void glMap2d( GLenumtarget, GLdoubleu1, GLdoubleu2, GLintustride, GLintuorder, GLdoublev1, GLdoublev2, GLintvstride, GLintvorder, const GLdouble*points) void glMap2f( GLenumtarget, GLfloatu1, GLfloatu2, GLintustride, GLintuorder, GLfloatv1, GLfloatv2, GLintvstride, GLintvorder, const GLfloat*points)

*target*- Specifies the kind of values that are generated by the evaluator.
Symbolic constants
,**GL_MAP2_VERTEX_3**,**GL_MAP2_VERTEX_4**,**GL_MAP2_INDEX**,**GL_MAP2_COLOR_4**,**GL_MAP2_NORMAL**,**GL_MAP2_TEXTURE_COORD_1**,**GL_MAP2_TEXTURE_COORD_2**, and**GL_MAP2_TEXTURE_COORD_3**are accepted.**GL_MAP2_TEXTURE_COORD_4** ,*u1**u2*- Specify a linear mapping of
*u*, as presented to`glEvalCoord2`, to , one of the two variables that are evaluated by the equations specified by this command. Initially,is 0 and*u1*is 1.*u2* *ustride*- Specifies the number of floats or doubles between the beginning of control
point
**R**_{ij}and the beginning of control point**R**_{(i+1)j}, where*i*and*j*are the*u*and*v*control point indices, respectively. This allows control points to be embedded in arbitrary data structures. The only constraint is that the values for a particular control point must occupy contiguous memory locations. The initial value ofis 0.*ustride* *uorder*- Specifies the dimension of the control point array in the
*u*axis. Must be positive. The initial value is 1. ,*v1**v2*- Specify a linear mapping of
*v*, as presented to`glEvalCoord2`, to , one of the two variables that are evaluated by the equations specified by this command. Initially,is 0 and*v1*is 1.*v2* *vstride*- Specifies the number of floats or doubles between the beginning of control
point
**R**_{ij}and the beginning of control point**R**_{i(j+1)}, where*i*and*j*are the*u*and*v*control point indices, respectively. This allows control points to be embedded in arbitrary data structures. The only constraint is that the values for a particular control point must occupy contiguous memory locations. The initial value ofis 0.*vstride* *vorder*- Specifies the dimension of the control point array in the
*v*axis. Must be positive. The initial value is 1. *points*- Specifies a pointer to the array of control points.

All polynomial or rational polynomial splines of any degree (up to the maximum degree supported by the GL implementation) can be described using evaluators. These include almost all surfaces used in computer graphics, including B-spline surfaces, NURBS surfaces, Bezier surfaces, and so on.

Evaluators define surfaces based on bivariate Bernstein polynomials. Define
*p*(, )

where **R**_{ij} is a control point,
*B _{i}^{n}*() is the

and *B _{j}^{m}*() is
the

Recall that

`glMap2` is used to define the basis and to specify what kind of
values are produced. Once defined, a map can be enabled and disabled by
calling `glEnable` and `glDisable` with the map name, one of the nine
predefined values for ` target`, described below. When

` target` is a symbolic constant that indicates what kind of
control points are provided in

**GL_MAP2_VERTEX_3**- Each control point is three floating-point values representing
*x*,*y*, and*z*. Internal`glVertex3`commands are generated when the map is evaluated. **GL_MAP2_VERTEX_4**- Each control point is four floating-point values representing
*x*,*y*,*z*, and*w*. Internal`glVertex4`commands are generated when the map is evaluated. **GL_MAP2_INDEX**- Each control point is a single floating-point value representing a color
index. Internal
`glIndex`commands are generated when the map is evaluated but the current index is not updated with the value of these`glIndex`commands. **GL_MAP2_COLOR_4**- Each control point is four floating-point values representing red, green,
blue, and alpha. Internal
`glColor4`commands are generated when the map is evaluated but the current color is not updated with the value of these`glColor4`commands. **GL_MAP2_NORMAL**- Each control point is three floating-point values representing the
*x*,*y*, and*z*components of a normal vector. Internal`glNormal`commands are generated when the map is evaluated but the current normal is not updated with the value of these`glNormal`commands. **GL_MAP2_TEXTURE_COORD_1**- Each control point is a single floating-point value representing the
*s*texture coordinate. Internal`glTexCoord1`commands are generated when the map is evaluated but the current texture coordinates are not updated with the value of these`glTexCoord`commands. **GL_MAP2_TEXTURE_COORD_2**- Each control point is two floating-point values representing the
*s*and*t*texture coordinates. Internal`glTexCoord2`commands are generated when the map is evaluated but the current texture coordinates are not updated with the value of these`glTexCoord`commands. **GL_MAP2_TEXTURE_COORD_3**- Each control point is three floating-point values representing the
*s*,*t*, and*r*texture coordinates. Internal`glTexCoord3`commands are generated when the map is evaluated but the current texture coordinates are not updated with the value of these`glTexCoord`commands. **GL_MAP2_TEXTURE_COORD_4**- Each control point is four floating-point values representing the
*s*,*t*,*r*, and*q*texture coordinates. Internal`glTexCoord4`commands are generated when the map is evaluated but the current texture coordinates are not updated with the value of these`glTexCoord`commands.

Initially, ` GL_AUTO_NORMAL` is enabled. If

is generated if**GL_INVALID_ENUM**is not an accepted value.*target*is generated if**GL_INVALID_VALUE**is equal to*u1*, or if*u2*is equal to*v1*.*v2*is generated if either**GL_INVALID_VALUE**or*ustride*is less than the number of values in a control point.*vstride*is generated if either**GL_INVALID_VALUE**or*uorder*is less than 1 or greater than the return value of*vorder*.**GL_MAX_EVAL_ORDER**is generated if**GL_INVALID_OPERATION**`glMap2`is executed between the execution of`glBegin`and the corresponding execution of`glEnd`.