Materials linked to 'Object' cause increased memory usage in Cycles #109978

New Issue

slowburn · 2023-07-11T18:38:50+02:00

slowburn commented

2023-07-11 18:38:50 +02:00

System Information
Operating system: Windows-11 64 Bits
Graphics card: NVIDIA GeForce RTX 3060 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 535.98

Blender Version
Broken: version: 3.6.0, branch: blender-v3.6-release, commit date: 2023-06-27 08:08, hash: c7fc78b81ecb
Worked: never?

Short description of error
If an object has a material that is linked to Object (in the material tab), then such object cannot be instanced efficiently in Cycles. Each linked copy of the object uses a large amount of memory when rendering.
In this example rendering 100 instances of Suzanne takes as much memory as 1 object, if material is linked to object's data. When material is linked to object, vram usage goes up a lot.

Exact steps for others to reproduce the error

Open the provided .blend file
Render the scene and note the memory usage
Select all monkeys
Go to material tab
While holding Alt click on the Link drop-down menu and chose Object
Render again
You should see memory usage increase significantly

**System Information** Operating system: Windows-11 64 Bits Graphics card: NVIDIA GeForce RTX 3060 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 535.98 **Blender Version** Broken: version: 3.6.0, branch: blender-v3.6-release, commit date: 2023-06-27 08:08, hash: `c7fc78b81ecb` Worked: never? **Short description of error** If an object has a material that is linked to Object (in the material tab), then such object cannot be instanced efficiently in Cycles. Each linked copy of the object uses a large amount of memory when rendering. In this example rendering 100 instances of Suzanne takes as much memory as 1 object, if material is linked to object's data. When material is linked to object, vram usage goes up a lot. ![link.jpg](/attachments/512ca3ac-e137-4e3a-ae41-5dedff02b87c) ![link2.jpg](/attachments/a2fbe6bd-6457-4fce-bcab-e397daec7e97) **Exact steps for others to reproduce the error** - Open the provided .blend file - Render the scene and note the memory usage - Select all monkeys - Go to material tab - While holding `Alt` click on the `Link` drop-down menu and chose Object - Render again - You should see memory usage increase significantly

material_linking.blend

5.2 MiB

link.jpg

315 KiB

link2.jpg

315 KiB

slowburn added the

labels 2023-07-11 18:38:50 +02:00

Pratik Borhade commented

2023-07-12 07:45:24 +02:00

Thanks for the report. Can confirm the rise in RAM/VRAM usage with cycles render engine.

Link-object option associates material with object data. Since there are 100 object and only 1 mesh data block, I thought there would be 100 material instances and that's why memory consuption increased but it's not. Material tab indicates the data-block has 100 users.

Thanks for the report. Can confirm the rise in RAM/VRAM usage with cycles render engine. Link-object option associates material with object data. Since there are 100 object and only 1 mesh data block, I thought there would be 100 material instances and that's why memory consuption increased but it's not. Material tab indicates the data-block has 100 users.

Pratik Borhade added

and removed

labels 2023-07-12 07:45:37 +02:00

Alex Fuller commented

2023-07-12 10:07:17 +02:00

Adding this here as it might be related:
https://archive.blender.org/developer/differential/0017/0017158/index.html
TLDR; Cycles assigns shaders to geometry not object so if a unique shader is applied to an instance, Cycles must duplicate memory. This patch is an attempt at addressing it.

Although reading above, it might be that there can be some logic to detect the same material being used and not have unique geometry data per-instance without the need for my patch in this case...

Adding this here as it might be related: https://archive.blender.org/developer/differential/0017/0017158/index.html TLDR; Cycles assigns shaders to geometry not object so if a unique shader is applied to an instance, Cycles must duplicate memory. This patch is an attempt at addressing it. Although reading above, it might be that there can be some logic to detect the same material being used and not have unique geometry data per-instance without the need for my patch in this case...

slowburn referenced this issue

2023-11-06 20:05:14 +01:00

Replace object-linked materials feature #99996

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Materials linked to 'Object' cause increased memory usage in Cycles #109978