Regression: Cycles point density node with a vertex color source renders without vertex colors (if these come from a Store Named Attribute node)) #114872

New Issue

Ryan Guy · 2023-11-14T22:59:37+01:00

Ryan Guy commented

2023-11-14 22:59:37 +01:00

System Information
Operating system: Windows-10-10.0.22621-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 4090/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 536.99

Blender Version
Broken: version: 4.0.0, branch: blender-v4.0-release, commit date: 2023-11-13 17:26, hash: 878f71061b8e
Worked: version: 3.1.2, branch: master, commit date: 2022-03-31 17:40, hash: rBcc66d1020c3b

Short description of error

When using a Cycles Point Density node with the color source set to a vertex color attribute, the render results in all black points instead of using the vertex colors. This renders correctly in Blender 3.1 and seems to be broken in Blender 3.2 or later.

This is the correct render result in Blender 3.1 (top right editor):

This is the incorrect render result when opened in Blender 4.0:

I have tested recreating the setup in a new Blender 4.0 file and am able to reproduce the issue.

Exact steps for others to reproduce the error

Blend file created in Blender 3.1: vertex_color_source_example.blend

Open Blend file
Set viewport to rendered mode

Result: The point density colors are all black in Blender 3.2 or later.

**System Information** Operating system: Windows-10-10.0.22621-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 4090/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 536.99 **Blender Version** Broken: version: 4.0.0, branch: blender-v4.0-release, commit date: 2023-11-13 17:26, hash: `878f71061b8e` Worked: version: 3.1.2, branch: master, commit date: 2022-03-31 17:40, hash: `rBcc66d1020c3b` **Short description of error** When using a Cycles Point Density node with the color source set to a vertex color attribute, the render results in all black points instead of using the vertex colors. This renders correctly in Blender 3.1 and seems to be broken in Blender 3.2 or later. This is the correct render result in Blender 3.1 (top right editor): ![point_density_blender_3.1.jpg](/attachments/6e2b3e68-6a8f-4b5f-80b1-107a153d0bd0) This is the incorrect render result when opened in Blender 4.0: ![point_density_blender_4.0.jpg](/attachments/4177c074-7ab6-4f7e-9dca-b132b3254377) I have tested recreating the setup in a new Blender 4.0 file and am able to reproduce the issue. **Exact steps for others to reproduce the error** Blend file created in Blender 3.1: [vertex_color_source_example.blend](/attachments/f9622fe4-9f97-4e82-ad09-5ea9d6f3dd13) 1. Open Blend file 2. Set viewport to rendered mode Result: The point density colors are all black in Blender 3.2 or later.

point_density_blender_4.0.jpg

327 KiB

vertex_color_source_example.blend

880 KiB

point_density_blender_3.1.jpg

342 KiB

Ryan Guy added the

labels 2023-11-14 22:59:38 +01:00

Philipp Oeser commented

2023-11-15 09:18:08 +01:00

Can confirm, will check

Philipp Oeser added

and removed

labels 2023-11-15 09:18:57 +01:00

Philipp Oeser commented

2023-11-15 13:34:36 +01:00

Pretty sure this broke with b9799dfb8a

pointdensity_cache_vertex_color relies on byte colors, after b9799dfb8a these are now float colors when written to by the Store Named Attribute node.

CC @JacquesLucke

I found this:
#98803 (comment)

behavior of the geometry nodes modifier changed a little bit. Previously, it would write the new attribute values into the existing byte-color attribute (because it was presented to geometry nodes as a float-color attribute internally). Now, the modifier deletes the byte-color attribute and creates a float-color attribute with the same name.

When debugging, I found the same (the attribute is now CD_PROP_COLOR instead of CD_PROP_BYTE_COLOR after the Store Named Attribute node . I dont really get the commit message from b9799dfb8a, which says

Support writing to byte color attributes in Store Named Attribute node.

How is this done?

This was also mentioned here #98803 (comment)

You can try using the Store Named Attribute node to manually create the Byte-Color Face-Corner attribute, I had some limited success with that. Maybe try to avoid overwriting an existing attribute and just create a new one instead.

How would I do that? The only option I see is Color (no Byte Color)

Pretty sure this broke with b9799dfb8a78dddbb3591dcb3e0b4de954c80fee `pointdensity_cache_vertex_color` relies on byte colors, after b9799dfb8a78dddbb3591dcb3e0b4de954c80fee these are now float colors when written to by the `Store Named Attribute` node. CC @JacquesLucke I found this: https://projects.blender.org/blender/blender/issues/98803#issuecomment-124058 > behavior of the geometry nodes modifier changed a little bit. Previously, it would write the new attribute values into the existing byte-color attribute (because it was presented to geometry nodes as a float-color attribute internally). Now, the modifier deletes the byte-color attribute and creates a float-color attribute with the same name. When debugging, I found the same (the attribute is now `CD_PROP_COLOR` instead of `CD_PROP_BYTE_COLOR` after the `Store Named Attribute` node . I dont really get the commit message from b9799dfb8a78dddbb3591dcb3e0b4de954c80fee, which says > * Support writing to byte color attributes in `Store Named Attribute` node. How is this done? This was also mentioned here https://projects.blender.org/blender/blender/issues/98803#issuecomment-124058 > You can try using the Store Named Attribute node to manually create the Byte-Color Face-Corner attribute, I had some limited success with that. Maybe try to avoid overwriting an existing attribute and just create a new one instead. How would I do that? The only option I see is `Color` (no `Byte Color`)

Philipp Oeser added

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Regression: Cycles point density node with a vertex color source renders without vertex colors (if these come from a Store Named Attribute node)) #114872