Cycles: Vertex Color shader node is not handled properly/ignored if no vertex color is specified (should use the 'active_render' then) #73938

New Issue

Ben Lincoln · 2020-02-17T19:28:28+01:00

Ben Lincoln commented

2020-02-17 19:28:28 +01:00

System Information
Operating system: Windows
Graphics card: AMD Radeon R9 200 series

Blender Version
Broken: 2.81a

The Vertex Color shader node is either ignored or not handled properly by the Cycles renderer. It works correctly in Eevee, and most (perhaps all) of the viewport rendering modes. In Cycles, the output of the Vertex Color node is always black. In order to have Cycles process vertex colours, it is necessary to use the old-style approach of creating an Attribute node and assigning it to the "Col" (default) attribute, or whatever the vertex colour data is named, if it is not the default.

Exact steps for others to reproduce the error
The Blender project at https://www.beneaththewaves.net/Blender_Debugging-Vertex_Colours-0001.7z (also attached to this ticket) contains a minimal reproduction of this issue. It contains two cubes which are identical except that one uses a material where the output colour is based on the Vertex Color node, and the other contains one which is based on the Attribute node set to "Col". It will appear to be correct in most (if not all) of the interactive views in Blender, as well as when rendered in Eevee. When rendered in Cycles, the cube on the left will appear 100% black. The Vertex Color output is also treated as zero in any more complex shading pipelines, when rendered in Cycles specifically.

Blender_Debugging-Vertex_Colours-0001.blend

Sample rendering in Cycles: (also available at https://www.beneaththewaves.net/Cycles_Vertex_Colours-0001.png)

**System Information** Operating system: Windows Graphics card: AMD Radeon R9 200 series **Blender Version** Broken: 2.81a The Vertex Color shader node is either ignored or not handled properly by the Cycles renderer. It works correctly in Eevee, and most (perhaps all) of the viewport rendering modes. In Cycles, the output of the Vertex Color node is always black. In order to have Cycles process vertex colours, it is necessary to use the old-style approach of creating an Attribute node and assigning it to the "Col" (default) attribute, or whatever the vertex colour data is named, if it is not the default. **Exact steps for others to reproduce the error** The Blender project at https://www.beneaththewaves.net/Blender_Debugging-Vertex_Colours-0001.7z (also attached to this ticket) contains a minimal reproduction of this issue. It contains two cubes which are identical except that one uses a material where the output colour is based on the Vertex Color node, and the other contains one which is based on the Attribute node set to "Col". It will appear to be correct in most (if not all) of the interactive views in Blender, as well as when rendered in Eevee. When rendered in Cycles, the cube on the left will appear 100% black. The Vertex Color output is also treated as zero in any more complex shading pipelines, when rendered in Cycles specifically. [Blender_Debugging-Vertex_Colours-0001.blend](https://archive.blender.org/developer/F8345528/Blender_Debugging-Vertex_Colours-0001.blend) Sample rendering in Cycles: (also available at https://www.beneaththewaves.net/Cycles_Vertex_Colours-0001.png) ![Cycles_Vertex_Colours-0001.png](https://archive.blender.org/developer/F8345529/Cycles_Vertex_Colours-0001.png)

Ben Lincoln commented

2020-02-17 19:28:28 +01:00

Added subscriber: @blincoln

blender-admin commented

2020-02-17 19:28:28 +01:00

#74459 was marked as duplicate of this issue

Philipp Oeser commented

2020-02-18 11:03:20 +01:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2020-02-18 11:03:20 +01:00

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

Philipp Oeser closed this issue

2020-02-18 11:03:20 +01:00

Philipp Oeser self-assigned this 2020-02-18 11:03:20 +01:00

Philipp Oeser commented

2020-02-18 11:03:20 +01:00

Looks like the is no vertex color layer actually selected in the node?
(you need to pick one)

Blender_Debugging-Vertex_Colours-0001-corrected.blend

Assume this is not a bug, closing.
()feel free though to comment again if issues persist or if this was a misunderstanding...

Looks like the is no vertex color layer actually selected in the node? (you need to pick one) ![image.png](https://archive.blender.org/developer/F8347175/image.png) [Blender_Debugging-Vertex_Colours-0001-corrected.blend](https://archive.blender.org/developer/F8347179/Blender_Debugging-Vertex_Colours-0001-corrected.blend) Assume this is not a bug, closing. ()feel free though to comment again if issues persist or if this was a misunderstanding...

Ben Lincoln commented

2020-02-18 14:03:47 +01:00

If I need to pick one, why does the cube on the left render as expected without doing that in every other Blender component except Cycles? The behaviour is inconsistent, and the documentation doesn't mention this. It sure seems to me that something is flagging that vertex colour layer as the default, and Cycles is ignoring it.

Viewport (Material Preview):

Viewport (Render Preview):

Eevee:

Workbench:

This is true with imported Collada models whose vertex colour layer is not named "Col" as well - everything works fine in every Blender component without explicitly selecting a vertex colour layer, except Cycles. So, again, something seems to be marking one of them as the default and using that everywhere other than Cycles.

The reason I opened this ticket is that I had a complex project which became too memory-intensive to render in Eevee any longer with a 3GB video card. It rendered perfectly in Eevee up until that time, displayed correctly in every viewport mode, but all objects were 100% black when I switched to Cycles. I spent two days troubleshooting the problem, because there was no indication in the UI as to why Cycles was behaving differently. The only reason I even began to suspect vertex colours was that if I ran Blender in debugging mode, and enabled Open Shading Language, Blender would crash when rendering the project in Cycles, and the last message in the log was:

WARNING: Shader warning [node_vertex_color]: Invalid attribute.

