GPU subdivision: Last subsurf modifier is always used for GPU subdivision, even when disabled. #96283

New Issue

lumakyu · 2022-03-10T03:50:05+01:00

lumakyu commented

2022-03-10 03:50:05 +01:00

System Information
Operating system: Arch Linux (last updated Mar 10, 2022)
Graphics card: NVIDIA GeForce GTX 1070
System Info: system-info.txt

Blender Version
Broken: 3.1.0, c77597cd0e
Worked: 3.0.1

Short description of error
This bug only takes hold when GPU Subdivision is enabled.
When multiple SubSurf modifiers are added to an object, the last one in the stack determines the subdivision levels even when it is disabled.
This screenshots showcases the setup and issue:

This affects not only the viewport, but also renders:

Additionally, setting the subdivision count to 0 causes a crash (image attached is a GIF):

Exact steps for others to reproduce the error
Based on the default startup file:

Enable GPU Subdivision in Viewport -> Subdivision -> GPU Subdivision.
Add two SubSurf modifiers to the default cube.
Disable the second SubSurf modifier both in Viewport and Renders.
Change the subdivision levels on the second modifier.

I've attached an example file showcasing the issue here: gpu_subdiv_bug.blend

I understand stacking SubSurf modifiers is a little unusual. I use this often in conjunction with drivers to switch between a high-fidelity and low-fidelity SubSurf that are stacked on top of each other.

**System Information** Operating system: Arch Linux (last updated Mar 10, 2022) Graphics card: NVIDIA GeForce GTX 1070 System Info: [system-info.txt](https://archive.blender.org/developer/F12916830/system-info.txt) **Blender Version** Broken: 3.1.0, c77597cd0e15 Worked: 3.0.1 **Short description of error** This bug only takes hold when GPU Subdivision is enabled. When multiple SubSurf modifiers are added to an object, the last one in the stack determines the subdivision levels **even when it is disabled**. This screenshots showcases the setup and issue: ![gpu_subdiv_bug_setup.png](https://archive.blender.org/developer/F12916807/gpu_subdiv_bug_setup.png) This affects not only the viewport, **but also renders**: ![gpu_subdiv_bug_render.png](https://archive.blender.org/developer/F12916813/gpu_subdiv_bug_render.png) Additionally, setting the subdivision count to 0 causes a crash (image attached is a GIF): ![gpu_subdiv_bug_crash.gif](https://archive.blender.org/developer/F12916824/gpu_subdiv_bug_crash.gif) **Exact steps for others to reproduce the error** Based on the default startup file: - Enable GPU Subdivision in Viewport -> Subdivision -> GPU Subdivision. - Add two SubSurf modifiers to the default cube. - Disable the second SubSurf modifier both in Viewport and Renders. - Change the subdivision levels on the second modifier. I've attached an example file showcasing the issue here: [gpu_subdiv_bug.blend](https://archive.blender.org/developer/F12916844/gpu_subdiv_bug.blend) I understand stacking SubSurf modifiers is a little unusual. I use this often in conjunction with drivers to switch between a high-fidelity and low-fidelity SubSurf that are stacked on top of each other.

lumakyu commented

2022-03-10 03:50:05 +01:00

Added subscriber: @lumakyu

blender-admin commented

2022-03-10 03:50:05 +01:00

#97534 was marked as duplicate of this issue

blender-admin commented

2022-03-10 03:50:05 +01:00

#97361 was marked as duplicate of this issue

blender-admin commented

2022-03-10 03:50:05 +01:00

#96565 was marked as duplicate of this issue

Alaska commented

2022-03-10 08:14:54 +01:00

Added subscribers: @kevindietrich, @Alaska

Alaska commented

2022-03-10 08:14:54 +01:00

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

Alaska commented

2022-03-10 08:14:54 +01:00

I can confirm this issue, even in latest master.

CC @kevindietrich

I can confirm this issue, even in latest master. CC @kevindietrich

Raimund Klink commented

2022-03-10 14:33:53 +01:00

Added subscriber: @Raimund58

Kévin Dietrich commented

2022-04-08 13:39:36 +02:00

Added subscribers: @Ethan-Hall, @PratikPB2123, @YAFU, @iss

Kévin Dietrich changed title from ~~Wrong level count with multiple SubSurf modifiers (GPU Subdivision only)~~ to Last subsurf modifier is always used for GPU subdivision, even when disabled.

2022-04-08 13:40:21 +02:00

Philipp Oeser changed title from ~~Last subsurf modifier is always used for GPU subdivision, even when disabled.~~ to GPU subdivision: Last subsurf modifier is always used for GPU subdivision, even when disabled.

2022-04-12 16:53:07 +02:00

Philipp Oeser commented

2022-04-13 11:15:26 +02:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2022-04-13 11:15:26 +02:00

Talked to @kevindietrich , setting to High prio (since it is a bug in a new feature according to the playbook

Talked to @kevindietrich , setting to High prio (since it is a bug in a new feature according to the [playbook ](https://wiki.blender.org/wiki/Process/Bug_Reports/Triaging_Playbook)

Kévin Dietrich commented

2022-04-15 20:09:21 +02:00

Added subscribers: @Mets, @HooglyBoogly