mirror of https://github.com/CGAL/cgal
Tweak wording in the manuals for the 3D Polyhedral Surface pkg
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@ -11,14 +11,14 @@ namespace CGAL {
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\image latex halfedge.png
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Vertices represent points in 3d-space. Edges are straight line segments
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between two endpoints. Facets are planar polygons without holes
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defined by the circular sequence of halfedges along their boundary.
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The polyhedral surface itself can have holes. The halfedges
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between two endpoints. Facets are planar, possibly non-convex, polygons
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without holes defined by the circular sequence of halfedges along their
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boundary. The polyhedral surface itself can have holes. The halfedges
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along the boundary of a hole are called <I>border halfedges</I> and
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have no incident facet. An edge is a <I>border edge</I> if one of
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its halfedges is a border halfedge. A surface is <I>closed</I> if it
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contains no border halfedges. A closed surface is a boundary
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representation for polyhedra in three dimensions. The convention is
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representation for a polyhedron in three dimensions. The convention is
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that the halfedges are oriented counterclockwise around facets as seen
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from the outside of the polyhedron. An implication is that the
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halfedges are oriented clockwise around the vertices. The notion of
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@ -32,7 +32,7 @@ namespace CGAL {
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always an orientable and oriented 2-manifold with border edges, i.e.,
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the neighborhood of each point on the polyhedral surface is either
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homeomorphic to a disc or to a half disc, except for vertices where
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many holes and surfaces with boundary can join. Another implication is
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multiple holes join. Another implication is
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that the smallest representable surface is a triangle (for polyhedral
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surfaces with border edges) or a tetrahedron (for polyhedra). Boundary
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representations of orientable 2-manifolds are closed under Euler
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@ -15,7 +15,7 @@ edges, facets and an incidence relationship on them. The organization
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beneath is a halfedge data structure, which restricts the class of
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representable surfaces to orientable 2-manifolds - with and without
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boundary. If the surface is closed we call it a <I>polyhedron</I>, for
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example, see the following model of a hammerhead:
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example, see the following model of a hammerhead:
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\image html shark.png
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\image latex shark.png
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@ -26,8 +26,8 @@ the combinatorial integrity of them. It is based on the highly
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flexible design of the halfedge data structure, see the introduction
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in Chapter \ref chapterHalfedgeDS "Halfedge Data Structures" and \cgalCite{k-ugpdd-99}. However, the
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polyhedral surface can be used and understood without knowing the
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underlying design. Some of the examples in this chapter introduce also
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gradually into first applications of this flexibility.
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underlying design. Some of the examples in this chapter gradually
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introduce applications of this flexibility.
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\section PolyhedronDefinition Definition
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@ -41,13 +41,15 @@ halfedge are illustrated in the following figure:
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\image latex halfedge_small.png
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Vertices represent points in space. Edges are straight line segments
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between two endpoints. Facets are planar polygons without
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between two endpoints. Facets are planar, possibly non-convex, polygons without
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holes. Facets are defined by the circular sequence of halfedges along
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their boundary. The polyhedral surface itself can have holes (with at
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least two facets surrounding it since a single facet cannot have a
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hole). The halfedges along the boundary of a hole are called <I>border halfedges</I> and have no incident facet. An edge is a <I>border edge</I> if one of its halfedges is a border halfedge. A
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hole). The halfedges along the boundary of a hole are called
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<I>border halfedges</I> and have no incident facet. An edge is a
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<I>border edge</I> if one of its halfedges is a border halfedge. A
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surface is <I>closed</I> if it contains no border halfedges. A closed
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surface is a boundary representation for polyhedra in three
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surface is a boundary representation for a polyhedron in three
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dimensions. The convention is that the halfedges are oriented
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counterclockwise around facets as seen from the outside of the
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polyhedron. An implication is that the halfedges are oriented
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@ -62,7 +64,7 @@ implication of this definition is that the polyhedral surface is
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always an orientable and oriented 2-manifold with border edges, i.e.,
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the neighborhood of each point on the polyhedral surface is either
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homeomorphic to a disc or to a half disc, except for vertices where
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many holes and surfaces with boundary can join. Another implication is
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multiple holes join. Another implication is
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that the smallest representable surface avoiding self intersections is
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a triangle (for polyhedral surfaces with border edges) or a
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tetrahedron (for polyhedra). Boundary representations of orientable
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