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OpenGL 1.1 for AIX: Reference Manual

glEdgeFlag Subroutine


Marks edges as either boundary or nonboundary.


OpenGL C bindings library: libGL.a

C Syntax

void glEdgeFlag(GLboolean Flag)
void glEdgeFlagv(const GLboolean *Flagv)


Flag Specifies the current edge flag value, either True or False.
Flagv Specifies a pointer to an array that contains a single Boolean element (either True or False). Replaces the current edge flag value.


Each vertex of a polygon, separate triangle, or separate quadrilateral specified between glBegin and glEnd is marked as the start of either a boundary or nonboundary edge. If the current edge flag is True when the vertex is specified, the vertex is marked as the start of a boundary edge. Otherwise, the vertex is marked as the start of a nonboundary edge. glEdgeFlag sets the edge flag to True if the Flag parameter is nonzero; otherwise, the edge flag is set to False.

The vertices of connected triangles and connected quadrilaterals are always marked as a boundary, regardless of the value of the edge flag.

Boundary and nonboundary edge flags on vertices are significant only if GL_POLYGON_MODE is set to GL_POINT or GL_LINE. See glPolygonMode.

Initially, the edge flag bit is True.


The current edge flag can be updated at any time. In particular, glEdgeFlag can be called between a call to glBegin and the corresponding call to glEnd.

Associated Gets

Associated gets for the glEdgeFlag subroutine are as follows. (See the glGet subroutine for more information.)

glGet with argument GL_EDGE_FLAG.


/usr/include/GL/gl.h Contains C language constants, variable type definitions, and ANSI function prototypes for OpenGL.

Related Information

The glBegin subroutine, glEdgeFlagPointer subroutine, glEdgeFlagPointerEXT subroutine, glEnd subroutine, glPolygonMode subroutine.

OpenGL Overview.

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