  CSG trees are an intuitive, yet powerful technique for the representation of
geometry using a combination of Boolean set-operations and geometric
primitives. In general, there exists an infinite number of trees all describing
the same 3D solid. However, some trees are optimal regarding the number of used
operations, their shape or other attributes, like their suitability for
intuitive, human-controlled editing. In this paper, we present a systematic
comparison of newly developed and existing tree optimization methods and
propose a flexible processing pipeline with a focus on tree editability. The
pipeline uses a redundancy removal and decomposition stage for complexity
reduction and different (meta-)heuristics for remaining tree optimization. We
also introduce a new quantitative measure for CSG tree editability and show how
it can be used as a constraint in the optimization process.
