When using e.g. the 'smiley' CustomShape and extruding it MS-Style, the 3D representation works, but the 'eyes' and 'mouth' are pretty much invisible. They are there but not really visible.
Compared with competitor, the eyes and mouth is clearly vsisible, on both sides of the 3D-Shape (check by rotating).
This is a follow-up to tdf#118498, just a visual annoyance and should be fixed by changing the internal creation of the visual representation of CustomShapes. Currently, 'hidden' SdrObjects are created and visualized. This may be used, but for 3D, overlaying shapes would need to be depth-arranged to guarantee a visualizazion.
Even better would be to get rid of these 'hidden' SdrObjects and create primitive visualisation data immediately - but that would need bigger changes.
Created attachment 143593 [details]
PowerPoint example for comparison
PowerPoint has a different concept. It makes the extrusion from the outer outline and has contour line (violet in example) and extrusion depth and color (red in example) for this 3D-object. Then it draws the original shape like a texture on the front and on the back face with the area fill color (yellow in example) and the line color (green in example) of the original shape. PowerPoint does not take the sub-paths as separate 3D-objects. The sub-paths are missing in Wireframe mode in PowerPoint.
This is only a description for PowerPoint. I do not find in the spec how an extrusion of sub-paths has to be done in case of the enhanced-geometry of a custom-shape.
The file has objects and picture of the objects.