glBegin — delimit the vertices of a primitive or a group of like primitives
Specifies the primitive or primitives that will be created from vertices
glBegin and the subsequent glEnd.
Ten symbolic constants are accepted:
glBegin and glEnd delimit the vertices that define a primitive or
a group of like primitives.
glBegin accepts a single argument that specifies in which of ten ways the
vertices are interpreted.
as an integer count starting at one,
as the total number of vertices specified,
the interpretations are as follows:
Treats each vertex as a single point. Vertex defines point . points are drawn.
Treats each pair of vertices as an independent line segment. Vertices and define line . lines are drawn.
Draws a connected group of line segments from the first vertex to the last. Vertices and define line . lines are drawn.
Draws a connected group of line segments from the first vertex to the last, then back to the first. Vertices and define line . The last line, however, is defined by vertices and . lines are drawn.
Treats each triplet of vertices as an independent triangle. Vertices , , and define triangle . triangles are drawn.
Draws a connected group of triangles. One triangle is defined for each vertex presented after the first two vertices. For odd , vertices , , and define triangle . For even , vertices , , and define triangle . triangles are drawn.
Draws a connected group of triangles. One triangle is defined for each vertex presented after the first two vertices. Vertices , , and define triangle . triangles are drawn.
Treats each group of four vertices as an independent quadrilateral. Vertices , , , and define quadrilateral . quadrilaterals are drawn.
Draws a connected group of quadrilaterals. One quadrilateral is defined for each pair of vertices presented after the first pair. Vertices , , , and define quadrilateral . quadrilaterals are drawn. Note that the order in which vertices are used to construct a quadrilateral from strip data is different from that used with independent data.
Draws a single, convex polygon. Vertices through define this polygon.
Only a subset of GL commands can be used between
glBegin and glEnd.
The commands are
it is acceptable to use
glCallLists to execute
display lists that include only the preceding commands.
If any other GL command is executed between
glBegin and glEnd,
the error flag is set and the command is ignored.
Regardless of the value chosen for
there is no limit to the number of vertices that can be defined
glBegin and glEnd.
and polygons that are incompletely specified are not drawn.
Incomplete specification results when either too few vertices are
provided to specify even a single primitive or when an incorrect multiple
of vertices is specified. The incomplete primitive is ignored; the rest are drawn.
The minimum specification of vertices
for each primitive is as follows:
1 for a point,
2 for a line,
3 for a triangle,
4 for a quadrilateral,
and 3 for a polygon.
Modes that require a certain multiple of vertices are
GL_INVALID_ENUM is generated if
mode is set to an unaccepted value.
GL_INVALID_OPERATION is generated if
glBegin is executed between a
and the corresponding execution of glEnd.
GL_INVALID_OPERATION is generated if glEnd is executed without being
preceded by a
GL_INVALID_OPERATION is generated if a command other than
glCallLists is executed between
the execution of
glBegin and the corresponding
glPixelStore is not allowed after a call to
glBegin and before
the corresponding call to glEnd,
but an error may or may not be generated.
glArrayElement, glCallList, glCallLists, glColor, glEdgeFlag, glEvalCoord, glEvalPoint, glFogCoord, glIndex, glMaterial, glMultiTexCoord, glNormal, glSecondaryColor, glTexCoord, glVertex, glVertexAttrib
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see https://web.archive.org/web/20171022161616/http://oss.sgi.com/projects/FreeB/.