> 788.846 ---> +53.13% (198s)
param05.pov 877.672 -> 91.962 ---> -89.52% (23.6s)
param06.pov 268.503 -> 59.404 ---> -77.88% (15.2s)
param07.pov 331.665 -> 71.517 ---> -78.44% (18.2s)
param09.pov 37.754 -> 15.670 ---> -58.49% (4.1s)
param10.pov 32.087 -> 20.735 ---> -35.38% (5.4s)
param11.pov 84.101 -> 19.407 ---> -76.92% (5.1s)
param11a.pov 426.047 -> 63.336 ---> -85.13% (16.3s)
param12.pov These last all param.inc examples.
param13.pov
param14.pov
param15.pov
(*) Had artifacts at shipped settings. Not at updated. Updates running
with higher accuracy generally.
(1) See (*). Removed no_shadow modifier from both. Trying povr raw_wave
with the granite pattern and no .grey so forced to v3.8. Not apples to
apples plus color shifts. If drop back to default 0.001 accuracy better
match original (shadow tolerance issues) at 460s cpu (-10%).
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