C3D Modeler performs all geometric calculations necessary for constructing 2D sketches and 3D models. It uses the boundary representation (B-rep) method in defining shapes and building geometric models based on 3D bodies. For composing 3D bodies, it uses surfaces and curves. It groups the resulting 3D bodies into building blocks in advance of creating more complex assemblies.
In addition to B-reps, C3D Modeler supports polygonal representations of geometric models. The kernel builds polygonal 3D models through triangulation. The overall structure is precisely the same for both boundary-representation and polygonal models, but polygonal models usually consist of approximated plate- and polygon-shaped items, and so are convenient for making calculations and generating visualizations.
As bodies and wireframes are constructed into geometric models, they generate individual build logs. The system records all of the methods employed, sequences taken and data inputted. The logs make it easier to edit the geometry later and then rebuild models with new parameters. Detailed information about objects' geometry (in the form of surfaces, curves and points) are kept in topological elements of model's objects such as faces, edges and vertices. Additional information for every object's item or object as whole can be kept inside them in the form of attributes.