If I use SUComponentDefinitionToEntity, how do I add that entity to the model? Or is it just automatically an Entity in the model?
What is the difference between Entity and Entities? I see I can get the model entities and fill them, but how does an Entity work?
Entity is the base class for pretty much everything in SketchUp. But since C doesn’t support classes and inheritance we need functions like SUComponentDefinitionToEntity to cast between types. You would use SUComponentDefinitionToEntity when you need to call any of the functions in SUEntityRef.
Entities are containers for Entity objects. The model has a collection - this is the root of the model hierarchy. And each component definition has an Entities collection.
That depend on the type of Entity. Edge, Faces, Groups etc - all of them are of type Entity.
Here’s an old chart - but it shows the gist of the object hierarchy:
http://www.sketchup.com/intl/en/developer/docs/diagram.php