HOpenGL Libraries (OpenGL package)ContentsIndex
Graphics.Rendering.OpenGL.GLU.Tessellation
Portabilityportable
Stabilityprovisional
Maintainersven.panne@aedion.de
Contents
Polygon description
Combining vertices
Tessellation parameters
Tessellator type
Contour extraction
Triangulation
Tessellation into primitives
Description
This module corresponds to chapter 5 (Polygon Tessellation) of the GLU specs.
Synopsis
data AnnotatedVertex v = AnnotatedVertex (Vertex3 GLdouble) v
newtype ComplexContour v = ComplexContour [AnnotatedVertex v]
newtype ComplexPolygon v = ComplexPolygon [ComplexContour v]
data WeightedProperties v = WeightedProperties (GLclampf, v) (GLclampf, v) (GLclampf, v) (GLclampf, v)
type Combiner v = Vertex3 GLdouble -> WeightedProperties v -> v
data TessWinding
= TessWindingOdd
| TessWindingNonzero
| TessWindingPositive
| TessWindingNegative
| TessWindingAbsGeqTwo
type Tolerance = GLdouble
type Tessellator p v = TessWinding -> Tolerance -> Normal3 GLdouble -> Combiner v -> ComplexPolygon v -> IO (p v)
newtype SimpleContour v = SimpleContour [AnnotatedVertex v]
newtype PolygonContours v = PolygonContours [SimpleContour v]
extractContours :: Storable v => Tessellator PolygonContours v
type TriangleVertex v = AnnotatedVertex (v, EdgeFlag)
data Triangle v = Triangle (TriangleVertex v) (TriangleVertex v) (TriangleVertex v)
newtype Triangulation v = Triangulation [Triangle v]
triangulate :: Storable v => Tessellator Triangulation v
data Primitive v = Primitive PrimitiveMode [AnnotatedVertex v]
newtype SimplePolygon v = SimplePolygon [Primitive v]
tessellate :: Storable v => Tessellator SimplePolygon v
Polygon description
data AnnotatedVertex v
The basic building block in tessellation is a 3D vertex with an associated property, e.g. color, texture coordinates, etc.
Constructors
AnnotatedVertex (Vertex3 GLdouble) v
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newtype ComplexContour v
A complex contour, which can be self-intersecting and/or concave.
Constructors
ComplexContour [AnnotatedVertex v]
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newtype ComplexPolygon v
A complex (possibly concave) polygon, represented by one or more complex and possibly intersecting contours.
Constructors
ComplexPolygon [ComplexContour v]
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Combining vertices
data WeightedProperties v
Four vertex properties (cf. AnnotatedVertex) with associated weigths summing up to 1.0.
Constructors
WeightedProperties (GLclampf, v) (GLclampf, v) (GLclampf, v) (GLclampf, v)
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type Combiner v = Vertex3 GLdouble -> WeightedProperties v -> v
A function combining given vertex properties into a property for a newly generated vertex
Tessellation parameters
data TessWinding
Constructors
TessWindingOdd
TessWindingNonzero
TessWindingPositive
TessWindingNegative
TessWindingAbsGeqTwo
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type Tolerance = GLdouble

The relative tolerance under which two vertices can be combined (see Combiner). Multiplication with the largest coordinate magnitude of all polygon vertices yields the maximum distance between two mergeable vertices.

Note that merging is optional and the tolerance is only a hint.

Tessellator type
type Tessellator p v = TessWinding -> Tolerance -> Normal3 GLdouble -> Combiner v -> ComplexPolygon v -> IO (p v)

A general tessellator type.

Before tessellation of a complex polygon, all its vertices are projected into a plane perpendicular to the given normal. If the given normal is Normal3 0 0 0, a fitting plane of all vertices is used.

Contour extraction
newtype SimpleContour v
A simple, non-self-intersecting contour
Constructors
SimpleContour [AnnotatedVertex v]
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newtype PolygonContours v
The contours of a complex polygon, represented by one or more non-intersecting simple contours
Constructors
PolygonContours [SimpleContour v]
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extractContours :: Storable v => Tessellator PolygonContours v
Triangulation
type TriangleVertex v = AnnotatedVertex (v, EdgeFlag)
A triangle vertex with additional information about the edge it begins
data Triangle v
A triangle, represented by three triangle vertices
Constructors
Triangle (TriangleVertex v) (TriangleVertex v) (TriangleVertex v)
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Eq v => Eq (Triangle v)
Ord v => Ord (Triangle v)
newtype Triangulation v
A triangulation of a complex polygon
Constructors
Triangulation [Triangle v]
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triangulate :: Storable v => Tessellator Triangulation v
Tessellation into primitives
data Primitive v
Constructors
Primitive PrimitiveMode [AnnotatedVertex v]
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Eq v => Eq (Primitive v)
Ord v => Ord (Primitive v)
newtype SimplePolygon v
Constructors
SimplePolygon [Primitive v]
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tessellate :: Storable v => Tessellator SimplePolygon v
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