glEvalCoord2fv function

The glEvalCoord2fv function evaluates enabled two-dimensional maps.

Syntax


void WINAPI glEvalCoord2fv(
   const GLfloat *u
);

Parameters

u

A pointer to an array containing the domain coordinate u.

Return value

This function does not return a value.

Remarks

The glEvalCoord2fv function evaluates enabled two-dimensional maps using two domain values, u and v. Define maps with glMap1. Enable or disable them with glEnable and glDisable.

When one of the glEvalCoord functions is issued, all currently enabled maps of the indicated dimension are evaluated. Then, for each enabled map, it is as if the corresponding OpenGL function were issued with the computed value. That is, if GL_MAP1_INDEX or GL_MAP2_INDEX is enabled, a glIndex function is simulated. If GL_MAP1_COLOR_4 or GL_MAP2_COLOR_4 is enabled, a glcolor function is simulated. If GL_MAP1_NORMAL or GL_MAP2_NORMAL is enabled, a normal vector is produced, and if any of GL_MAP1_TEXTURE_COORD_1, GL_MAP1_TEXTURE_COORD_2, GL_MAP1_TEXTURE_COORD_3, GL_MAP1_TEXTURE_COORD_4, GL_MAP2_TEXTURE_COORD_1, GL_MAP2_TEXTURE_COORD_2, GL_MAP2_TEXTURE_COORD_3, and GL_MAP2_TEXTURE_COORD_4 is enabled, then an appropriate glTexCoord function is simulated.

OpenGL uses evaluated values instead of current values for those evaluations that are enabled, and current values otherwise, for color, color index, normal, and texture coordinates. However, the evaluated values do not update the current values. Thus, if glVertex functions are interspersed with glEvalCoord functions, the color, normal, and texture coordinates associated with the glVertex functions are not affected by the values generated by the glEvalCoord functions, but only by the most recent glColor, glIndex, glNormal, and glTexCoord functions.

If automatic normal generation is enabled, glEvalCoord2fv calls glEnable with argument GL_AUTO_NORMAL to generate surface normals analytically, regardless of the contents or enabling of the GL_MAP2_NORMAL map. Let

Dd373526.evlcrd01(en-us,VS.85).png

The generated normal n is

Dd373526.evlcrd02(en-us,VS.85).png

The following functions retrieve information related to the glEvalCoord2fv function:

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

glIsEnabled with argument GL_MAP2_VERTEX_3

glIsEnabled with argument GL_MAP2_VERTEX_4

glIsEnabled with argument GL_MAP2_INDEX

glIsEnabled with argument GL_MAP2_COLOR_4

glIsEnabled with argument GL_MAP2_NORMAL

glIsEnabled with argument GL_MAP2_TEXTURE_COORD_1

glIsEnabled with argument GL_MAP2_TEXTURE_COORD_2

glIsEnabled with argument GL_MAP2_TEXTURE_COORD_3

glIsEnabled with argument GL_MAP2_TEXTURE_COORD_4

glIsEnabled with argument GL_AUTO_NORMAL

Requirements

Minimum supported client

Windows 2000 Professional [desktop apps only]

Minimum supported server

Windows 2000 Server [desktop apps only]

Header

Gl.h

Library

Opengl32.lib

DLL

Opengl32.dll

See also

glBegin
glColor
glDisable
glEnable
glEnd
glEvalMesh
glEvalPoint
glGetMap
glIndex
glIsEnabled
glMap1
glMap2
glMapGrid
glNormal
glTexCoord
glVertex

 

 

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