2 times slower BVH construction / render time with Hair system #38771
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Reference: blender/blender#38771
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Operating system: Mac OS 10.8.5
Graphics card: AMD 5770
Blender Version
Broken: 2.69.11
4789793Worked: 2.69.0 r60991
Short description of error
To render a big Hair system on a simple mesh, the rendering time is 2 times slower compare with the build 2.69.0
On my computer it takes:
1 minute with the 2.69.0 r60991
2 minutes with the 2.69.11
4789793For info, It's worst if you select the option "Use Spatial Splits".
Exact steps for others to reproduce the error
Open my .blend file.
Clic Render and compare the render times.
HairBHVSlower.blend
Changed status to: 'Open'
Added subscriber: @EXL100
Added subscribers: @brecht, @ThomasDinges
Tested on Win 7 x64, u7-2630QM:
2.69: 2:32min
2.69.11: 2:35min
@brecht: The scene preparation is a problem(time until first tile is rendered), in 2.69 it takes about 45s, in Master 61s.
@EXL100: What CPU do you have?
On Mac OS X 10.9.1, with a Haswell i7 CPU:
2.69: 1:08min
2.69.11: 1:20min
Sync time is a problem here too: 2.69 takes 18s to do scene preparation, master 28s.
Hi,
My CPU are: 2 x Intel Xeon Nehalem Quad-core 2,93 GHz on a 2009 Mac Pro.
Many thanks for your reply.
Have a nice day.
Changed status from 'Open' to: 'Archived'
This is not a bug. This file has the Vector render pass enabled. Previously motion blur vectors for hair were not supported, but they are now, and it takes extra computation time to evaluate the hair system on the previous and next frame to compute them.
Ok good to know. Thanks!
But, without any extra passes, just the "Combined" active, my render time are:
2.69: 46 sec
2.69.11: 1minute 24
No Motion blur, no extra passes.
Are you sure that's accurate? It renders slight faster in 2.69.11 here on OS X. Where is the extra render time coming from, is it in synchronizing, BVH building, or rendering itself?
I did a new test (3 times):
2.69: Synchro 10 secondes; BVH 17 secondes Render 20 secondes; total 47 secondes
2.29.11: Synchro 15 secondes; BHV 50 secondes; Render 20 secondes; total 1minute 25sec
Hair_BHVSlower2.blend
Changed status from 'Archived' to: 'Open'
Ok, that's quite strange as the BVH building code didn't really change since 2.69.
From the revision hash I guess it's the 2.70 test build that you are using, not the one from builder.blender.org. I tested them both but didn't find the 2.70 test build to be slower than the one from builder.blender.org or the 2.69 release.
I'm not sure what might be causing this then. If it was the SSE/AVX optimizations then that would affect only the path tracing time but not the BVH build.
Ok thanks for this info.
New test:
Blender 2.69 hash
e72775eSynchro 15 secondes
BVH 15 secondes
Render 20 secondes
Total 50 secondes
Better ;)
Changed status from 'Open' to: 'Resolved'
Ok, I think this was broken/fixed then after OS X build system tweaking that happened in recent days, the final 2.70 release performance should be ok again. The few extra seconds in synchronization can be explained by more code that was added there to avoid some render issues.
Added subscriber: @jaalto-3
Thanks for the hair vector blur fix, Brecht.