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glMap1(3G)							    glMap1(3G)

NAME
       glMap1, glMap1d, glMap1f - define a one-dimensional evaluator

SYNOPSIS
       void glMap1d(
	       GLenum target,
	       GLdouble u1,
	       GLdouble u2,
	       GLint stride,
	       GLint order,
	       const GLdouble *points ); void glMap1f(
	       GLenum target,
	       GLfloat u1,
	       GLfloat u2,
	       GLint stride,
	       GLint order,
	       const GLfloat *points );

PARAMETERS
       Specifies  the kind of values that are generated by the evaluator. Sym‐
       bolic  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_TEX‐
       TURE_COORD_2, GL_MAP1_TEXTURE_COORD_3, and GL_MAP1_TEXTURE_COORD_4  are
       accepted.   Specify  a  linear  mapping of u, as presented to glEvalCo‐
       ord1(), to u hat, the variable that is evaluated by the equations spec‐
       ified  by  this	command.   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 con‐
       trol points to be embedded in arbitrary data structures. The only  con‐
       straint	is  that the values for a particular control point must occupy
       contiguous memory locations.  Specifies the number of  control  points.
       Must be positive.  Specifies a pointer to the array of control points.

DESCRIPTION
       Evaluators  provide a way to use polynomial or rational polynomial map‐
       ping to produce vertices, normals, texture coordinates, and colors. The
       values  produced	 by an evaluator are sent to further stages of GL pro‐
       cessing just as if they had been	 presented  using  glVertex(),	glNor‐
       mal(),  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
       hat )  as p ( u hat ) { sum from i=0 to n } B[i] sup n ( u hat ) R[i]

       where R[i] is a control point and B[i] sup n ( u hat ) is the ith Bern‐
       stein  polynomial of degree n (order = n + 1): B[i] sup n ( u hat ) { n
       above i }} u hat sup i ( 1 - u hat ) sup { n - i }

       Recall that 0 sup 0 == 1 { n above 0 }}	right ) == 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 call‐
       ing glEnable() and glDisable() with the map name, one of the nine  pre‐
       defined	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 hat, where u
       hat = {u - "u1"} over {"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:  Each
       control	point is three floating-point values representing x, y, and z.
       Internal glVertex3() commands are generated when the map is  evaluated.
       Each  control point is four floating-point values representing x, y, z,
       and w.  Internal glVertex4() commands are generated  when  the  map  is
       evaluated.   Each control point is a single floating-point value repre‐
       senting 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.  Each control point is  four	float‐
       ing-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() com‐
       mands.  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.  Each con‐
       trol 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.  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.	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.	Each control point is four floating-point val‐
       ues 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  con‐
       trol  points  in	 the array.  stride specifies how many float or double
       locations to advance the internal memory pointer to reach the next con‐
       trol 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 val‐
       ues 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().

       When  the GL_ARB_multitexture extension is supported, GL_INVALID_OPERA‐
       TION is generated if glMap1() is called and the value of GL_ACTIVE_TEX‐
       TURE_ARB is not GL_TEXTURE0_ARB.

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(3),  glColor(3),	 glEnable(3),  glEvalCoord(3),	glEvalMesh(3),
       glEvalPoint(3), glMap2(3),  glMapGrid(3),  glNormal(3),	glTexCoord(3),
       glVertex(3)

								    glMap1(3G)
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