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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