Open Scad is an open source program for rendering 3d models. The input of the geometry data is not done interactively here, but by a textual programming language. So a generator for Oscad is simply a program text generator.
The 3d data is created from Primitives
Lines
Circles
Spheres
Cylinders and cones
Polygons.
There are also the normal Transformations and modifications:
affine mappings
Extrusions
boolean combinations.
Curved lines/surfaces (i.e. NURBS objects) must be composed of polygons. OSCAD cannot do that itself, it has to be programmed.
Colors are only supported in a roundabout way (only in preview mode).
The Performance is not particularly good. Unfortunately, it cannot be improved by parallelization or a modern graphics card either. A large part of the processing runs on only one processor. For slightly larger models, loading takes in the minute range (depending on the number of polygons).