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Path-CPU vs Path-GPU
Posted: Sat Feb 23, 2019 5:00 am
by 29A
Hi !
I'm a newbie in Lux, and wonder why is there so big difference between Path CPU and Path OpenCL rendering ?
The GPU one has a lot of reflections of the top light
- Path+CPU.png (33.42 KiB) Viewed 6439 times
- Path+GPU.png (42.03 KiB) Viewed 6439 times
Compare, Bdir
- BiDir.png (30.84 KiB) Viewed 6439 times
And with another, there are some lines appeared ???
- Path-CPU-RT.png (42.76 KiB) Viewed 6439 times
- Path-GPU-RT.png (44.16 KiB) Viewed 6439 times
I'm using Blender 2.79b, with LuxCore 2.1
On Windows 10 Pro, i5-4460S, 16Gb RAM and NVIDIA GeForce GTX 1060 3Gb
Here are the scenes
https://1drv.ms/u/s!AgbVw9eIy-h-hatVu7O6jSxKruOwoA
https://1drv.ms/u/s!AgbVw9eIy-h-hatYXeJce1UMcDuHow
The last scene won't render correctly without this displace map
https://1drv.ms/u/s!AgbVw9eIy-h-hataSTYGut0LyBVqxQ, unpack it to the same level as blend file. Blender cannot pack textures which consist of multiple files
Re: Path-CPU vs Path-GPU
Posted: Sat Feb 23, 2019 10:22 am
by Sharlybg
Try to update your Gpu driver to the last nvidia driver.
Re: Path-CPU vs Path-GPU
Posted: Sat Feb 23, 2019 3:11 pm
by 29A
You will be laughing, but after update the things got worse.
Just installed a day old (02/22/2019) NVIDIA drivers version 419.17.
Path-CPU (took 00:02:48)
- Path-CPU-new version.png (42.81 KiB) Viewed 6408 times
Path-GPU (took 00:00:35)
- Path-GPU-new version.png (49.42 KiB) Viewed 6408 times
And just to be sure, tried it on Azure VM, Windows 10 Pro, with 6 Core Xeon E5-2690, and 56Gb of RAM, NVIDIA Tesla M60, with latest GRID Drivers (412.16), you know what ? It does the same but a bit faster (00:00:30) and with the same incorrect results
- azure-tesla-M60.png (44.22 KiB) Viewed 6408 times
P.S. if anyone interested, for CPU it was 00:01:28
Re: Path-CPU vs Path-GPU
Posted: Sat Feb 23, 2019 3:41 pm
by Dade
29A wrote: ↑Sat Feb 23, 2019 5:00 am
The GPU one has a lot of reflections of the top light
Uh, I can replicated the problem on my (AMD) GPU so it is not driver related. I will check what is going on.
Re: Path-CPU vs Path-GPU
Posted: Sat Feb 23, 2019 8:21 pm
by 29A
Dade wrote: ↑Sat Feb 23, 2019 3:41 pm
29A wrote: ↑Sat Feb 23, 2019 5:00 am
The GPU one has a lot of reflections of the top light
Uh, I can replicated the problem on my (AMD) GPU so it is not driver related. I will check what is going on.
Actually both scenes are not important for me, accept it as a bug report.
Re: Path-CPU vs Path-GPU
Posted: Sun Feb 24, 2019 4:34 pm
by Sharlybg
You will be laughing
Sorry but i do
Re: Path-CPU vs Path-GPU
Posted: Mon Feb 25, 2019 9:01 am
by lacilaci
I also noticed some weird noise difference with glass material.
Looks almost as if the gpu noise/samples are smeared horizontaly.
cpu:
gpu:
Re: Path-CPU vs Path-GPU
Posted: Mon Feb 25, 2019 11:19 am
by Dade
Dade wrote: ↑Sat Feb 23, 2019 3:41 pm
Uh, I can replicated the problem on my (AMD) GPU so it is not driver related. I will check what is going on.
The problem is in the scene: there are 2 coincident "Area" and "Area.001" objects. They are 2 area lamps and "Area" has a gain set to 0.0. Just delete "Area" and CPU and GPU will produce the same rendering. Assume the duplicates are a mistake from some past editing.
Having 2 coincide objects will produce an unknown result as rays will hit one or the other based on numerical errors.
I have downloaded the second scene however you may have posted the wrong one (.blend1 extension ?), it doesn't seem to produce the rendering you posted
Re: Path-CPU vs Path-GPU
Posted: Tue Feb 26, 2019 7:39 am
by 29A
Dade wrote: ↑Mon Feb 25, 2019 11:19 am
Dade wrote: ↑Sat Feb 23, 2019 3:41 pm
Uh, I can replicated the problem on my (AMD) GPU so it is not driver related. I will check what is going on.
The problem is in the scene: there are 2 coincident "Area" and "Area.001" objects. They are 2 area lamps and "Area" has a gain set to 0.0. Just delete "Area" and CPU and GPU will produce the same rendering. Assume the duplicates are a mistake from some past editing.
Having 2 coincide objects will produce an unknown result as rays will hit one or the other based on numerical errors.
I have downloaded the second scene however you may have posted the wrong one (.blend1 extension ?), it doesn't seem to produce the rendering you posted
I see the problem with 2 areas, cannot check it right now, but i'm sure this is the reason, thank you !
2nd file is wrong, this is good one,
https://1drv.ms/u/s!AgbVw9eIy-h-hatZ024Uxkt4jR_LpQ but you also need to unzip this display map
https://1drv.ms/u/s!AgbVw9eIy-h-hataSTYGut0LyBVqxQ to the same folder. There are also 2 objects on the same place, but with animation first one (plane) is hided by scale and plane.001 is shown on 30th frame
Re: Path-CPU vs Path-GPU
Posted: Wed Feb 27, 2019 12:17 pm
by Dade
The source of the problem is in the tessellation of the cube, it is made of half million of triangles:
and the way it is done is quite terrible for numerical precision, a lot of tiny long triangles. I don't know how Blender works but you should fix the object tessellation in order to not have hundred of thousand of useless triangles (most of them can just be replaced with a single triangle). I assume you can apply some kind of object simplification modifier.
The fact that LuxCore on GPU has a reduced precision compared to LuxCore on CPU is known problem but with that kind of tessellation, you are going to have problems on CPU too, first or later.