Sketch rendering uses a Internal Engine Vectorial Hidden Line 3D view as a base for its rendering.
This means that your materials will only show if they have a vectorial fill pattern set, AND vectorial hatch lines are On in the Sketch Engine settings.
Materials that don't have a fill pattern will show as white, unless they are shadowed.
You will be able to tweak your settings to get very illusive hand-drawn-like pencil sketches.
And I might add that the Sketch Engine, which has been quite slow until now, in AC12 has got a real speed boost, and is very usable, at least if you have a machine with more than one processor core!
AC4.1-AC26SWE; MacOS13.5.1; MP5,1+MBP16,1