man glPolygonMode (3): 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_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: both front and back-facing polygons (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. 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_SMOOTH control the rasterization of the polygon.

EXAMPLES

To draw a surface with outlined polygons, call

glPolygonMode(GL_FRONT_AND_BACK, 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 triangle stips and fans.

ERRORS

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

ASSOCIATED GETS

glGet() with argument GL_POLYGON_MODE