GLdouble u1,
GLdouble u )
void GLAPIENTRY glMap1f( GLenum target,
GLfloat u1,
GLfloat u )
PARAMETERS
target Specifies the kind of values that are generated by the evalua‐
tor. 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 ac‐
cepted.
u1, u Specify a linear mapping of u, as presented to glEvalCoord1, to
u, the variable that is evaluated by the equations specified by
this command.
_param4 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 _param6. 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.
_param5 Specifies the number of control points. Must be positive.
_param6 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, 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 us‐
ing 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)=iΣ0Bi(u)Ri
where Ri is a control point and Bi(u) is the ith Bernstein polynomial of
degree n (_param5 = n+1):
Bi(u)=⎝n⎠ui(1−u)n−i
i
Recall that
target is a symbolic constant that indicates what kind of control points
are provided in _param6, 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 val‐
ues 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 val‐
ues 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 val‐
ues 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 val‐
ues 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 coordi‐
nates 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 coordi‐
nates are not updated with the value of these
glTexCoord commands.
GL_MAP1_TEXTURE_COORD_3 Each control point is three floating-point val‐
ues representing the s, t, and r texture coor‐
the control points. _param6 is the location of the first control point,
which occupies one, two, three, or four contiguous memory locations, de‐
pending on which map is being defined. _param5 is the number of control
points in the array. _param4 specifies how many float or double loca‐
tions 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 _param6 were copied by glMap1 before glMap1 re‐
turns. Changes to the contents of _param6 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 u.
GL_INVALID_VALUE is generated if _param4 is less than the number of val‐
ues in a control point.
GL_INVALID_VALUE is generated if _param5 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 exe‐
cution of glBegin and the corresponding execution of glEnd.
When the GL_ARB_multitexture extension is supported,
GL_INVALID_OPERATION is generated if glMap1 is called and the value of
GL_ACTIVE_TEXTURE_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, glColor, glEnable, glEvalCoord, glEvalMesh, glEvalPoint,
glMap2, glMapGrid, glNormal, glTexCoord, glVertex
GLMAP1(3G)
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