MirOS Manual: glBegin(3), glEnd(3)


GLBEGIN(3G)         UNIX Programmer's Manual          GLBEGIN(3G)

NAME

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

C SPECIFICATION

     void 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 glEnd( void )

DESCRIPTION

     glBegin and glEnd delimit the vertices that define a primi-
     tive 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:

     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 seg-
                            ments from the first vertex to the
                            last. Vertices n and n + 1 define
                            line n. N-1 lines are drawn.

     GL_LINE_LOOP           Draws a connected group of line seg-
                            ments from the first vertex to the
                            last, then back to the first. Ver-
                            tices 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

MirOS BSD #10-current  Printed 03.04.2017                       1

GLBEGIN(3G)         UNIX Programmer's Manual          GLBEGIN(3G)

                            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 triangle is defined for each ver-
                            tex 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 trian-
                            gles are drawn.

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

     GL_QUADS               Treats each group of four vertices as
                            an independent quadrilateral. Ver-
                            tices 4n-3, 4n-2, 4n-1, and 4n define
                            quadrilateral n. N/4 quadrilaterals
                            are drawn.

     GL_QUAD_STRIP          Draws a connected group of quadrila-
                            terals. One quadrilateral is defined
                            for each pair of vertices presented
                            after the first pair. Vertices 2n-1,
                            2n, 2n + 2, and 2n + 1 define quadri-
                            lateral n. N/2-1 quadrilaterals are
                            drawn. Note that the order in which
                            vertices are used to construct a qua-
                            drilateral from strip data is dif-
                            ferent from that used with indepen-
                            dent data.

     GL_POLYGON             Draws a single, convex polygon. Ver-
                            tices 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.

MirOS BSD #10-current  Printed 03.04.2017                       2

GLBEGIN(3G)         UNIX Programmer's Manual          GLBEGIN(3G)

     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 ver-
     tices 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).

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 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.

SEE ALSO

     glArrayElement(3G), glCallList(3G), glCallLists(3G),
     glColor(3G), glEdgeFlag(3G), glEvalCoord(3G),
     glEvalPoint(3G), glIndex(3G), glMaterial(3G), glNormal(3G),
     glTexCoord(3G), glVertex(3G)

MirOS BSD #10-current  Printed 03.04.2017                       3

Generated on 2017-04-03 16:26:17 by $MirOS: src/scripts/roff2htm,v 1.88 2017/01/29 00:51:06 tg Exp $

These manual pages and other documentation are copyrighted by their respective writers; their source is available at our CVSweb, AnonCVS, and other mirrors. The rest is Copyright © 2002–2017 The MirOS Project, Germany.
This product includes material provided by mirabilos.

This manual page’s HTML representation is supposed to be valid XHTML/1.1; if not, please send a bug report — diffs preferred.