Cycles adaptive subdivision pre-subdivides the mesh with the "hidden" render levels setting #85030

New Issue

Jesse Yurkovich · 2021-01-25T02:50:53+01:00

Jesse Yurkovich commented

2021-01-25 02:50:53 +01:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 1070 with Max-Q Design/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 451.67

Blender Version
Broken: version:

2.93.0 Alpha, branch: master, commit date: 2021-01-22 18:30, hash: aaa1d58054
2.91.0
2.90.1
Worked: n/a

Short description of error
It's not Cycles fault per se, but the mesh used for adaptive subdivision is sync'd with Cycles pre-subdivided using a "hidden" render levels setting.

This causes unnecessary runtime performance and memory problems that wouldn't otherwise be there. It is also quite unexpected from a user perspective and introduces a workflow ordering issue.

Exact steps for others to reproduce the error
adaptive-subd.blend

Add a plane
Add a sub-d modifier and set Viewport to 0 and Render to 2
Enable Adaptive Subdivision on that sub-d modifier
- The Render level of 2 is now "hidden"
Perform a render while under the debugger
- Notice that the mesh that is sync'd with cycles is already at 25 verts in the following stack (a 4 vert plane subdivided 2 times)

blender.exe!ccl::create_mesh(ccl::Scene * scene, ccl::Mesh * mesh, BL::Mesh & b_mesh, const ccl::array<ccl::Node *,16> & used_shaders, bool subdivision, bool subdivide_uvs) Line 743	C++
blender.exe!ccl::create_subd_mesh(ccl::Scene * scene, ccl::Mesh * mesh, BL::Object & b_ob, BL::Mesh & b_mesh, const ccl::array<ccl::Node *,16> & used_shaders, float dicing_rate, int max_subdivisions) Line 893	C++
blender.exe!ccl::BlenderSync::sync_mesh(BL::Depsgraph b_depsgraph, BL::Object b_ob, ccl::Mesh * mesh) Line 1045	C++
blender.exe!ccl::BlenderSync::sync_geometry::__l2::<lambda>() Line 163	C++

Disable Adaptive Subdivision on that sub-d modifier, Set Render level to 0, and Re-enable Adaptive Subdivision
Perform another render while under the debugger
- Notice that the mesh that is sync'd with cycles is correctly at 4 verts
- And the final render is much more reasonable in geometry

Setting Render levels to 0 before enabling Adaptive Subdivision:

Setting Render levels to 2 before enabling Adaptive Subdivision:

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce GTX 1070 with Max-Q Design/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 451.67 **Blender Version** Broken: version: - 2.93.0 Alpha, branch: master, commit date: 2021-01-22 18:30, hash: `aaa1d58054` - 2.91.0 - 2.90.1 Worked: n/a **Short description of error** It's not Cycles fault per se, but the mesh used for adaptive subdivision is sync'd with Cycles pre-subdivided using a "hidden" render levels setting. This causes unnecessary runtime performance and memory problems that wouldn't otherwise be there. It is also quite unexpected from a user perspective and introduces a workflow ordering issue. **Exact steps for others to reproduce the error** [adaptive-subd.blend](https://archive.blender.org/developer/F9596005/adaptive-subd.blend) - Add a plane - Add a sub-d modifier and set Viewport to 0 and Render to 2 - Enable Adaptive Subdivision on that sub-d modifier - The Render level of 2 is now "hidden" - Perform a render while under the debugger - Notice that the mesh that is sync'd with cycles is already at 25 verts in the following stack (a 4 vert plane subdivided 2 times) ``` blender.exe!ccl::create_mesh(ccl::Scene * scene, ccl::Mesh * mesh, BL::Mesh & b_mesh, const ccl::array<ccl::Node *,16> & used_shaders, bool subdivision, bool subdivide_uvs) Line 743 C++ blender.exe!ccl::create_subd_mesh(ccl::Scene * scene, ccl::Mesh * mesh, BL::Object & b_ob, BL::Mesh & b_mesh, const ccl::array<ccl::Node *,16> & used_shaders, float dicing_rate, int max_subdivisions) Line 893 C++ blender.exe!ccl::BlenderSync::sync_mesh(BL::Depsgraph b_depsgraph, BL::Object b_ob, ccl::Mesh * mesh) Line 1045 C++ blender.exe!ccl::BlenderSync::sync_geometry::__l2::<lambda>() Line 163 C++ ``` - Disable Adaptive Subdivision on that sub-d modifier, Set Render level to 0, and Re-enable Adaptive Subdivision - Perform another render while under the debugger - Notice that the mesh that is sync'd with cycles is correctly at 4 verts - And the final render is much more reasonable in geometry Setting Render levels to 0 before enabling Adaptive Subdivision: ![r0adapt.png](https://archive.blender.org/developer/F9596006/r0adapt.png) Setting Render levels to 2 before enabling Adaptive Subdivision: ![r2adapt.png](https://archive.blender.org/developer/F9596008/r2adapt.png)

Jesse Yurkovich commented

2021-01-25 02:50:53 +01:00

Added subscriber: @deadpin

Robert Guetzkow commented

2021-01-25 14:00:24 +01:00

Added subscribers: @brecht, @rjg

Robert Guetzkow commented

2021-01-25 14:00:24 +01:00

Based on this comment by @brecht on #73564 this is a known limitation.

Adaptive subdivision is not properly working yet in 2.80, and will subdivide the mesh both in Blender and Cycles. This is a known issue, one of the reasons it is still an experimental feature.

I will merge this ticket into #53901 which is the general task for the adaptive subdivision task.

Based on this comment by @brecht on #73564 this is a known limitation. > Adaptive subdivision is not properly working yet in 2.80, and will subdivide the mesh both in Blender and Cycles. This is a known issue, one of the reasons it is still an experimental feature. I will merge this ticket into #53901 which is the general task for the adaptive subdivision task.

Robert Guetzkow commented

2021-01-25 14:02:12 +01:00

Closed as duplicate of #53901

Robert Guetzkow closed this issue

2021-01-25 14:02:12 +01:00

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Cycles adaptive subdivision pre-subdivides the mesh with the "hidden" render levels setting #85030