API: glPolygonMode --Select a polygon rasterization mode.

[References]

1. "glPolygonMode, from opengl.org/sdk/docs/man4/.."
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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_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 andGL_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.

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