glPolygonMode

The glPolygonMode function selects a polygon rasterization mode.

void glPolygonMode(
  GLenum face,
  GLenum mode
);

Parameters

face
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
The way polygons will be rasterized. The following modes are defined and can be specified in mode. The default is GL_FILL for both front- and back-facing polygons.
Value Meaning
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.

Remarks

The glPolygonMode function controls the interpretation of polygons for rasterization. The face parameter 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.

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 OpenGL when it decomposes polygons, and they can be set explicitly using glEdgeFlag.

The following function retrieves information related to glPolygonMode:

glGet with argument GL_POLYGON_MODE

Error Codes

The following are the error codes and their conditions.

Error code Condition
GL_INVALID_ENUM Either face or mode was not an accepted value.
GL_INVALID_OPERATION glPolygonMode was called between a call to glBegin and the corresponding call to glEnd.

Requirements

  Windows NT/2000: Requires Windows NT 3.5 or later.
  Windows 95/98: Requires Windows 95 or later. Available as a redistributable for Windows 95.
  Header: Declared in Gl.h.
  Library: Use Opengl32.lib.

See Also

glBegin, glEdgeFlag, glEnd, glLineStipple, glLineWidth, glPointSize, glPolygonStipple


  

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