GLBEGIN(3G) GLBEGIN(3G)

glBegin, glEnd - delimit the vertices of a primitive or a group of like primitives

C SPECIFICATION

void glBegin( GLenum 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 glEnd( void )












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.
    Taking n as an integer count starting at one, and N as the total number of
    vertices specified, the interpretations are as follows:



  

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

  

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

  

  
Draws a connected group of line segments from the first vertex to the
      last. Vertices n and n+1 define line n. n-1 lines are drawn.

  

  
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.

  

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

  

  
Draws a connected group of triangles. One triangle 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, vertices n+1, n, and n+2 define
      triangle n. n-2 triangles are drawn.

  

  
Draws a connected group of triangles. One triangle 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.

  

  
Treats each group of four vertices as an independent quadrilateral.
      Vertices 4n-3, 4n-2, 4n-3, and 4n define quadrilateral n. n/4
      quadrilaterals are drawn.

  

  
Draws a connected group of quadrilaterals. One quadrilateral is defined
      for each pair of vertices presented after the first pair. Vertices 2n-1,
      2n, 2n+2, and 2n+1 define quadrilateral n. n/2 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 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 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 mode, there is no limit
    to the number of vertices that can be defined between glBegin and
    glEnd. Lines, triangles, quadrilaterals, 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_LINES (2), GL_TRIANGLES (3), GL_QUADS
    (4), and GL_QUAD_STRIP (2).








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 execution glEnd.


Execution of glEnableClientState,
    glDisableClientState, glEdgeFlagPointer,
    glTexCoordPointer, glColorPointer, glIndexPointer,
    glNormalPointer,
  

  glVertexPointer, glInterleavedArrays, or 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, glIndex, glMaterial, glNormal,
    glTexCoord, glVertex