## Cell Polygonalization

Interactive 3D display requires that the model be described as a collection of polygons. All vertices of a polygon must be coplanar. The number of polygons depends on the complexity and shape of an object. A box, for example, can be represented by a single polygon for each of its six faces, while a sphere requires about 200 polygons for a smooth appearance.

MCNP geometry is defined in terms of cells bounded by quadric surfaces. Constructing polygonal representations from these descriptions is a complex task given the great variety of possible surfaces and their intersections. Polygonalization takes place for each cell. The cell description is analyzed to determine if the cell can be classified as one or more of a number of known

shapesfor which the code has a polygonalization algorithm. If a known shape is not found, a combinatorial triangles algorithm is used. Moritz can process and display complicated models with hundreds of cells in seconds.

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