like primitives

**eqn not supported**

*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**.

**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 $n~+~1$ define 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 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.
**GL_TRIANGLE_FAN**- 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.
**GL_QUADS**- 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.
**GL_QUAD_STRIP**- 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.
**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 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_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.