I'm experimenting with baking normal maps. In my setup I've used the default cube with some notches cut out along the edges for the high resolution object (cube-high-res), and the default cube without any changes as the low resolution target (cube-low-res1). Things were going fine, but at some point I think I must have changed something on cube-low-res1, whatever it was it started messing up the normal map result. I brought in a new default cube (cube-low-res2) as the new target and the normal map produced good results again. To find out what happened I checked everything I could between cube-low-res1 and cube-low-res2 and found no differences in them. So my question is why are the normal maps generated between then different, did something happen to cube-low-res1 that is causing the difference or is it something else?
Here is a screenshot of my 3D Viewport and object hierarchy.
The objects shown from left to right are cube-high-res, cube-low-res1 and cube-low-res2. There is also a cage object (hidden from view) which is another default cube that is scaled by 1.01 on each axis and shares an origin with cube-high-res. Now, if I in turn bring in cube-low-res1 and cube-low-res2 and bake their normal map in the Scene properties (with Cycles), I get the following two different results.
The left image is the result of baking on to cube-low-res1 which is the messed up result. The right image is the result of baking on to cube-low-res2, this result seems to be a good normal map.
To ensure alignment while doing the baking I've set the origin on cube-low-res1 and cube-low-res2 by choosing Set Origin > Origin to Geometry, I make them coincide with cube-high-res by opening the Snap Menu (shift+S) and choosing Selection to Cursor, like shown here
I've done the following checks between cube-low-res1 and cube-low-res2 to determine what can be wrong.
- Both object have the same vertices (8), edges (12) and faces (6). And they have the same dimensions (2x2x2m). I.e. they are both the default cube.
- Rotation and scale have been applied to both objects.
- I've recalculated the normals on both objects.
- I've UV unwrapped both objects in the same way. I.e. using Smart UV project with an island margin of 0.09.
- All seams have been cleared
- Both objects use the same material, and therefore also use the same Image Texture node in the Shader Editor
- The Bake settings are the same, I've set these to Bake Type: Normal, Selected to Active: checked, Cage: checked and set to cage object, Extrusion: 0.1m
The Blender version is 2.82a