1991-2006
Silicon Graphics, Inc.
glPolygonMode
3G
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 how polygons will be rasterized.
Accepted values are
GL_POINT,
GL_LINE, and
GL_FILL.
The initial value 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; 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
Copyright
Copyright 1991-2006
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
http://oss.sgi.com/projects/FreeB/.