Test scences GPU Path vs CPU BiDir

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FarbigeWelt
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Test scences GPU Path vs CPU BiDir

Post by FarbigeWelt » Sun Jul 01, 2018 3:18 pm

(EDITED: Use of attachments looks better than linked images.)

I prefer rendering with a dual GPU setup because CPU is often slower for simple scences. But what means a simple scene? It seems this means scences based on materials like matte or mirror. But as soon as glossy or metal with roughness is involved rendering gets more complex.
Cubes in Cube.zip
(75.51 KiB) Downloaded 6 times
Lenses in Cube.zip
(872.52 KiB) Downloaded 7 times
First I forgot to disable environmental light. This lead to some unexptected result.
CPU BiDir
Cube Mirror in Cube Metal default, 20 Samples CPU BiDir.jpg
Cube Mirror in Cube Metal default
GPU Path
Cube Mirror in Cube Metal default, 1000 Samples GPU Path.jpg
Cube Mirror in Cube Metal default
Setting evironmental light to none improved the rendering.
CPU BiDir
Cube Mirror in Cube Metal default, 20 Samples CPU BiDir, no env. lights.jpg
Cube Mirror in Cube Metal default
GPU Path
Cube Mirror in Cube Metal default, 1000 Samples GPU Path, no env. lights.jpg
Cube Mirror in Cube Metal default
Then I replaced point lamp with a plane, material matte, opacity 0.0, emission.
CPU BiDir
Material Light Cube Mirror in Cube Metal default, 40 Samples CPU BiDir, no env. lights.jpg
Material Light, Cube Mirror in Cube Metal default
GPU Path
Material Light Cube Mirror in Cube Metal default, 1000 Samples GPU Path, no env. lights.jpg
Material Light, Cube Mirror in Cube Metal default
Because of missing colors and orientation I've added a colorful map to the material of the outer cube.
CPU BiDir
Material Light Cube Mirror in Cube Metal mapped, 20 Samples CPU BiDir no env. lights.jpg
Cube in Cube Metal mapped
GPU Path, adaptive 0
Material Light Cube Mirror in Cube Metal mapped, 1000 Samples GPU Path, no env. lights, adaptive 0.jpg
Cube in Cube Metal mapped
Last edited by FarbigeWelt on Sat Jul 07, 2018 4:33 pm, edited 2 times in total.

FarbigeWelt
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Re: Test scences GPU Path vs CPU BiDir

Post by FarbigeWelt » Thu Jul 05, 2018 8:00 pm

6F9A2170-F055-47F7-B66F-5BFC5E1A07A2.jpeg
Stairs

FarbigeWelt
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Procedural Texture

Post by FarbigeWelt » Fri Jul 06, 2018 9:48 pm

GPU Path, 11 min.
Textured Flower.jpg
Flower

FarbigeWelt
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Strange effect using volume, CPU BiDir

Post by FarbigeWelt » Sat Jul 07, 2018 4:41 pm

Today, I tried to setup a simple scence with a glass of wine. But no matter which glass property I changed I was not confident with the result.
In the last setup I noticed a scattered beam above the glass. I miss specular reflections too. What is wrong with this scene and objects?
Glass of Wine with unexpected effect CPU BiDir 30 min.jpg
Strange beam above the glass.
Glass of Wine.zip
Blender scence
(308.41 KiB) Downloaded 6 times
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FarbigeWelt
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Re: Test scences GPU Path vs CPU BiDir

Post by FarbigeWelt » Sat Jul 07, 2018 4:49 pm

Repost pictures of lenses in cube again here. Attachment of Blender file is in first post.

CPU BiDir
Lens Glass dispersion 0.01 in Cube 20 samples CPU BiDir.jpg
Lens with dispersive Glas
3 Lenses Glass dispersion 0.01 in Cube 20 samples CPU BiDir.jpg
Different lenses with dispersive Glas
Additional picture
Objects in Cube CPU BiDir 2 h Rings Wall.jpg
Lenses in Cube with bump map walls
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B.Y.O.B.
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Re: Strange effect using volume, CPU BiDir

