glMap1

NAME

C SPECIFICATION

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

DESCRIPTION

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(û) as

p(û) = SUM( Bⁿ_i(û)R_i )

where R_i is a control point and Bⁿ_i(û) is the i^th Bernstein polynomial of degree n (order = n+1):

Bⁿ_i(û) = (ⁿ_i) ûⁱ (1 - û)^{n - i}

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 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

û = (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.

NOTES

ERRORS

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.

ASSOCIATED GETS

SEE ALSO