Editing BRL-CAD Primitives
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An '''arbitrary convex polyhedron''' ('''arb''') is a geometric volume that is completely enclosed by a set of 3-dimensional planes. Each has a set of straight-edged, flat '''faces''' outlined by the intersections of those planes. The intersection of each pair of planes is a line whose intersections with other planes defines a pair of '''vertices'''. The line segment between those two vertices is an '''edge''' of the polyhedron that is shared by two faces. Each vertex is common to an equal number (at least three) of faces and edges. | An '''arbitrary convex polyhedron''' ('''arb''') is a geometric volume that is completely enclosed by a set of 3-dimensional planes. Each has a set of straight-edged, flat '''faces''' outlined by the intersections of those planes. The intersection of each pair of planes is a line whose intersections with other planes defines a pair of '''vertices'''. The line segment between those two vertices is an '''edge''' of the polyhedron that is shared by two faces. Each vertex is common to an equal number (at least three) of faces and edges. | ||
− | For example, a rectangular parallelepiped is enclosed by three | + | For example, a rectangular parallelepiped is enclosed by three orthagonal pairs of parallel planes. Their intersections define six faces, each with four edges and four vertices. There are a total of 12 edges (each shared by two faces) and 8 vertices (each shared by three faces and three edges). |
The BRL-CAD geometry file format defines two types of records for such polyhedra: | The BRL-CAD geometry file format defines two types of records for such polyhedra: | ||
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− | == | + | ==nurb== |
− | + | Non-uniform rational b-spline | |
+ | ;Handled by: none? | ||
==spline== | ==spline== | ||
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==annot== | ==annot== | ||
− | 2D | + | 2D primitive |
;Handled by: in command | ;Handled by: in command | ||
See: [[annot]] | See: [[annot]] |