I will try to explain the algorithm. I hope it will be comprehensible. If not, tell me and I will explain it more deeply.

What elements to use?

SL Primitives are geometric primitives like cubes, spheres and cylinders. To find them in a mesh you need to specify them independent from size, rotation and position. Therefore I define topologies to describe the primitives. A topology consists of elements and neighbourhood relations between elements. For expample: you have an edge and it is connected to another edge orthogonally. To optimize the SL Primitive count I will not use edges but introduce “pieces” which are the smallest units in a topology but may contain several edges. Other elements are curves and faces. With those elements you are able to define the abstract primitives.

How to find those topologies in a mesh?

First the program will retrieve all edges from the Sketchup Model. It will take every edge, try to expand it and search on its basis for possible topologies. To expand means that the program will look if the edge matches a piece, and if there are other edges which elongate it. The piece and its neighbours are the starting condition for the topologies. If they match the topologies, they will be saved in a dynamic list with the piece, the state and the topology. The state defines the completion of a to-be-completed-topology. Afterwards every item of the dynamic list will be further processed step by step until the topology cant be further processed, or the topology is being completed.

The Description is simplified, but those are the main ideas.