Add Backface Culling option to Map Object
Description of the feature
Currently, when you use the Map Object tool (Filters -> Map -> Map Object...) to map a transparent image onto, say, a sphere, you see the backfaces (the half of the sphere pointing away from the view) of the sphere due to the transparency of the rest of the image. This may be undesirable.
It would be nice if there was an option to disable rendering of the backfaces (or even render the backfaces onto a seperate layer). Currently, if you want to achieve this effect, you have to delete the parts of the image that corresponds to the projected area of the backside of the sphere, but this is quite difficult for an arbitrary orientation.
Current behaviour of Map Object gives this result: Image to be mapped:
Desired result with backface culling enabled:
Use cases
This is useful when creating planets where you want to apply different material settings (in the Map Object menu) to different parts of the globe. For example, with backface culling, you could project the map of the ocean with one level of reflection and then project the map of the land with a weaker level of reflection. Currently the two resulting projections are very hard to combine, because the backface of the projected water ends up on top of the projected land.