Homogeneous volume absorption depth

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wasd
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Homogeneous volume absorption depth

Post by wasd » Thu May 17, 2018 2:44 pm

Blender 2.79b
LuxCore 2.1 alpha0
CPU Path + Metropolis (also BiDir + Metropolis and Path/BiDir + Sobol)

Glossy Translucent Material with interior homogeneous volume
I can't see any difference, though every ball have different absorption depth
From left to right: 0.01 mm, 0.1 mm, 1 mm, 1 cm, 1 m, 10 m, 100 m
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machine-le-grass-test-eg.blend
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b5.png

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B.Y.O.B.
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Re: Homogeneous volume absorption depth

Post by B.Y.O.B. » Thu May 17, 2018 3:03 pm

The transmission color of the glossy translucent mat is black, so the volume does not make any difference because no light is transmitted.
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wasd
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Re: Homogeneous volume absorption depth

Post by wasd » Thu May 17, 2018 3:52 pm

B.Y.O.B. wrote:
Thu May 17, 2018 3:03 pm
The transmission color of the glossy translucent mat is black, so the volume does not make any difference because no light is transmitted.
Do you have an example scene, which shows the difference in absorption depth? I still cannot figure out how absorption depth affects the material.
This scene has transmission color 7F7F7F at all balls.
Attachments
b6.png

kintuX
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Re: Homogeneous volume absorption depth

Post by kintuX » Thu May 17, 2018 4:40 pm

Yes, looks like it's something wrong in Blender.
Volume_trans_Abs_bug.jpg
PS.
It works fine in Material Preview, but not in Render Preview nor in Final render.
Last edited by kintuX on Thu May 17, 2018 7:02 pm, edited 1 time in total.

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B.Y.O.B.
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Re: Homogeneous volume absorption depth

Post by B.Y.O.B. » Thu May 17, 2018 5:40 pm

wasd wrote:
Thu May 17, 2018 3:52 pm
Do you have an example scene, which shows the difference in absorption depth? I still cannot figure out how absorption depth affects the material.
The absorption depth is the distance after which a white light ray (1, 1, 1) has the color that is specified as absorption color.
You can see the effect best with the null material.
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wasd
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Re: Homogeneous volume absorption depth

Post by wasd » Thu May 17, 2018 6:04 pm

B.Y.O.B. wrote:
Thu May 17, 2018 5:40 pm
wasd wrote:
Thu May 17, 2018 3:52 pm
Do you have an example scene, which shows the difference in absorption depth? I still cannot figure out how absorption depth affects the material.
The absorption depth is the distance after which a white light ray (1, 1, 1) has the color that is specified as absorption color.
You can see the effect best with the null material.
What about an example?

wasd
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Re: Homogeneous volume absorption depth

Post by wasd » Thu May 17, 2018 6:47 pm

OK. I get it. Volumes just don't really work with anything but Null material.
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Скриншот 2018-05-18 01.32.26.png
Скриншот 2018-05-18 01.32.13.png

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Re: Homogeneous volume absorption depth

Post by B.Y.O.B. » Thu May 17, 2018 7:56 pm

Volumes are independent from materials.
The material describes the surface, the volume describes everything inside or outside of the surface.

You might see something else than you expect because the material reflects too much light and transmits too little?

From left to right:
- Null
- Matte Translucent
- Glossy Translucent
- Glass
- Rough Glass

Hope this helps.
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volume_depth_example.blend
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volume_depth_example.jpg
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wasd
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Re: Homogeneous volume absorption depth

Post by wasd » Thu May 17, 2018 8:46 pm

B.Y.O.B. wrote:
Thu May 17, 2018 7:56 pm
You might see something else than you expect because the material reflects too much light and transmits too little?
Maybe.
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Скриншот 2018-05-18 03.38.55.png

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Dade
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Re: Homogeneous volume absorption depth

Post by Dade » Thu May 17, 2018 11:32 pm

wasd wrote:
Thu May 17, 2018 8:46 pm
Maybe.
You are confusing object transparency (or opacity if you prefer) with object surface+volume. Transparency makes all object (surface+volume) transparent, like with alpha channel. In your case must be set to 0, it is not what you are looking for.

The object material describes the surface (i.e. the "skin") of an object while volume describes the interior.
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