How to properly bake normal maps? I was trying to bake a normal map to give detail to a figure, and recently I got so frustrated I started working on a test file, to see if it was me doing it wrong. Sure enough, it was.

Steps I took to bake:


Create a cube.
Subdivide it flat 5 times.
Deselect all vertices and select random vertices with select >>> random and scale it out.
Repeat step 3 3-5 times.


5 Duplicate the cube and move it over.


To the second one, add a decimate modifier with unsubdivide mode on level 2. Hit Apply.
Unwrap the decimate cube with smart UV project.
Create a new image on the smart UV project. Keep the default settings and apply.
Select the first cube and then the second.
Under the bake tab in the camera panel in properties, select normals for the mode, and check selected to active. Set the margin to 0 and hit bake.


My result:
As staded by @Yvain baking one object maps to another involves projecting them on the baking faces. If you move the object away, or the faces are not pointing each other, you'll not get expected results.

 

While it would be cool not to have the object in the same place for baking highres to low, a similar behaviour would limit the user possibilities.

This is just the tip of the iceberg, as baking normal maps involves many aspects, such as resolution, uv maps, shading, cages...

I would suggest to have a look of these tutorial:


The Fundamentals of Perfect Baking (not blender related)
Blender 2.71 - Cycles Baking using Cages