Post by B.Y.O.B. » Sat Jul 07, 2018 6:04 pm

FarbigeWelt wrote:
Sat Jul 07, 2018 4:41 pm
What is wrong with this scene and objects?
- some of your materials have incorrect interior/exterior volume settings (e.g. the "MatteWhite" material has no exterior volume specified, it should be set to "Air").
- This in turn makes the automatic volume detection of the camera fail. So you should either make sure that every last material in your scene has correct interior/exterior volume settings, or you have to specify the camera volume manually.
- The wine is modelled incorrectly, there is a gap between glass and wine. The wine mesh should overlap into the glass mesh, and the glass volume should be set to a higher priority than the wine volume, so it replaces the wine where the two volumes overlap.
- I would always use the Metropolis sampler with Bidir, with the only exception being that Random/Sobol are better if you are rendering with the denoiser. Without denoiser, Metropolis is the best sampler for Bidir.

by the way, the bottom of the glass looks too large to me.
In the last setup I noticed a scattered beam above the glass.
Well, you placed a spotlight above the glass? Not sure what you expected? :D

With the changes mentioned above, I get the attached result.
Attachments
scrn_2018-07-07_19-45-12.png
wrong
scrn_2018-07-07_19-45-41.png
correct (if you also raise glass volume priority)
wine.jpg
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wasd
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Re: Strange effect using volume, CPU BiDir

Post by wasd » Sat Jul 07, 2018 9:39 pm

B.Y.O.B. wrote:
Sat Jul 07, 2018 6:04 pm
FarbigeWelt wrote:
Sat Jul 07, 2018 4:41 pm
What is wrong with this scene and objects?
- some of your materials have incorrect interior/exterior volume settings (e.g. the "MatteWhite" material has no exterior volume specified, it should be set to "Air").
I have a question about volumes: shouldn't it World Volume be used when no volume is specified for the material?
And another one: when there's glass with liquid in it, both glass and liquid have air on one side and liquid/glass on the other side, what exterior volume should be used for liquid and glass?

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Re: Strange effect using volume, CPU BiDir

Post by FarbigeWelt » Sat Jul 07, 2018 9:51 pm

Hi B.Y.O.B.
Thanks for the answers and the tips.

I did not know how important setting of external and internal volume is.
The gap was intended. But good to know that overlapping is the correct solution.
Also setting priority for volumes is rather new to me.

"by the way, the bottom of the glass looks too large to me."
Maybe, but there are really a lot of shapes for wine glasses in a store with a broad sortiment.

"Metropolis sampler with Bidir"
Due to installation issues I still use version 2.0. Metropolis is default here for BiDir.

"Well, you placed a spotlight above the glass? Not sure what you expected? "
Actually I expected beam reaching top of wine but instead it disapears entering the glass. And there are not any speculars on the surface.
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Re: Test scences GPU Path vs CPU BiDir

Post by B.Y.O.B. » Sat Jul 07, 2018 10:01 pm

wasd wrote:
Sat Jul 07, 2018 9:39 pm
I have a question about volumes: shouldn't it World Volume be used when no volume is specified for the material?
Yes I would expect this too, but I am not sure LuxCore does this correctly at the moment.
The Blender addon does not handle this because I thought LuxCore would do it, but either my expectation was wrong or it's not correct in LuxCore.
I created a github issue so I don't forget it: https://github.com/LuxCoreRender/BlendL ... issues/187
wasd wrote:
Sat Jul 07, 2018 9:39 pm
when there's glass with liquid in it, both glass and liquid have air on one side and liquid/glass on the other side, what exterior volume should be used for liquid and glass?
In this case, both should use "Air" as exterior volume. The volume priority code handles the other transition cases correctly as far as I know, so on the boundary of glass and liquid the rays will be correctly refracted.
FarbigeWelt wrote:
Sat Jul 07, 2018 9:51 pm
"Well, you placed a spotlight above the glass? Not sure what you expected? "
Actually I expected beam reaching top of wine but instead it disapears entering the glass. And there are not any speculars on the surface.
Ah, this is what you meant, makes sense.
To be honest I'm not sure what's happening there, would require further investigation.
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Re:Strange effect using volume, CPU BiDir

Post by FarbigeWelt » Sat Jul 07, 2018 10:25 pm

Yes, and as you can see, beam above spot of second spot light is not visible.
It seems for me, light passing homogenous, scattering volume keeps scattering outside the volume.
Wine Glass and Spot.jpg
Beam above the wine glass
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