void GLAPIENTRY glBegin( GLenum mode )

PARAMETERS
       mode  Specifies the primitive or primitives that will  be  created  from
             vertices  presented between glBegin and the subsequent glEnd.  Ten
             symbolic   constants   are    accepted:    GL_POINTS,    GL_LINES,
             GL_LINE_STRIP,   GL_LINE_LOOP,   GL_TRIANGLES,  GL_TRIANGLE_STRIP,
             GL_TRIANGLE_FAN, GL_QUADS, GL_QUAD_STRIP, and GL_POLYGON.

C SPECIFICATION
       void GLAPIENTRY glEnd( void )

DESCRIPTION
       glBegin and glEnd delimit the vertices that  define  a  primitive  or  a
       group of like primitives.  glBegin accepts a single argument that speci‐
       fies in which of ten ways the vertices are interpreted.  Taking n as  an
       integer  count  starting  at  one, and N as the total number of vertices
       specified, the interpretations are as follows:

       GL_POINTS              Treats each vertex as a single point.   Vertex  n
                              defines point n.  N points are drawn.

       GL_LINES               Treats  each  pair  of vertices as an independent
                              line segment.  Vertices 2n−1 and 2n  define  line
                              n.  N/2 lines are drawn.

       GL_LINE_STRIP          Draws a connected group of line segments from the
                              first vertex to the last.  Vertices n and n+1 de‐
                              fine line n.  N−1 lines are drawn.

       GL_LINE_LOOP           Draws a connected group of line segments from the
                              first vertex to the last, then back to the first.
                              Vertices n and n+1 define line n.  The last line,
                              however, is defined by vertices N and 1.  N lines
                              are drawn.

       GL_TRIANGLES           Treats each triplet of vertices as an independent
                              triangle.  Vertices 3n−2,  3n−1,  and  3n  define
                              triangle n.  N/3 triangles are drawn.

       GL_TRIANGLE_STRIP      Draws a connected group of triangles.  One trian‐
                              gle is defined for each  vertex  presented  after
                              the  first  two vertices.  For odd n, vertices n,
                              n+1, and n+2 define triangle n.  For even n, ver‐
                              tices  n+1,  n,  and  n+2 define triangle n.  N−2
                              triangles are drawn.

       GL_TRIANGLE_FAN        Draws a connected group of triangles.  One trian‐
                              gle  is  defined  for each vertex presented after
                              the first two vertices.  Vertices 1, n+1, and n+2
                              define triangle n.  N−2 triangles are drawn.

       GL_POLYGON             Draws  a  single,  convex  polygon.   Vertices  1
                              through N define this polygon.

       Only a subset of GL commands can be used between glBegin and glEnd.  The
       commands   are   glVertex,   glColor,   glIndex,  glNormal,  glTexCoord,
       glEvalCoord, glEvalPoint, glArrayElement,  glMaterial,  and  glEdgeFlag.
       Also,  it is acceptable to use glCallList or glCallLists to execute dis‐
       play 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 mode, there is no limit to the number
       of  vertices that can be defined between glBegin and glEnd.  Lines, tri‐
       angles, quadrilaterals, and polygons that are incompletely specified are
       not  drawn.   Incomplete  specification results when either too few ver‐
       tices are provided to specify even a single primitive or when an  incor‐
       rect  multiple of vertices is specified. The incomplete primitive is ig‐
       nored; 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_LINES (2), GL_TRIANGLES (3), GL_QUADS (4), and GL_QUAD_STRIP (2).

ERRORS
       GL_INVALID_ENUM is generated if mode is set to an unaccepted value.

       GL_INVALID_OPERATION  is  generated  if  glBegin  is  executed between a
       glBegin and the corresponding execution of glEnd.

       GL_INVALID_OPERATION is generated if glEnd  is  executed  without  being
       preceded by a glBegin.

       GL_INVALID_OPERATION  is  generated  if  a  command other than glVertex,
       glColor,  glIndex,  glNormal,  glTexCoord,   glEvalCoord,   glEvalPoint,
       glArrayElement,  glMaterial,  glEdgeFlag,  glCallList, or glCallLists is
       executed between the execution of glBegin and the  corresponding  execu‐
       tion glEnd.

       Execution       of       glEnableClientState,      glDisableClientState,
       glEdgeFlagPointer,  glTexCoordPointer,  glColorPointer,  glIndexPointer,
       glNormalPointer,
       glVertexPointer, glInterleavedArrays, or glPixelStore is not allowed af‐
       ter a call to glBegin and before the corresponding call to glEnd, but an
       error may or may not be generated.

SEE ALSO
       glArrayElement,    glCallList,    glCallLists,    glColor,   glEdgeFlag,
       glEvalCoord,
       glEvalPoint, glIndex, glMaterial, glNormal, glTexCoord, glVertex

                                                                    GLBEGIN(3G)