Cycles Volume Scatter Density broken in "complex" node setup #84379

New Issue

Apfel Sauce · 2021-01-04T16:55:23+01:00

Apfel Sauce commented

2021-01-04 16:55:23 +01:00

System Information
Operating system: Linux-4.12.14-lp151.28.87-default-x86_64-with-glibc2.17 64 Bits
Graphics card: GeForce GTX 1050 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 460.27.04

Blender Version
Broken: version: 2.91.0, branch: master, commit date: 2020-11-25 08:34, hash: 0f45cab862

Short description of error
When constructing this node setup, the density-slider of the second volume scatter node seems to suddenly only act in a binary way, making the volume either transparent or taking on the density-value of the other volume scatter node. The point at which this happens can be influenced by changing either the colour of the node or the factor-value of the second mix shader. The settings of the other nodes seem to have no effect on this.
Edit: After further testing, the Volume Absorbtion and first Mix Shader Nodes are not needed.

Exact steps for others to reproduce the error

*Load attached .blend
*change density of the second (marked in image) Volume Scatter node (here, the switch happens somewhere between .003 and .004)

volume_bug_simplified.blend

{F9550433, size=full}

Thanks for taking a look!

**System Information** Operating system: Linux-4.12.14-lp151.28.87-default-x86_64-with-glibc2.17 64 Bits Graphics card: GeForce GTX 1050 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 460.27.04 **Blender Version** Broken: version: 2.91.0, branch: master, commit date: 2020-11-25 08:34, hash: `0f45cab862` **Short description of error** When constructing this node setup, the density-slider of the second volume scatter node seems to suddenly only act in a binary way, making the volume either transparent or taking on the density-value of the other volume scatter node. The point at which this happens can be influenced by changing either the colour of the node or the factor-value of the second mix shader. The settings of the other nodes seem to have no effect on this. *Edit: After further testing, the Volume Absorbtion and first Mix Shader Nodes are not needed.* **Exact steps for others to reproduce the error** *Load attached .blend *change density of the second (marked in image) Volume Scatter node (here, the switch happens somewhere between .003 and .004) [volume_bug_simplified.blend](https://archive.blender.org/developer/F9550432/volume_bug_simplified.blend) {[F9550433](https://archive.blender.org/developer/F9550433/blender_volume_bug.png), size=full} Thanks for taking a look!

Apfel Sauce commented

2021-01-04 16:55:23 +01:00

Added subscriber: @apfel-sauce

Omar Emara commented

2022-02-11 15:47:44 +01:00

Added subscriber: @OmarEmaraDev

Omar Emara commented

2022-02-11 15:47:44 +01:00

Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'

Omar Emara commented

2022-02-11 15:47:44 +01:00

I can reproduce that, but unsure if this is a bug or an expected behavior. It seems to me that the high anisotropy of the top Volume Scatter node make the volume very dark, but the existence of a node with low anisotropy makes the apparent total anisotropy low, assuming a high enough density for the bottom node, which is why the density makes that difference. But the mix shader significantly favors the top node, so the probability of sampling the bottom node should be low and it should not make a significant difference.

Philipp Oeser removed the

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Cycles Volume Scatter Density broken in "complex" node setup #84379