I'm using Geometry Nodes to create a sort of template object, with geometry being joined together from other objects and materials assigned to the different parts.
While creating the node setup I found that joining additional geometry breaks one of my materials. This is a material that relies on the original geometry's UV data.
They way it breaks is as follows: In the joining process, somehow the UV data is interfered with, apparently causing a Factor value of 0 to be sent to the Mix node instead of a gradient of 0-1 float values.
I created a simplified example file that illustrates the problem.
Here is a GIF for comparison (before and after joining):
Above: The cube is the original object with the Geometry Nodes modifier on it. When any other mesh source is joined (in this case an Ico Sphere), the mapping of the original object breaks, turning from a purple/green gradient to solid light green.
Does anyone know why this happens and how to get around it? It seems like it might be a bug. It occurs in both Eevee and Cycles. Thanks