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GLMAP1(3G)			 OpenGL Manual			    GLMAP1(3G)

NAME
       glMap1 - define a one-dimensional evaluator

C SPECIFICATION
       void glMap1f(GLenum target, GLfloat u1, GLfloat u2, GLint stride,
		    GLint order, const GLfloat * points);

       void glMap1d(GLenum target, GLdouble u1, GLdouble u2, GLint stride,
		    GLint order, const GLdouble * points);

PARAMETERS
       target
	   Specifies the kind of values that are generated by the evaluator.
	   Symbolic constants GL_MAP1_VERTEX_3, GL_MAP1_VERTEX_4,
	   GL_MAP1_INDEX, GL_MAP1_COLOR_4, GL_MAP1_NORMAL,
	   GL_MAP1_TEXTURE_COORD_1, GL_MAP1_TEXTURE_COORD_2,
	   GL_MAP1_TEXTURE_COORD_3, and GL_MAP1_TEXTURE_COORD_4 are accepted.

       u1, u2
	   Specify a linear mapping of u, as presented to glEvalCoord1(), to
	   u^, the variable that is evaluated by the equations specified by
	   this command.

       stride
	   Specifies the number of floats or doubles between the beginning of
	   one control point and the beginning of the next one in the data
	   structure referenced in points. 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.

       order
	   Specifies the number of control points. Must be positive.

       points
	   Specifies a pointer to the array of control points.

DESCRIPTION
       Evaluators provide a way to use polynomial or rational polynomial
       mapping to produce vertices, normals, texture coordinates, and colors.
       The values produced by an evaluator are sent to further stages of GL
       processing just as if they had been presented using glVertex(),
       glNormal(), glTexCoord(), and glColor() commands, except that the
       generated values do not update the current normal, texture coordinates,
       or color.

       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 splines used in computer
       graphics: B-splines, Bezier curves, Hermite splines, and so on.

       Evaluators define curves based on Bernstein polynomials. Define p ⁡ u^
       as

       p ⁡ u^ = Σ i = 0 n B i n ⁡ u^ ⁢ R i

       where R i is a control point and B i n ⁡ u^ is the ith Bernstein
       polynomial of degree n (order = n + 1):

       B i n ⁡ u^ = n i ⁢ u^ i ⁢ 1 - u^ n - i

       Recall that

       0 0 == 1 and n 0 == 1

       glMap1 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.  glEvalCoord1() evaluates
       the one-dimensional maps that are enabled. When glEvalCoord1() presents
       a value u, the Bernstein functions are evaluated using u^, where u^ = u
       - u1 u2 - u1

       target is a symbolic constant that indicates what kind of control
       points are provided in points, and what output is generated when the
       map is evaluated. It can assume one of nine predefined values:

       GL_MAP1_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_MAP1_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_MAP1_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_MAP1_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_MAP1_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_MAP1_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_MAP1_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_MAP1_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_MAP1_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.

       stride, order, and points define the array addressing for accessing the
       control points.	points is the location of the first control point,
       which occupies one, two, three, or four contiguous memory locations,
       depending on which map is being defined.	 order is the number of
       control points in the array.  stride specifies how many float or double
       locations to advance the internal memory pointer to reach the next
       control point.

NOTES
       As is the case with all GL commands that accept pointers to data, it is
       as if the contents of points were copied by glMap1 before glMap1
       returns. Changes to the contents of points have no effect after glMap1
       is called.

ERRORS
       GL_INVALID_ENUM is generated if target is not an accepted value.

       GL_INVALID_VALUE is generated if u1 is equal to u2.

       GL_INVALID_VALUE is generated if stride is less than the number of
       values in a control point.

       GL_INVALID_VALUE is generated if order is less than 1 or greater than
       the return value of GL_MAX_EVAL_ORDER.

       GL_INVALID_OPERATION is generated if glMap1 is executed between the
       execution of glBegin() and the corresponding execution of glEnd().

       GL_INVALID_OPERATION is generated if glMap1 is called and the value of
       GL_ACTIVE_TEXTURE is not GL_TEXTURE0.

ASSOCIATED GETS
       glGetMap()

       glGet() with argument GL_MAX_EVAL_ORDER

       glIsEnabled() with argument GL_MAP1_VERTEX_3

       glIsEnabled() with argument GL_MAP1_VERTEX_4

       glIsEnabled() with argument GL_MAP1_INDEX

       glIsEnabled() with argument GL_MAP1_COLOR_4

       glIsEnabled() with argument GL_MAP1_NORMAL

       glIsEnabled() with argument GL_MAP1_TEXTURE_COORD_1

       glIsEnabled() with argument GL_MAP1_TEXTURE_COORD_2

       glIsEnabled() with argument GL_MAP1_TEXTURE_COORD_3

       glIsEnabled() with argument GL_MAP1_TEXTURE_COORD_4

SEE ALSO
       glBegin(), glColor(), glEnable(), glEvalCoord(), glEvalMesh(),
       glEvalPoint(), glMap2(), glMapGrid(), glNormal(), glTexCoord(),
       glVertex()

COPYRIGHT
       Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
       under the SGI Free Software B License. For details, see
       http://oss.sgi.com/projects/FreeB/.

AUTHORS
       opengl.org

opengl.org			  03/16/2013			    GLMAP1(3G)
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