Regression: color attribute is emitted as black on Eevee #104370

New Issue

Scurest · 2023-02-06T04:58:59+01:00

Scurest commented

2023-02-06 04:58:59 +01:00

System Information
Operating system: Linux-6.1.6-arch1-3-x86_64-with-glibc2.36 64 Bits
Graphics card: Mesa Intel(R) HD Graphics 4600 (HSW GT2) Intel 4.6 (Core Profile) Mesa 22.3.3

Blender Version
Broken: 3.3.2
Worked: 3.2.2

Caused by 1998269b10

Short description of error
In a specific mesh with two color attributes, and 16 materials, a Color Attribute shading node will suddenly start emitting black

Exact steps for others to reproduce the error

Open attached file or:
- Delete default Cube
- Run this script - It will create a cube with two color attributes, one red, one green. The first fifteen material slots are filled with a material that shows the red color attribute, the sixteenth, with one that shows green. Finally the faces are assigned the sixteenth slot. The cube should therefore appear green.

import bpy

def create_mat(vc):
    mat = bpy.data.materials.new(f"Mat {vc}")
    mat.use_nodes = True
    mat.node_tree.nodes.clear()
    node_vc = mat.node_tree.nodes.new('ShaderNodeVertexColor')
    node_out = mat.node_tree.nodes.new('ShaderNodeOutputMaterial')
    node_vc.layer_name = vc
    mat.node_tree.links.new(node_vc.outputs[0], node_out.inputs[0])
    return mat

bpy.ops.mesh.primitive_cube_add()
ob = bpy.context.object
ob.data.vertex_colors.new(name="Red").data.foreach_set("color", [1,0,0,1]*24)
ob.data.vertex_colors.new(name="Green").data.foreach_set("color", [0,1,0,1]*24)

mat_red = create_mat("Red")
mat_green = create_mat("Green")
for _ in range(15):
    ob.data.materials.append(mat_red)
ob.data.materials.append(mat_green)

ob.data.polygons.foreach_set('material_index', [15]*6)

Got to material preview mode,
enter edit mode (alternatively, rename the mesh or add a material slot).
The cube will suddenly become black. It remains black even if you exit edit mode.

To fix it temporarily, exit edit mode, switch to solid shading mode and view the Green color attribute in Attribute mode. Switch back to material preview mode and it will be fixed until you trigger it again.

Removing unused material slots fixes it permanently.

Other
This is an extremely weird bug. It's reduced down from a case with many more material slots, all different, and all used (so removing unused slots won't fix it). I couldn't repro without two color attributes and at least 16 material slots. Note that it depends not only the number of slots, but the exact pattern of materials in them.

eevee_attribute__bug.blend

**System Information** Operating system: Linux-6.1.6-arch1-3-x86_64-with-glibc2.36 64 Bits Graphics card: Mesa Intel(R) HD Graphics 4600 (HSW GT2) Intel 4.6 (Core Profile) Mesa 22.3.3 **Blender Version** Broken: 3.3.2 Worked: 3.2.2 Caused by 1998269b109f65373336087da7f9751a3c3317f3 **Short description of error** In a specific mesh with two color attributes, and 16 materials, a Color Attribute shading node will suddenly start emitting black **Exact steps for others to reproduce the error** - Open attached file or: - Delete default Cube - Run this script - It will create a cube with two color attributes, one red, one green. The first fifteen material slots are filled with a material that shows the red color attribute, the sixteenth, with one that shows green. Finally the faces are assigned the sixteenth slot. The cube should therefore appear green. ``` import bpy def create_mat(vc): mat = bpy.data.materials.new(f"Mat {vc}") mat.use_nodes = True mat.node_tree.nodes.clear() node_vc = mat.node_tree.nodes.new('ShaderNodeVertexColor') node_out = mat.node_tree.nodes.new('ShaderNodeOutputMaterial') node_vc.layer_name = vc mat.node_tree.links.new(node_vc.outputs[0], node_out.inputs[0]) return mat bpy.ops.mesh.primitive_cube_add() ob = bpy.context.object ob.data.vertex_colors.new(name="Red").data.foreach_set("color", [1,0,0,1]*24) ob.data.vertex_colors.new(name="Green").data.foreach_set("color", [0,1,0,1]*24) mat_red = create_mat("Red") mat_green = create_mat("Green") for _ in range(15): ob.data.materials.append(mat_red) ob.data.materials.append(mat_green) ob.data.polygons.foreach_set('material_index', [15]*6) ``` - Got to material preview mode, - enter edit mode (alternatively, rename the mesh or add a material slot). The cube will suddenly become black. It remains black even if you exit edit mode. To fix it temporarily, exit edit mode, switch to solid shading mode and view the Green color attribute in Attribute mode. Switch back to material preview mode and it will be fixed until you trigger it again. Removing unused material slots fixes it permanently. **Other** This is an extremely weird bug. It's reduced down from a case with many more material slots, all different, and all used (so removing unused slots won't fix it). I couldn't repro without two color attributes and at least 16 material slots. Note that it depends not only the number of slots, but the exact pattern of materials in them. [eevee_attribute__bug.blend](https://archive.blender.org/developer/F14255122/eevee_attribute__bug.blend)

Scurest commented

2023-02-06 04:58:59 +01:00

Added subscriber: @scurest

Scurest changed title from ~~Color Attribute Shading Node suddently turns black~~ to Color Attribute Shading Node suddently turns black when entering edit mode

2023-02-06 05:02:15 +01:00

Scurest commented

2023-02-06 06:26:10 +01:00

Narrowed it down to a having first appeared in the 3.3 release.

Germano Cavalcante changed title from ~~Color Attribute Shading Node suddently turns black when entering edit mode~~ to Regression: color attribute is emitted as black on Eevee

2023-02-07 00:15:37 +01:00

Germano Cavalcante commented

2023-02-07 00:15:37 +01:00

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