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## GLBEGINIndex## NAMEglBegin, glEnd
- delimit the vertices of a primitive or a group of like primitives
## C SPECIFICATIONvoid f3glBeginfP( GLenum fImodefP )## PARAMETERS- f2modefP
- Specifies the primitive or primitives that will be created from vertices presented between %f3glBeginfP and the subsequent %f3glEndfP. Ten symbolic constants are accepted: %f3GL_POINTSfP, %f3GL_LINESfP, %f3GL_LINE_STRIPfP, %f3GL_LINE_LOOPfP, %f3GL_TRIANGLESfP, %f3GL_TRIANGLE_STRIPfP, %f3GL_TRIANGLE_FANfP, %f3GL_QUADSfP, %f3GL_QUAD_STRIPfP, and %f3GL_POLYGONfP.
## C SPECIFICATIONvoid f3glEndfP( void )## DESCRIPTION%f3glBeginfP and %f3glEndfP delimit the vertices that define a primitive or a group of like primitives. %f3glBeginfP 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:- %f3GL_POINTSfP
- Treats each vertex as a single point. Vertex $n$ defines point $n$. $N$ points are drawn.
- %f3GL_LINESfP
- Treats each pair of vertices as an independent line segment. Vertices $2n^-^1$ and $2n$ define line $n$. $N/2$ lines are drawn.
- %f3GL_LINE_STRIPfP
- 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.
- %f3GL_LINE_LOOPfP
- 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.
- %f3GL_TRIANGLESfP
- Treats each triplet of vertices as an independent triangle. Vertices $3n^-^2$, $3n^-^1$, and $3n$ define triangle $n$. $N/3$ triangles are drawn.
- %f3GL_TRIANGLE_STRIPfP
- 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.
- %f3GL_TRIANGLE_FANfP
- 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.
- %f3GL_QUADSfP
- 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.
- %f3GL_QUAD_STRIPfP
- 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.
- %f3GL_POLYGONfP
- Draws a single, convex polygon. Vertices $1$ through $N$ define this polygon. Only a subset of GL commands can be used between %f3glBeginfP and %f3glEndfP. The commands are %f3glVertexfP, %f3glColorfP, %f3glIndexfP, %f3glNormalfP, %f3glTexCoordfP, %f3glEvalCoordfP, %f3glEvalPointfP, %f3glArrayElementfP, %f3glMaterialfP, and %f3glEdgeFlagfP. Also, it is acceptable to use %f3glCallListfP or %f3glCallListsfP to execute display lists that include only the preceding commands. If any other GL command is executed between %f3glBeginfP and %f3glEndfP, the error flag is set and the command is ignored. Regardless of the value chosen for f2modefP, there is no limit to the number of vertices that can be defined between %f3glBeginfP and %f3glEndfP. 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 %f3GL_LINESfP (2), %f3GL_TRIANGLESfP (3), %f3GL_QUADSfP (4), and %f3GL_QUAD_STRIPfP (2).
## ERRORS%f3GL_INVALID_ENUMfP is generated if f2modefP is set to an unaccepted value. %f3GL_INVALID_OPERATIONfP is generated if %f3glBeginfP is executed between a %f3glBeginfP and the corresponding execution of %f3glEndfP. %f3GL_INVALID_OPERATIONfP is generated if %f3glEndfP is executed without being preceded by a %f3glBeginfP. %f3GL_INVALID_OPERATIONfP is generated if a command other than %f3glVertexfP, %f3glColorfP, %f3glIndexfP, %f3glNormalfP, %f3glTexCoordfP, %f3glEvalCoordfP, %f3glEvalPointfP, %f3glArrayElementfP, %f3glMaterialfP, %f3glEdgeFlagfP, %f3glCallListfP, or %f3glCallListsfP is executed between the execution of %f3glBeginfP and the corresponding execution %f3glEndfP. Execution of %f3glEnableClientStatefP, %f3glDisableClientStatefP, %f3glEdgeFlagPointerfP, %f3glTexCoordPointerfP, %f3glColorPointerfP, %f3glIndexPointerfP, %f3glNormalPointerfP,%f3glVertexPointerfP, %f3glInterleavedArraysfP, or %f3glPixelStorefP is not allowed after a call to %f3glBeginfP and before the corresponding call to %f3glEndfP, but an error may or may not be generated. ## SEE ALSO%f3glArrayElement(3G)fP, %f3glCallList(3G)fP, %f3glCallLists(3G)fP, %f3glColor(3G)fP, %f3glEdgeFlag(3G)fP, %f3glEvalCoord(3G)fP,%f3glEvalPoint(3G)fP, %f3glIndex(3G)fP, %f3glMaterial(3G)fP, %f3glNormal(3G)fP, %f3glTexCoord(3G)fP, %f3glVertex(3G)fP
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