BSpline BRep Faces
Faces (patches) are the smooth connected pieces of surface of
BSpline BRep objects
The underlying surface used by a face is parametrized with two parameters (u and v). Ranges of the u,v
parameters (rectangle or parameters) are specific to each patch
A face can be closed in one (a cylinder) or both (torus) directions.
With the simple (natural) parametrization above a face is a deformed and
stretched rectangle. To model more complicated patches like triangular or
polygonal curved patches or patches with holes a face can have trimming wires (loops)
applied to the surface of the natural patch. For example, a rectangle with a hole
has two wires: The external (natural) one and internal trimming wire, defining
edge of the hole.
Properties of a patch, including parameter ranges, 3D coordinates of a point, wires, etc can be obtained via
IBRepFace_DG interface obtained IBRepShell_DG.GetFace(),
IBRepShape_DG.GetSubShapes(),
IBRepShape_DG.GetAncestors() or other methods
Sequence of edges for any wire of a face, returned by IBRepWire_DG.GetEdge() is always in Counter Clock Wise direction
relative to the positive side of the face (normal is looking into the positive, external for closed surfaces, part of 3D space). The same is true for vertices returned by IBRepWire_DG.GetVertex()
See also: Wires, Shape Explorer Sample
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