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Attribute node does not work in Cycles (renders black) when some reserved standard attribute names (such as "color") are used
Confirmed, NormalPublicBUG

Description

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: Radeon (TM) RX 480 Graphics ATI Technologies Inc. 4.5.14760 Core Profile Context 20.45.37.01 27.20.14537.1001

Blender Version
Broken: 2.79 - 2.93.0 Alpha, branch: master, commit date: 2021-04-14 02:19, hash: rB6776b74d0a67
Worked: Never?

Short description of error
In Cycles, the Attribute node always returns black when the attribute name is "color".
The color attribute can be a common Vertex Color or created through Geometry Nodes.

Exact steps for others to reproduce the error

  • Open attached file
  • Display render preview (note that the object is black)
  • Change the name on the node attribute and Vertex Color to "color2"

Now the node attribute works

Seems like these attribute names could be affected:
https://developer.blender.org/diffusion/B/browse/master/intern/cycles/scene/attribute.cpp$323

Event Timeline

Germano Cavalcante (mano-wii) changed the task status from Needs Triage to Confirmed.Apr 14 2021, 4:37 PM
Germano Cavalcante (mano-wii) changed the subtype of this task from "Report" to "Bug".

I just wanted to clarify that this is not limited to vertex colors. Thanks to a recently added feature, custom attributes created in geometry nodes can be used directly in Cycles without the need for vertex colors: https://developer.blender.org/rB3a6d6299d
Maybe the fix will apply to GN as well, but I think it would be good if you could modify the name or description of this task to indicate that it also affects geometry nodes, since you closed my task.

Philipp Oeser (lichtwerk) renamed this task from Attribute node does not work in Cycles when referencing a Vertex Color named "color" to Attribute node does not work in Cycles (renders black) when some reserved standard attribute names (such as "color") are used.Jan 24 2022, 12:39 PM
Philipp Oeser (lichtwerk) updated the task description. (Show Details)