glGetTexLevelParameter

NAME

glGetTexLevelParameterfv, glGetTexLevelParameteriv - return texture parameter values for a specific level of detail

C SPECIFICATION

void glGetTexLevelParameterfv(GLenum target,
                              GLint level,
                              GLenum pname,
                              GLfloat *params)
void glGetTexLevelParameteriv(GLenum target,
                              GLint level,
                              GLenum pname,
                              GLint *params)

PARAMETERS

target	Specifies the symbolic name of the target texture, either GL_TEXTURE_1D, GL_TEXTURE_2D, GL_TEXTURE_3D_EXT, GL_PROXY_TEXTURE_1D, GL_PROXY_TEXTURE_2D or GL_PROXY_TEXTURE_3D_EXT.
level	Specifies the level-of-detail number of the desired image. Level 0 is the base image level. Level n is the n^th mipmap reduction image.
pname	Specifies the symbolic name of a texture parameter. GL_TEXTURE_WIDTH, GL_TEXTURE_HEIGHT, GL_TEXTURE_DEPTH_EXT, GL_TEXTURE_INTERNAL_FORMAT, GL_TEXTURE_BORDER, GL_TEXTURE_RED_SIZE, GL_TEXTURE_GREEN_SIZE, GL_TEXTURE_BLUE_SIZE, GL_TEXTURE_ALPHA_SIZE, GL_TEXTURE_LUMINANCE_SIZE, and GL_TEXTURE_INTENSITY_SIZE are accepted.
params	Returns the requested data.

DESCRIPTION

glGetTexLevelParameter returns in params texture parameter values for a specific level-of-detail value, specified as level. target defines the target texture, either GL_TEXTURE_1D, GL_TEXTURE_2D, GL_TEXTURE_3D_EXT, GL_PROXY_TEXTURE_1D, GL_PROXY_TEXTURE_2D, or GL_PROXY_TEXTURE_3D_EXT.

GL_MAX_TEXTURE_SIZE is not really descriptive enough. It has to report the largest square texture image that can be accommodated with mipmaps and borders, but a long skinny texture, or a texture without mipmaps and borders, may easily fit in texture memory. The proxy targets allow the user to more accurately query whether the GL can accommodate a texture of a given configuration. If the texture cannot be accommodated, the texture state variables, which may be queried with glGetTexLevelParameter, are set to 0. If the texture can be accommodated, the texture state values will be set as they would be set for a non-proxy target.

pname specifies the texture parameter whose value or values will be returned.

The accepted parameter names are as follows:

GL_TEXTURE_WIDTH: params returns a single value, the width of the texture image. This value includes the border of the texture image. The initial value is 0.
GL_TEXTURE_HEIGHT: params returns a single value, the height of the texture image. This value includes the border of the texture image. The initial value is 0.
GL_TEXTURE_DEPTH_EXT: params returns a single value, the depth of the texture image. This value includes the border of the texture image. The initial value is 0.
GL_TEXTURE_INTERNAL_FORMAT: params returns a single value, the internal format of the texture image.
GL_TEXTURE_BORDER: params returns a single value, the width in pixels of the border of the texture image. The initial value is 0.
GL_TEXTURE_RED_SIZE,
GL_TEXTURE_GREEN_SIZE,
GL_TEXTURE_BLUE_SIZE,
GL_TEXTURE_ALPHA_SIZE,
GL_TEXTURE_LUMINANCE_SIZE,
GL_TEXTURE_INTENSITY_SIZE: The internal storage resolution of an individual component. The resolution chosen by the GL will be a close match for the resolution requested by the user with the component argument of glTexImage1D, glTexImage2D, and glTexImage3DEXT. The initial value is 0.

NOTES

If an error is generated, no change is made to the contents of params.

GL_TEXTURE_INTERNAL_FORMAT is only available if the GL version is 1.1 or greater. In version 1.0, use GL_TEXTURE_COMPONENTS instead.

GL_PROXY_TEXTURE_1D and GL_PROXY_TEXTURE_2D are only available if the GL version is 1.1 or greater.

EXTENSIONS

Some routines and constants for this function are part of an extension, not part of the core GL command set. The following extension names must be present in the string returned by glGetString when called with argument GL_EXTENSIONS to use these routines and constants.

GL_EXT_texture3D: GL_TEXTURE_3D_EXT, GL_PROXY_TEXTURE_3D_EXT, and GL_TEXTURE_DEPTH_EXT are part of the EXT_texture3D extension.

ERRORS

GL_INVALID_ENUM is generated if target or pname is not an accepted value.

GL_INVALID_VALUE is generated if level is less than 0.

GL_INVALID_VALUE may be generated if level is greater than log max, where max is the returned value of GL_MAX_TEXTURE_SIZE.

GL_INVALID_OPERATION is generated if glGetTexLevelParameter is executed between the execution of glBegin and the corresponding execution of glEnd.