LoopType

The AcBr::LoopType enum classifies a loop as interior, exterior, and so on. Peripheral loops are kLoopExterior, and there is only one such loop per face (by industry convention). Holes are returned as kLoopInterior, and there may be several per face (providing there is also an exterior loop). Cones and cylinders (whether with an elliptical or circular base) have at least two base loops (if they are complete in both u and v), which are returned as kLoopWinding as opposed to kLoopExterior due to the restriction of there being just one exterior loop (along with the fact that neither base loop is a hole). Singularities (such as the apex of a cone) are returned as kLoopUnclassified. All loops on spheric and toric surfaces, as well as closed periodic NURBS, return kLoopUnclassified.