Regression: Volume Scatter bleeds across materials when there is an environment texture #101061

New Issue

Alessandro Padovani · 2022-09-14T12:38:50+02:00

Alessandro Padovani commented

2022-09-14 12:38:50 +02:00

Simplified Report

Add a loop cut in the default cube.
Assign two materials for each side. The two materials are identical and are just a volume scatter shader.
Add an environment texture, which can just be a uniform white color.
There is a dark line at the loop cut. This didn't happen in 3.2.
Remove the environment texture and replace it with a single white color.
The dark line disappears.

volumeScatterMultipleMaterials.blend

Original Report

System Information
Operating system: windows 10 21H1
Graphics card: gtx 1060 driver 472.84

Blender Version
Broken: 3.3.0
Worked: 3.2.2

Short description of error

In blender 3.3 the volume scatter shader gets color bleeding when two volume materials meet on the same geometry. This doesn't happen in blender 3.2. Test scene included scatter.blend.

Exact steps for others to reproduce the error
Based on the default startup or an attached .blend file (as simple as possible).

steps:

load the test scene scatter.blend with blender 3.2 and 3.3
render

scatter.blend

## Simplified Report - Add a loop cut in the default cube. - Assign two materials for each side. The two materials are identical and are just a volume scatter shader. - Add an environment texture, which can just be a uniform white color. - There is a dark line at the loop cut. This didn't happen in 3.2. - Remove the environment texture and replace it with a single white color. - The dark line disappears. [volumeScatterMultipleMaterials.blend](https://archive.blender.org/developer/F13491935/volumeScatterMultipleMaterials.blend) ![20220914-133127.png](https://archive.blender.org/developer/F13491937/20220914-133127.png) ## Original Report **System Information** Operating system: windows 10 21H1 Graphics card: gtx 1060 driver 472.84 **Blender Version** Broken: 3.3.0 Worked: 3.2.2 **Short description of error** In blender 3.3 the volume scatter shader gets color bleeding when two volume materials meet on the same geometry. This doesn't happen in blender 3.2. Test scene included scatter.blend. ![scatter.jpg](https://archive.blender.org/developer/F13491767/scatter.jpg) ![scatter-33.jpg](https://archive.blender.org/developer/F13491786/scatter-33.jpg) ![scatter-32.jpg](https://archive.blender.org/developer/F13491771/scatter-32.jpg) **Exact steps for others to reproduce the error** Based on the default startup or an attached .blend file (as simple as possible). steps: 1. load the test scene scatter.blend with blender 3.2 and 3.3 2. render [scatter.blend](https://archive.blender.org/developer/F13491776/scatter.blend) ![white.jpg](https://archive.blender.org/developer/F13491777/white.jpg)

Alessandro Padovani commented

2022-09-14 12:38:50 +02:00

Added subscriber: @padone

Omar Emara commented

2022-09-14 13:29:56 +02:00

Changed status from 'Needs Triage' to: 'Confirmed'

Omar Emara changed title from ~~volume scatter gets bleeding in blender 3.3, works fine in blender 3.2~~ to Regression: Volume Scatter bleeds across materials when there is an environment texture

2022-09-14 13:34:37 +02:00

Brecht Van Lommel commented

2022-09-14 14:26:38 +02:00

Added subscriber: @brecht

Brecht Van Lommel commented

2022-09-14 14:26:38 +02:00

Changed status from 'Confirmed' to: 'Archived'

Brecht Van Lommel closed this issue

2022-09-14 14:26:38 +02:00

Brecht Van Lommel commented

2022-09-14 14:26:38 +02:00

This was an intentional change to fix #100205 (Volumetrics bug).

The way materials are setup right now there's no reliable way to detect that two distinct materials should share a single volume interior. In the future there may be design changes to improve this, but for now this is not considered a bug and a single material should be used.

This was an intentional change to fix #100205 (Volumetrics bug). The way materials are setup right now there's no reliable way to detect that two distinct materials should share a single volume interior. In the future there may be design changes to improve this, but for now this is not considered a bug and a single material should be used.

Rincewind commented

2022-09-14 17:44:41 +02:00

Added subscriber: @Rincewind3D-1

Rincewind commented

2022-09-14 17:44:41 +02:00

In #101061#1417073, @brecht wrote:
This was an intentional change to fix #100205 (Volumetrics bug).

The way materials are setup right now there's no reliable way to detect that two distinct materials should share a single volume interior. In the future there may be design changes to improve this, but for now this is not considered a bug and a single material should be used.

I think it's pretty bad practice to fix a bug with a breaking change of something which worked before than claiming it's intended 👎

> In #101061#1417073, @brecht wrote: > This was an intentional change to fix #100205 (Volumetrics bug). > > The way materials are setup right now there's no reliable way to detect that two distinct materials should share a single volume interior. In the future there may be design changes to improve this, but for now this is not considered a bug and a single material should be used. I think it's pretty bad practice to fix a bug with a breaking change of something which worked before than claiming it's intended 👎

Alessandro Padovani commented

2022-09-14 18:20:22 +02:00

In #101061#1417073, @brecht wrote:
for now this is not considered a bug and a single material should be used

Please note that it is not always possible to use a single volume material for the whole object. For example if we have textures, different textures could be used for the different parts of the object, thus producing "texture seams" because of this bug. In my opinion, if this was introduced to fix #100205 then it is better to revert #100205.

Below an example where we have a texture seam because of this volumetric bug. That's where the original report comes from.

edit. p.s. And you may as well reply to #100205 that's not considered a bug and multiple objects should be used for intersecting volumes. That makes more sense than having to use a single volume material per object.

> In #101061#1417073, @brecht wrote: > for now this is not considered a bug and a single material should be used Please note that it is not always possible to use a single volume material for the whole object. For example if we have textures, different textures could be used for the different parts of the object, thus producing "texture seams" because of this bug. In my opinion, if this was introduced to fix #100205 then it is better to revert #100205. Below an example where we have a texture seam because of this volumetric bug. That's where the original report comes from. ![arcadia-33.jpg](https://archive.blender.org/developer/F13492776/arcadia-33.jpg) **edit. p.s.** And you may as well reply to #100205 that's not considered a bug and multiple objects should be used for intersecting volumes. That makes more sense than having to use a single volume material per object.

Rincewind commented

2022-09-14 19:55:40 +02:00

I totally agree with Alessasndro.
This is clearly a regression bug.

I totally agree with Alessasndro. This is clearly a regression bug.

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Regression: Volume Scatter bleeds across materials when there is an environment texture #101061

Simplified Report

Original Report