I just did a fair amount of testing. Both with importing the obj with default settings (which separates the imported object into multiple objects based on the file’s original settings) and changing the default import settings so that it doesn’t split it into different objects.
I went back and forth trying various settings that we have discussed. The overlapping or complicated UVs seem to increase the risk of failure, but overall the baking seems a little unstable (although conditionally unstable).
Revised AO baking Material checklist:
- New blank texture file created in Blender for baking AO.
- This new file is saved as a jpeg or png externally.
- Reload this file, as it may disappear when trying to bake, causing an error.
- Material on object has a texture set to image.
Lastly, this will not prevent the baking if not done, however it may help prevent the blank AO image disappearing (I am not certain):
In the Material texture image section, assign the blank AO jpeg to it. with UV mapping and the correct UV map (I have two UV maps on the objects) that you want to bake to.
Additional AO baking OBJECT checklist:
- Object is in Edit mode.
- Select all faces.
- In the UV window, select all faces.
Now, I have found that not all of the OBJECT checklist is necessary all of the time, but with a complicated object containing mirrored UVs, all the steps should be followed.
I have also found that bakes often fail first time and you should just reload the blank AO file, or select it from the list, and hit bake again for simple bakes to work.
I have tested within the same file, on different objects and proved the following:
- On a simple object (one island) you can have all the material checklist done, but still be in Object mode (I had previously been in edit mode but not selected any of the UVs), and the bake will work.
- On a more complicated object, with multiple islands, the bake will fail in object mode. It will work in Edit mode without selecting any of the UVs.
- For an object containing overlapping mirrored UVs, it is necessary to have the faces selected in the UV window for the bake to work.
Since this seems to cover everything, the question is now: Is this conditional stability in baking a bug that should be reported to Blender devs?
Does anyone have thoughts on this? Should this checklist be altered, added to, clarified in any way?