The descriptions of higher order complex geometry in CAD systems are fundamentally different from and seemingly incompatible with the surface based combinatorial geometry (SBCG) format for describing the same geometry in the context of general ray-tracing applications such as radiation transport. A computer implemented process translates the high order complex geometry embodied in CAD software to the SBCG format. The translation process is comprised of a set of lower-level algorithms that operate on two data sets which are commonly available from commercial CAD software systems. The first data set is a list of trimmed surfaces which make up a given part. These data are typically available from one of the standard geometry representations such as IGES, STEP, or ACIS, at least one of which is supported by each of the major CAD systems (e.g. ProEngineer). The second data set is nodal data: an appropriately dense grouping of point coordinates, designated as either inside or outside the part. These data may be obtained by discretizing solid geometry both within and external to the part of interest using standard FE tools (e.g. ProMechanica). The process translates these two data sets into a list of analytic surfaces and a well-posed zoning statement and then optimizes that statement.
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