I just spent the last hour in Blender trying to bake a diffuse texture from a model created with photogrammetry to a lo-poly model created in Blender. I checked and double checked every setting. I went back to tutorials that I watched years ago. I looked for new issues that might be caused by the latest version. I finally found the problem.
The software I use for photogrammetry is Zephyr. It outputs the textured models in several formats. The two formats that can be imported into Blender or OBJ and FBX. I chose FBX. I chose poorly.
No matter what I did, I could not bake the texture from the FBX model to a low poly model.
When I went back to Zephyr and exported as OBJ, all my problems went away.
Exporting OBJ files with textures from Blender
This one drove me crazy. When I would post my models that I created in Blender and exported as OBJ files, people would complain that the textures weren’t included. And they were right.
I have found the solution. Before you export the file, use the “Pack All Into .blend” function. This can be found in the menu. Click File – External Data – Pack All Into .blend.
