Data Transfer modifier not working with Vertex Groups in 4.1 Alpha #117520

New Issue

Chris Plush · 2024-01-25T20:16:44+01:00

Chris Plush commented

2024-01-25 20:16:44 +01:00

System Information
Operating system: Windows-10-10.0.19043-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3080 Ti/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 551.23

Blender Version
Broken: version: 4.1.0 Alpha, branch: main, commit date: 2024-01-23 20:10, hash: 99f9084bee58
Worked: version: 4.0.1, branch: blender-v4.0-release, commit date: 2023-11-16 16:40, hash: d0dd92834a08

Caused by 91b4f9f1f6

Short description of error
When transferring normals using the Data Transfer modifier in 4.1 Alpha, the result is broken when using vertex groups where vertices are assigned with weights between 0 and 1, like 0.5.

Exact steps for others to reproduce the error
Here is a video showing the steps to reproduce in 4.1 Alpha where it's broken, and 4.0.1 where it works -

Steps to reproduce in 4.1 Alpha:

Open the starting blend file > data_transfer_START.blend
Go into Edit Mode of the Cylinder object.
Select just the bottom edge loop (already selected in blend file).
Add a new vertex group, assign the selected vertices to this group with a weight of 1.
Select just the next edge loop above the current one, and assign these vertices to the same vertex group with a weight of 0.5.
Add a Data Transfer Modifier.
In this modifier, select the Plane as the "Source" object.
Load the vertex group into the "Vertex Group" field.
Enable the "Face Corner Data" option.
Expand the "Face Corner Data" panel and enable "Custom Normals".

The results should look like the Cylinder smoothly and seamlessly transitions into the Plane as if they're connected, but instead the resulting normals are faceted and seem flipped:

The above steps work perfectly in 4.0.1 and lesser versions, with the addition of needing to enable Auto Smooth for the Cylinder for the Data Transfer modifier to work, and increasing the Auto Smooth angle to around 65 degrees. The results are as expected:

The problem seems to occur in 4.1 Alpha only when vertices are added to the vertex group with a weight between 0 and 1. And this appears to only be a problem when normals are involved. I've tested vertex groups and different weights with other modifiers, such as the Shrinkwrap modifier for example, and the results are identical to results in 4.0.1. So maybe there's an issue with how custom normals are being handled in the latest version?

Thanks for the help!

**System Information** Operating system: Windows-10-10.0.19043-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 3080 Ti/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 551.23 **Blender Version** Broken: version: 4.1.0 Alpha, branch: main, commit date: 2024-01-23 20:10, hash: `99f9084bee58` Worked: version: 4.0.1, branch: blender-v4.0-release, commit date: 2023-11-16 16:40, hash: `d0dd92834a08` Caused by 91b4f9f1f609e1cd119dc41943cfb2c2276092ac **Short description of error** When transferring normals using the Data Transfer modifier in 4.1 Alpha, the result is broken when using vertex groups where vertices are assigned with weights between 0 and 1, like 0.5. **Exact steps for others to reproduce the error** Here is a video showing the steps to reproduce in 4.1 Alpha where it's broken, and 4.0.1 where it works - <video src="https://cgmasters.com/data_transfer_steps.mp4" controls></video> Steps to reproduce in 4.1 Alpha: 1. Open the starting blend file > [data_transfer_START.blend](/attachments/5b23f938-2228-438f-9f96-4485daa32fd9) 2. Go into Edit Mode of the Cylinder object. 3. Select just the bottom edge loop (already selected in blend file). 4. Add a new vertex group, assign the selected vertices to this group with a weight of 1. 5. Select just the next edge loop above the current one, and assign these vertices to the same vertex group with a weight of 0.5. 6. Add a Data Transfer Modifier. 7. In this modifier, select the Plane as the "Source" object. 8. Load the vertex group into the "Vertex Group" field. 9. Enable the "Face Corner Data" option. 10. Expand the "Face Corner Data" panel and enable "Custom Normals". The results should look like the Cylinder smoothly and seamlessly transitions into the Plane as if they're connected, but instead the resulting normals are faceted and seem flipped: ![4.1_Alpha_broken.jpg](/attachments/825b4d1b-38e2-4e0a-8829-5fb47c198d61) The above steps work perfectly in 4.0.1 and lesser versions, with the addition of needing to enable Auto Smooth for the Cylinder for the Data Transfer modifier to work, and increasing the Auto Smooth angle to around 65 degrees. The results are as expected: ![4.0.1_working.jpg](/attachments/c22511a1-c6a8-4c48-b397-a6918bc5cc01) The problem seems to occur in 4.1 Alpha only when vertices are added to the vertex group with a weight between 0 and 1. And this appears to only be a problem when normals are involved. I've tested vertex groups and different weights with other modifiers, such as the Shrinkwrap modifier for example, and the results are identical to results in 4.0.1. So maybe there's an issue with how custom normals are being handled in the latest version? Thanks for the help!

data_transfer_START.blend

870 KiB

4.0.1_working.jpg

126 KiB

4.1_Alpha_broken.jpg

135 KiB

Chris Plush added the