ID 555335 - Channel Transfer of 16k 16-bit Channel can result in only the highest resolution mipmap being generated in the resulting Paint nodes

Problem summary
Channel Transfer of 16k 16-bit Channel can result in only the highest resolution mipmap being generated in the resulting Paint nodes. This means that the resulting Channel and its Paint nodes appear to be missing textures unless the user moves the View to be very close to the Object.
The setup Support used to trigger this bug requires:

• A Channel and its Paint nodes at 16K Resolution and 16-bit Depth.
   
• Two objects with slightly different UVs, topology, and shape.
   
• A few Paint nodes connected by Merge nodes.
   
• A Channel Transfer with the default settings.

 
Customer reported version
Mari 6.0v2
 
Customer reported platform
Windows 11
 
Steps to reproduce

1. In a modelling software, create two 3D models with slightly different UVs, topology, and shape. The attached 3D models can be used.
    
2. Launch Mari.
    
3. Create a Project using ObjectA with one Channel at 16K Resolution and 16-bit Depth.
    
4. Add 3 Merge and Paint nodes. The paint nodes should also be 16K Resolution and 16-bit Depth. You should now have the following in the Node Graph:
   
   

   

   
    
5. Add ObjectB through the Objects palette.
    
6. In the Object palette, select ObjectA.
    
7. Select Channels > Transfer.
    
8. Setup a Channel Transfer of your Channel from ObjectA into ObjectB. Make sure to use the default settings in the Advanced tab.
    
9. Once the Channel Transfer is completed, select ObjectB in the Object palette.
    
10. View the newly created Channel in Object B.

 
Expected behaviour
All textures in the newly created Channel should be visible.
 
Actual behaviour
The Channel appears to be missing textures, and it displays the standard transparency checkerboard. However, if you zoom in closer to the object, the textures start to appear in a Mipmap fashion, indicating that the Channel and its Paint nodes are missing every Mipmap except for the highest resolution version.
As the textures exist, it's also possible to export them out of Mari with no issues.
 
Workaround
So that the Channel and its Paint nodes don't appear empty, the user must force Mari to recreate all Mipmaps. There are a few ways to do this, and from the following examples, the first two allow you to keep the original Node Graph:

• Select each Paint node at a time and right-click > Edit > Bake to Paint Node.
   
• In the UV View, increase the Radius of your brush so that it covers every UV, then paint every UV of every Paint node white in Multiply mode.
   
• Add a Bake Point node before the Channel node and bake it.
   
• Export and reimport the textures

 
Reproduced by support
This bug has been reproduced in:
Mari 6.0v2 - Windows 10 - CentOS 7
Mari 4.2v1 - Windows 10 - CentOS 7
 
Earliest version tested
Mari 4.2v1 - This issue appears to be in all tested versions of the product