As a layperson in the field of computer graphics, I rarely see practical applications of algorithms that take 3D geometry as the input (along with some camera and lighting parameters) and output the 2D geometry of a projection, with (self-)occlusion removed. This seems to be uncommon even for simple 3D geometry such as triangle or tetrahedral meshes, let alone for 3D spline surfaces.
At the same time, I can see demand for this: Architects, for instance, might like the ability to export SVG files from their CAD software, and scientists might prefer to have their 3D graphs as SVG files.
In contrast, algorithms that take 3D geometry as the input and output a rasterized 2D image are very common. We even have special hardware for these.
My questions are:
What are real practical applications of 3D geometry to 2D geometry projection and occlusion handling? For example, are such algorithms typically used as an intermediate step before rasterizing the projection views in CAD software?
What are obstacles? (Does the form of projections of splines become too complex? Is the occlusion handling NP-hard for spline surfaces, and hard to approximate?)