Baking Normal Maps.. baking is using high poly UV?

I’ve tried a few different times but I keep getting the same issue. I have a high poly sculpted rock with multires. I have a low poly rock based on the high poly rock. I did an auto-unwrap for the UVs. When I bake a normal map from the high poly rock to the low poly rock, the detail comes through but it’s baking it using the high poly rock’s UVs.

I’ve repeated the steps of selecting the high poly then low poly while making sure my texture map is selected and baking. It still does the same thing. Are the high and low poly UVs supposed to match up too? How would that be possible?

The high poly UV map is the auto-unwrap which comes automatically from making a cube. The low poly I did a separate auto-unwrap.

Does blender require both high poly and low poly to have the UV islands and features in the same UV space before sculpting? I feel that doesn’t make sense, especially with a retopo workflow which generates new UVs. This happens with 2.91.2 and 2.83,1

Blender should work with only the low poly UV unwrapped. Your high poly model should not matter on UV. You might look at see if the high poly has a material attached to it. You can detach the material. I have baked normal maps and the High Poly UV never matters. Except shade smooth helps. Shade smooth for both high and low poly.

I think I figured it out. It’s a bit buggy. For some reason it seems I have to select it a specific way for it to work. I was selecting the high then the low in the outliner. With the Shader Editor open, it was still defaulting to the material for the high poly object regardless of the fact I selected a second object. I was then using that node space to add an Image Texture and creating a Normal Map. I guess by default it was using the UV map associated with the high poly object simply because the material for the high poly object was open.

Now the other way… the right way…
If I select the high poly object in the Outliner, but then select the second object in the viewport, the Shader Editor updates properly to change to the low poly material, as you think it would regardless of where you select a second object. With the low poly material open in the Shader Editor, if I create an Image Texture then finish the process of baking, it uses the proper low poly UV map because it’s in the correct material.

Very odd behavior… some would say a feature.

I think this is a bug.

This might explain why I was having trouble with my normal baking the last time. I ended up deleting my retopology mesh because I thought it was in error.

Selection in outliner is inconsistent with selection in 3D view. In 3D view, you normally hit shift+click to add an object to selection and make it active. Not so in outliner. There, you have to ctrl+click for the same effect.