glPolygonMode

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 modeis not an accepted value.

GL_INVALID_OPERATION is generated if glPolygonMode is called between a call to glBegin and the corresponding call to glEnd.

ASSOCIATED GETS

glGet with argument GL_POLYGON_MODE