glPolygonMode.3gl

Name

  glPolygonMode	- select a polygon rasterization mode

C Specification

  void glPolygonMode( GLenum face,
		      GLenum mode )

Parameters

  face	Specifies the polygons that mode applies to.  Must be GL_FRONT for
	front-facing polygons, GL_BACK for back-facing polygons, or
	GL_FRONT_AND_BACK for front- and back-facing polygons.

  mode	Specifies the way polygons will	be rasterized.	Accepted values	are
	GL_POINT, GL_LINE, and GL_FILL.	 The default is	GL_FILL	for both
	front- and back-facing polygons.

Description

  glPolygonMode	controls the interpretation of polygons	for rasterization.
  face describes which polygons	mode applies to: front-facing polygons
  (GL_FRONT), back-facing polygons (GL_BACK), or both (GL_FRONT_AND_BACK).
  The polygon mode affects only	the final rasterization	of polygons.  In
  particular, a	polygon's vertices are lit and the polygon is clipped and
  possibly culled before these modes are applied.

  Three	modes are defined and can be specified in mode:

  GL_POINT	Polygon	vertices that are marked as the	start of a boundary
		edge are drawn as points.  Point attributes such as
		GL_POINT_SIZE and GL_POINT_SMOOTH control the rasterization
		of the points.	Polygon	rasterization attributes other than
		GL_POLYGON_MODE	have no	effect.

  GL_LINE	Boundary edges of the polygon are drawn	as line	segments.
		They are treated as connected line segments for	line
		stippling; the line stipple counter and	pattern	are not	reset
		between	segments (see glLineStipple).  Line attributes such
		as GL_LINE_WIDTH and GL_LINE_SMOOTH control the	rasterization
		of the lines.  Polygon rasterization attributes	other than
		GL_POLYGON_MODE	have no	effect.

  GL_FILL	The interior of	the polygon is filled.	Polygon	attributes
		such as	GL_POLYGON_STIPPLE and GL_POLYGON_SMOOTH control the
		rasterization of the polygon.

Examples

  To draw a surface with filled	back-facing polygons and outlined front-
  facing polygons, call	glPolygonMode(GL_FRONT,	GL_LINE);

Notes

  Vertices are marked as boundary or nonboundary with an edge flag.  Edge
  flags	are generated internally by the	GL when	it decomposes polygons,	and
  they can be set explicitly using glEdgeFlag.

Errors

  GL_INVALID_ENUM is generated if either face or mode is not an	accepted
  value.

  GL_INVALID_OPERATION is generated if glPolygonMode is	executed between the
  execution of glBegin and the corresponding execution of glEnd.

Associated Gets

  glGet	with argument GL_POLYGON_MODE

See Also

  glBegin, glEdgeFlag, glLineStipple, glLineWidth, glPointSize,
  glPolygonStipple

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Last Edited: Fri Dec 6 11:18:03 EST 1996 by AFV
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