I have a 3D lookalike graphic object made of several CAShapeLayers. All the shapes (both ceiling and walls) has to be stroked. Some of the shapes share an edge - that seems to be the root of the problem.
However it seems that the outline is being drawn around an existing outline of another shape. So I got those ugly pikes around some shapes.
How to get rid of those?
Check the lineJoin and lineCap property, Setting it to kCALineJoinRound and kCALineCapRound might help you.
https://developer.apple.com/documentation/quartzcore/cashapelayer