NAME

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

C SPECIFICATION

void ggllBBeeggiinn( GLenum _m_o_d_e )

        

delim $$

PARAMETERS

_m_o_d_e
Specifies the primitive or primitives that will be created from vertices presented between ggllBBeeggiinn and the subsequent ggllEEnndd. Ten symbolic constants are accepted: GGLL__PPOOIINNTTSS, GGLL__LLIINNEESS, GGLL__LLIINNEE__SSTTRRIIPP, GGLL__LLIINNEE__LLOOOOPP, GGLL__TTRRIIAANNGGLLEESS, GGLL__TTRRIIAANNGGLLEE__SSTTRRIIPP, GGLL__TTRRIIAANNGGLLEE__FFAANN, GGLL__QQUUAADDSS, GGLL__QQUUAADD__SSTTRRIIPP, and GGLL__PPOOLLYYGGOONN.

C SPECIFICATION

void ggllEEnndd( void )

        

DESCRIPTION

ggllBBeeggiinn and ggllEEnndd delimit the vertices that define a primitive or a group of like primitives. ggllBBeeggiinn 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:
GGLL__PPOOIINNTTSS
Treats each vertex as a single point. Vertex $n$ defines point $n$. $N$ points are drawn.
GGLL__LLIINNEESS
Treats each pair of vertices as an independent line segment. Vertices $2n^-^1$ and $2n$ define line $n$. $N/2$ lines are drawn.
GGLL__LLIINNEE__SSTTRRIIPP
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.
GGLL__LLIINNEE__LLOOOOPP
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.
GGLL__TTRRIIAANNGGLLEESS
Treats each triplet of vertices as an independent triangle. Vertices $3n^-^2$, $3n^-^1$, and $3n$ define triangle $n$. $N/3$ triangles are drawn.
GGLL__TTRRIIAANNGGLLEE__SSTTRRIIPP
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.
GGLL__TTRRIIAANNGGLLEE__FFAANN
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.
GGLL__QQUUAADDSS
Treats each group of four vertices as an independent quadrilateral. Vertices $4n^-^3$, $4n^-^2$, $4n^-^1$, and $4n$ define quadrilateral $n$. $N/4$ quadrilaterals are drawn.
GGLL__QQUUAADD__SSTTRRIIPP
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 $n$. $N/2^-^1$ 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.
GGLL__PPOOLLYYGGOONN
Draws a single, convex polygon. Vertices $1$ through $N$ define this polygon.

Only a subset of GL commands can be used between ggllBBeeggiinn and ggllEEnndd. The commands are ggllVVeerrtteexx, ggllCCoolloorr, ggllIInnddeexx, ggllNNoorrmmaall, ggllTTeexxCCoooorrdd, ggllEEvvaallCCoooorrdd, ggllEEvvaallPPooiinntt, ggllAArrrraayyEElleemmeenntt, ggllMMaatteerriiaall, and ggllEEddggeeFFllaagg. Also, it is acceptable to use ggllCCaallllLLiisstt or ggllCCaallllLLiissttss to execute display lists that include only the preceding commands. If any other GL command is executed between ggllBBeeggiinn and ggllEEnndd, the error flag is set and the command is ignored.

Regardless of the value chosen for _m_o_d_e, there is no limit to the number of vertices that can be defined between ggllBBeeggiinn and ggllEEnndd. 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 GGLL__LLIINNEESS (2), GGLL__TTRRIIAANNGGLLEESS (3), GGLL__QQUUAADDSS (4), and GGLL__QQUUAADD__SSTTRRIIPP (2).

ERRORS

GGLL__IINNVVAALLIIDD__EENNUUMM is generated if _m_o_d_e is set to an unaccepted value.

GGLL__IINNVVAALLIIDD__OOPPEERRAATTIIOONN is generated if ggllBBeeggiinn is executed between a ggllBBeeggiinn and the corresponding execution of ggllEEnndd.

GGLL__IINNVVAALLIIDD__OOPPEERRAATTIIOONN is generated if ggllEEnndd is executed without being preceded by a ggllBBeeggiinn.

GGLL__IINNVVAALLIIDD__OOPPEERRAATTIIOONN is generated if a command other than ggllVVeerrtteexx, ggllCCoolloorr, ggllIInnddeexx, ggllNNoorrmmaall, ggllTTeexxCCoooorrdd, ggllEEvvaallCCoooorrdd, ggllEEvvaallPPooiinntt, ggllAArrrraayyEElleemmeenntt, ggllMMaatteerriiaall, ggllEEddggeeFFllaagg, ggllCCaallllLLiisstt, or ggllCCaallllLLiissttss is executed between the execution of ggllBBeeggiinn and the corresponding execution ggllEEnndd.

Execution of ggllEEnnaabblleeCClliieennttSSttaattee, ggllDDiissaabblleeCClliieennttSSttaattee, ggllEEddggeeFFllaaggPPooiinntteerr, ggllTTeexxCCoooorrddPPooiinntteerr, ggllCCoolloorrPPooiinntteerr, ggllIInnddeexxPPooiinntteerr, ggllNNoorrmmaallPPooiinntteerr,
ggllVVeerrtteexxPPooiinntteerr, ggllIInntteerrlleeaavveeddAArrrraayyss, or ggllPPiixxeellSSttoorree is not allowed after a call to ggllBBeeggiinn and before the corresponding call to ggllEEnndd, but an error may or may not be generated.

SEE ALSO

ggllAArrrraayyEElleemmeenntt((33GG)), ggllCCaallllLLiisstt((33GG)), ggllCCaallllLLiissttss((33GG)), ggllCCoolloorr((33GG)), ggllEEddggeeFFllaagg((33GG)), ggllEEvvaallCCoooorrdd((33GG)),
ggllEEvvaallPPooiinntt((33GG)), ggllIInnddeexx((33GG)), ggllMMaatteerriiaall((33GG)), ggllNNoorrmmaall((33GG)), ggllTTeexxCCoooorrdd((33GG)), ggllVVeerrtteexx((33GG))