glPolygonMode — select a polygon rasterization mode
void glPolygonMode( | GLenum | face, |
| GLenum | mode); |
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.
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.
To draw a surface with filled back-facing polygons and outlined front-facing polygons, call
glPolygonMode(GL_FRONT,GL_LINE);
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.
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.
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