OpenGLContext.scenegraph.polygon

Holder for metadata regarding a polygon

Functions

Get the 3D magnitude of a 3-coordinate vector

Classes

class DegeneratePolygon( object ):

Class encapsulated a degenerate triangle definition

At the moment this is not a particularly useful class, eventually it might be used for interactive debugging of the geometry (for instance highlighting the degenerate polygons with indexed line sets).

Note: an index of -1 indicates a likely tesselation- generated vertex.

__init__( self , vertices , node = None , reason = '' )

Initialize the DegeneratePolygon instance

vertices: sequence of vertices
node: optional pointer to the source node
reason: string description of the condition which makes this a degenerate polygon definition.

__repr__( self )

class Polygon( list ):

Holder for metadata regarding a particular polygon

Often during certain operations (such as tessellation) is useful to have an object for representing a polygon which binds together all the metadata regarding that polygon.

The Polygon class is modeled as a simple list-of-vertices with a convenience method normalise to make the class easier to use when dealing with triangle-only systems such as the array geometry classes.

__init__( self , polyIndex = -1 , node = None , points = None , ccw = True )

Initialize the polygon

polyIndex: more accurately "polygon ID", an opaque value used to identify the polygon.
node: optional reference to the scenegraph node from which we are derived, used primarily during error reporting to give feedback regarding which node has encountered the error.
points: list of vertices which make up the definition of the polygon.

__repr__( self )

Produce code-like representation of the polygon

checkVertices( self )

Check set of triangle vertices for possible degeneracy

At the moment this checks for condition:

vertices are collinear

Returns only the well formed triangles from the input triangle vertex set. (Note that this is called by normalise, which explains the rather strange input and output).

normalise( self , tessellate = None )

Normalise this polygon to a set of triangle vertices

tesselate: callable which can accept a Polygon instance and return a list of vertices representing a tesselated polygon triangle-set. (And only a triangle- set, no triangle-fans or triangle-strips).