glTexGen — control the generation of texture coordinates
void glTexGeni( | GLenum | coord, |
GLenum | pname, | |
GLint | param) ; |
void glTexGenf( | GLenum | coord, |
GLenum | pname, | |
GLfloat | param) ; |
void glTexGend( | GLenum | coord, |
GLenum | pname, | |
GLdouble | param) ; |
coord
Specifies a texture coordinate.
Must be one of GL_S
, GL_T
, GL_R
, or GL_Q
.
pname
Specifies the symbolic name of the texture-coordinate generation function.
Must be GL_TEXTURE_GEN_MODE
.
param
Specifies a single-valued texture generation parameter,
one of GL_OBJECT_LINEAR
, GL_EYE_LINEAR
, GL_SPHERE_MAP
,
GL_NORMAL_MAP
, or GL_REFLECTION_MAP
.
void glTexGeniv( | GLenum | coord, |
GLenum | pname, | |
const GLint * | params) ; |
void glTexGenfv( | GLenum | coord, |
GLenum | pname, | |
const GLfloat * | params) ; |
void glTexGendv( | GLenum | coord, |
GLenum | pname, | |
const GLdouble * | params) ; |
coord
Specifies a texture coordinate.
Must be one of GL_S
, GL_T
, GL_R
, or GL_Q
.
pname
Specifies the symbolic name of the texture-coordinate generation function
or function parameters.
Must be
GL_TEXTURE_GEN_MODE
,
GL_OBJECT_PLANE
, or
GL_EYE_PLANE
.
params
Specifies a pointer to an array of texture generation parameters.
If pname
is GL_TEXTURE_GEN_MODE
,
then the array must contain a single symbolic constant,
one of
GL_OBJECT_LINEAR
,
GL_EYE_LINEAR
,
GL_SPHERE_MAP
,
GL_NORMAL_MAP
, or
GL_REFLECTION_MAP
.
Otherwise,
params
holds the coefficients for the texture-coordinate generation function
specified by pname
.
glTexGen
selects a texture-coordinate generation function
or supplies coefficients for one of the functions.
coord
names one of the (s, t, r, q) texture
coordinates; it must be one of the symbols
GL_S
,
GL_T
,
GL_R
, or
GL_Q
.
pname
must be one of three symbolic constants:
GL_TEXTURE_GEN_MODE
,
GL_OBJECT_PLANE
, or
GL_EYE_PLANE
.
If pname
is GL_TEXTURE_GEN_MODE
,
then params
chooses a mode,
one of
GL_OBJECT_LINEAR
,
GL_EYE_LINEAR
,
GL_SPHERE_MAP
,
GL_NORMAL_MAP
, or
GL_REFLECTION_MAP
.
If pname
is either GL_OBJECT_PLANE
or GL_EYE_PLANE
,
params
contains coefficients for the corresponding
texture generation function.
If the texture generation function is GL_OBJECT_LINEAR
,
the function
is used, where
coord
,
params
, and
GL_OBJECT_LINEAR
coordinate generation function as its distance from sea level;
that altitude can then be used to index the texture image to map white snow
onto peaks and green grass onto foothills.
If the texture generation function is GL_EYE_LINEAR
, the function
is used, where
and
params
, and
glTexGen
is invoked.
If
Note that the values in params
define a reference plane in eye coordinates.
The modelview matrix that is applied to them may not be the same one
in effect when the polygon vertices are transformed.
This function establishes a field of texture coordinates
that can produce dynamic contour lines on moving objects.
If the texture generation function is GL_SPHERE_MAP
and coord
is either
GL_S
or
GL_T
,
Finally, let
To enable or disable a texture-coordinate generation function, call
glEnable or glDisable
with one of the symbolic texture-coordinate names
(GL_TEXTURE_GEN_S
,
GL_TEXTURE_GEN_T
,
GL_TEXTURE_GEN_R
, or
GL_TEXTURE_GEN_Q
) as the argument.
When enabled,
the specified texture coordinate is computed
according to the generating function associated with that coordinate.
When disabled,
subsequent vertices take the specified texture coordinate
from the current set of texture coordinates. Initially, all texture
generation functions are set to GL_EYE_LINEAR
and are disabled.
Both
When the ARB_multitexture
extension is supported, glTexGen
sets the
texture generation parameters for the currently active texture unit,
selected with glActiveTexture.
GL_INVALID_ENUM
is generated when coord
or pname
is not an
accepted defined value,
or when pname
is GL_TEXTURE_GEN_MODE
and params
is not an
accepted defined value.
GL_INVALID_ENUM
is generated when pname
is GL_TEXTURE_GEN_MODE
,
params
is GL_SPHERE_MAP
,
and coord
is either GL_R
or GL_Q
.
GL_INVALID_OPERATION
is generated if glTexGen
is executed between the execution of glBegin
and the corresponding execution of glEnd.
glIsEnabled with argument GL_TEXTURE_GEN_S
glIsEnabled with argument GL_TEXTURE_GEN_T
glIsEnabled with argument GL_TEXTURE_GEN_R
glIsEnabled with argument GL_TEXTURE_GEN_Q
glActiveTexture, glCopyPixels, glCopyTexImage2D, glCopyTexSubImage1D, glCopyTexSubImage2D, glCopyTexSubImage3D, glTexEnv, glTexImage1D, glTexImage2D, glTexImage3D, glTexParameter, glTexSubImage1D, glTexSubImage2D, glTexSubImage3D
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/.