OpenGLContext.scenegraph.polygontessellator

Class for tessellating polygons using GLU

Classes

class PolygonTessellator( object ):

Simplified polygon tessellation for IndexedFaceSets & Fonts

OpenGLContext 2.0.0b1 has substantially improved this class, allowing for multiple-contour tessellation, as well as providing mechanisms for returning results other than triangle-sets.

XXX Should have threading lock around tessContours, as any single tessellator is non-thread-safe. XXX Should be doing a GLU version check for this entire module, and degrading to earlier API version if necessary.

controller

__init__( self , windingRule = GLU_TESS_WINDING_ODD , ccw = True )

Initialise the PolygonTessellator

begin( self , dataType , polygonData = None )

Begin a new tessellation sequence (GLU Tess callback)

combine( self , newPosition , vertices , weights , polygonData = None )

Blend vertices with weights to create new vertex object (GLU Tess callback)

end( self , * args , ** namedargs )

Record the end of a tessellated shape (GLU Tess callback)

This method implements the "forceTriangles" semantics by unravelling GL_TRIANGLE_FAN or GL_TRIANGLE_STRIP if forceTriangles is true. It also manages the creating of the final self.result data-set.

reset( self , forceTriangles = 1 )

Reset the tessellator for a new polygon

tessContours( self , contours , forceTriangles = 1 , normal = None )

Tessellate polygon defined by (multiple) contours

Occasionally will create new vertices as a blending of the given vertex objects.

contours: list of list of vertices, with each set defining a closed contour within the polygon.

forceTriangles: if true (default), returns a set of GL_TRIANGLES-compatible vertex specifications as a list-of-vertex-objects [ Vertex(), Vertex(), ...]

if false, returns vertices), ... where type is the type to be specified for glBegin, and vertices are a list-of-vertex-objects, with the types being any of GL_TRIANGLES, GL_TRIANGLE_STRIP, or GL_TRIANGLE_FAN and the vertices being compatible with the given type.

normal: if specified, calls gluTessNormal with the value, restores to default after the tessellation is complete

return value -- see note on forceTriangles

tessellate( self , vertices , forceTriangles = 1 )

Tessellate polygon defined by vertices

Less general form of tessContours, takes a single contour and returns the tessellation result for that contour. See tessContours for semantics of forceTriangles and the results (which are dependent on the value of forceTriangles).

vertex( self , vertex , polygonData = None )