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Cells
Cells are regions of space bounded by surfaces. Cells can be defined interactively or by typing a cell description on the Cell property sheet. Material, importance, and universe assignments are made either interactively or on the property sheet. Visual attributes, such as color and whether the draw as solid or wireframe in 3D can be set on the property sheet or with the 2D and 3D context menus. A separate style is applied to pick ed cells. Cell picking is enabled by selecting Pick in the Cell menu. Holding the Control key permits picking of multiple cells. The context menus contain commands for selecting indivdual cells or all cells with the picked material. The Selection dialog permits selection of cells by cell number, material, density, and universe; various operations can be made on the selected cells from the dialog. Cells or groups of cells can be translated and duplicated (see the previous page). Fill assignments are made on the property sheet. An ignore style, which is set by mate rial, prevents polygonalization and 3D display; ignored cells are still shown in the 2D plots.
Cells are defined from combinations of surfaces and/or solid bodies. If a pure solid body geometry is desired, such as for ACCEPT, it may be convenient in some cases to define the geometry at first in terms of surfaces and then convert the model to solid body geometry.
The combination of surfaces and bodies defining a cell is known as the cell description. In addition to surfaces and bodies, the description can contain parentheses, union operators, and complements. A description containing any of the latter three operators is a complicated description. Reasons for avoiding excessively complication descriptions are discussed here.
Moritz defines a bounding box for each cell that is a rectangular region completely enclosing the cell. The bounding box is used to speed up algorithms that find the cell containing a point. In some cases, such as when an alternate cell description is used, the bounding box may be inaccurate. The BBox command can be used to enter the correct bounding box for a cell and/or prevent evaluation of the box from the cell’s 3D polygons.
 White Rock Science http://www.whiterockscience.com/wrs.html 505 672 1105 |
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