Respectfully, the inconsistency is a bug. Cycles should handle the Vertex Color node the same way that every other Blender component does.

If I need to pick one, why does the cube on the left render as expected without doing that in every other Blender component *except* Cycles? The behaviour is inconsistent, and the documentation doesn't mention this. It sure seems to me that something is flagging that vertex colour layer as the default, and Cycles is ignoring it. Viewport (Material Preview): ![Viewport-Material_Preview_Vertex_Colours-0001.png](https://archive.blender.org/developer/F8347447/Viewport-Material_Preview_Vertex_Colours-0001.png) Viewport (Render Preview): ![Viewport-Rendered_Vertex_Colours-0001.png](https://archive.blender.org/developer/F8347450/Viewport-Rendered_Vertex_Colours-0001.png) Eevee: ![Eevee_Vertex_Colours-0001.png](https://archive.blender.org/developer/F8347452/Eevee_Vertex_Colours-0001.png) Workbench: ![Workbench_Vertex_Colours-0001.png](https://archive.blender.org/developer/F8347454/Workbench_Vertex_Colours-0001.png) This is true with imported Collada models whose vertex colour layer is not named "Col" as well - everything works fine in every Blender component without explicitly selecting a vertex colour layer, *except* Cycles. So, again, something seems to be marking one of them as the default and using that everywhere other than Cycles. The reason I opened this ticket is that I had a complex project which became too memory-intensive to render in Eevee any longer with a 3GB video card. It rendered perfectly in Eevee up until that time, displayed correctly in every viewport mode, but all objects were 100% black when I switched to Cycles. I spent two days troubleshooting the problem, because there was no indication in the UI as to why Cycles was behaving differently. The only reason I even began to suspect vertex colours was that if I ran Blender in debugging mode, *and* enabled Open Shading Language, Blender would crash when rendering the project in Cycles, and the last message in the log was: WARNING: Shader warning [node_vertex_color]: Invalid attribute. Respectfully, the inconsistency is a bug. Cycles should handle the Vertex Color node the same way that every other Blender component does.

Philipp Oeser commented

2020-02-18 15:13:54 +01:00

Changed status from 'Archived' to: 'Confirmed'

Philipp Oeser reopened this issue

2020-02-18 15:13:54 +01:00

Philipp Oeser commented

2020-02-18 15:13:54 +01:00

Hm, if nothing is provided in the Vertex Color Node, then the active_render (Camera icon) kicks in (so watever you choose there will be rendered - in Eevee but not in Cycles)

For UVMaps this is a similar thing, if nothing is provided in the UV Map Node, then the active_render (Camera icon) kicks in (so watever you choose there will be rendered - in Eevee and for UVs also in Cycles)

So to not only keep this consistent between Cycles and Eevee, but also for Cycles being consistent to itself, will reopen as valid bug.
Suggest to use whatever is set as active_render vertex color slot if nothing is provided in the Vertex Color node...

Hm, if nothing is provided in the `Vertex Color` Node, then the `active_render` (Camera icon) kicks in (so watever you choose there will be rendered - in Eevee but not in Cycles) ![image.png](https://archive.blender.org/developer/F8347599/image.png) For UVMaps this is a similar thing, if nothing is provided in the UV Map Node, then the `active_render` (Camera icon) kicks in (so watever you choose there will be rendered - in Eevee **and for UVs also in Cycles**) So to not only keep this consistent between Cycles and Eevee, but also for Cycles being consistent to itself, will reopen as valid bug. Suggest to use whatever is set as `active_render` vertex color slot if nothing is provided in the Vertex Color node...

Philipp Oeser changed title from ~~Cycles: Vertex Color shader node is not handled properly/ignored~~ to Cycles: Vertex Color shader node is not handled properly/ignored if no vertex color is specified (should use the 'active_render' then)

2020-02-18 15:15:41 +01:00

Philipp Oeser removed their assignment 2020-02-18 15:15:41 +01:00

Ben Lincoln commented

2020-02-18 16:06:53 +01:00

Changed status from 'Confirmed' to: 'Archived'

Ben Lincoln closed this issue

2020-02-18 16:06:53 +01:00

Ben Lincoln self-assigned this 2020-02-18 16:06:53 +01:00

Ben Lincoln commented

2020-02-18 16:06:53 +01:00

Thank you.

FWIW, I think that's what the other rendering components are doing, because the Vertex Color node is basically just a convenience feature so that users don't have to add an Attribute node, figure out the name of the active vertex colour layer, and enter it in the field. If one needs to enter the name of the vertex colour layer, there's no reason (as far as I can tell) to use the Vertex Color node instead of Attribute.

Thank you. FWIW, I think that's what the other rendering components are doing, because the Vertex Color node is basically just a convenience feature so that users don't have to add an Attribute node, figure out the name of the active vertex colour layer, and enter it in the field. If one needs to enter the name of the vertex colour layer, there's no reason (as far as I can tell) to use the Vertex Color node instead of Attribute.

Ben Lincoln commented

2020-02-18 16:18:51 +01:00

...and no, I did not intend to close this task, or claim it. My user permissions are restricted enough that apparently that will happen by default if I reply to the ticket, so I won't do that again.