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Unnecessary Surfaces
An unnecessary surface is an entry in a cell description that is less restrictive than another surface in the description. For example, when specifying the volume below plane 1 (x = 10) and below plane 2 (x = 0), plane 1 is unnecessary.
Unnecessary surfaces can cause a part to not be recognized as a known shape or can lead to a bad polygonalization. Because not all users write perfect input files, Moritz checks for unnecessary planes, spheres, ellipsoids, and tori. When one is found, a message is written, and the surface is not used for the polygonalization analysis. The analysis also reports some cases where the cell does not exist. The check is not made if the cell description contains special (SQ) or general (GQ) quadratic surfaces.
The combinatorial triangles algorithm may find cases where no triangles are present following the processing. If so, it writes a message suggesting the cell does not exist. One cell for which we found this occurred consisted of an RCC completely contained in an RPP with the cell description specifying the cell lie inside the RCC and outside of the RPP.
As each surface or body is intersected with the part under construction, the total number of triangles usually increases. If the intersection does not increase the number of triangles, it is likely that the current surface or body being intersected is not required in the cell description. Checking Report Unused Objects on the 3D Options property page causes a message to be written for each such surface or body. When Remove Unused Objects is checked, the noncontributing surface or body is removed from the cell description. The test may not give reliable results for cell descriptions that contain unions.
This figureshows a spherical chamber with many openings colored by cell. The descriptions for the spherical segments excluded many more of the cylindrical penetrations than those that intersect each specific cell. We loaded the model with Remove Unused Objects in effect and wrote a new MCNP input file in which many of the cell descriptions were significantly shorter. Upon loading the new file, the polygonalization time was shorter and the image was identical.
 White Rock Science http://www.whiterockscience.com/wrs.html 505 672 1105 |
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shows a spherical chamber with many
openings colored by cell. The descriptions for the spherical segments
excluded many more of the cylindrical penetrations than those that
intersect each specific cell. We loaded the model with