On 5/8/23 10:53, Chris R wrote:
> I realized later that I had already increased my AA thresholds for the latest
> run, to no effect. However, a combination of decreasing the max_trace_level
> from 30 to 10, as well as decreasing the block size from 32 to 8 seems to have
> markedly increased the over all speed, as well as eliminating the days-long
> rendering of the few problem blocks.
What version of POV-Ray are you using?
I'll mention a couple things I didn't note others bringing up.
1) If you have any transparency - and IIRC - since v3.7 rays transit
through transparent surfaces, with an ior of 1.0, without increasing the
max_trace count. This was done to avoid part of the old problem of black
pixels on hitting max_trace_level.
What I've had happen, very occasionally since, is some smallish number
of rays skimming a 'numerically bumpy' surface. The rays end up
transiting in an out of the shape a large number of times. Alain taught
me the trick of changing the ior to something like 1.0005 so those
transitions through transparency count again toward the max_trace_level.
2) With isosurfaces, using 'all_intersections' (really a max of 10) when
you don't need them 'all' can be expensive. I usually start with
max_trace at 2. Sometimes I cheat down to 1, if the object is simple,
opaque and I don't see artefacts.
There is too the quality level. If of the radiosity, subsurface and
media features all you use is radiosity, you can drop from 9 (=10 & =11)
to 8 and check performance without radiosity. Dropping to 7 cuts out
reflection, refraction and transparency(a). Plus, you can use start/end
row start/end column settings to render only in regions running slow for
(a) - Makes me wonder if different bucketing of some of those features
relative to the quality level would be useful given we don't today use
all the values? The internal cost of the conditionals would be similar
(the same?), I think. It would make the quality setting different than
what folks are used to using. Something to think about I guess.
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