GLGETTEXLEVELPARAMET(3G)

NAME
glGetTexLevelParameter - 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, GL_PROXY_TEXTURE_1D, GL_PROXY_TEXTURE_2D, GL_PROXY_TEXTURE_3D, GL_TEXTURE_CUBE_MAP_POSITIVE_X, GL_TEXTURE_CUBE_MAP_NEGATIVE_X, GL_TEXTURE_CUBE_MAP_POSITIVE_Y, GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, GL_TEXTURE_CUBE_MAP_POSITIVE_Z, GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, or GL_PROXY_TEXTURE_CUBE_MAP.

level
    Specifies the level-of-detail number of the desired image. Level 0 is the base image level. Level n is the nth mipmap reduction image.

pname
    Specifies the symbolic name of a texture parameter. GL_TEXTURE_WIDTH, GL_TEXTURE_HEIGHT, GL_TEXTURE_DEPTH, 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, GL_TEXTURE_INTENSITY_SIZE, GL_TEXTURE_DEPTH_SIZE, GL_TEXTURE_COMPRESSED, and GL_TEXTURE_COMPRESSED_IMAGE_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, GL_PROXY_TEXTURE_1D, GL_PROXY_TEXTURE_2D, GL_PROXY_TEXTURE_3D, GL_TEXTURE_CUBE_MAP_POSITIVE_X, GL_TEXTURE_CUBE_MAP_NEGATIVE_X, GL_TEXTURE_CUBE_MAP_POSITIVE_Y, GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, GL_TEXTURE_CUBE_MAP_POSITIVE_Z, GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, or GL_PROXY_TEXTURE_CUBE_MAP.

GL_MAX_TEXTURE_SIZE, and GL_MAX_3D_TEXTURE_SIZE are 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

    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,

GL_TEXTURE_DEPTH_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(), glTexImage3D(), glCopyTexImage1D(), and glCopyTexImage2D(). The initial value is 0.

GL_TEXTURE_COMPRESSED

    params returns a single boolean value indicating if the texture image is stored in a compressed internal format. The initiali value is GL_FALSE.

GL_TEXTURE_COMPRESSED_IMAGE_SIZE

    params returns a single integer value, the number of unsigned bytes of the compressed texture image that would be returned from glGetCompressedTexImage().

NOTES

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

GL_TEXTURE_INTERNAL_FORMAT is available only 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 available only if the GL version is 1.1 or greater.

GL_TEXTURE_3D, GL_PROXY_TEXTURE_3D, and GL_TEXTURE_DEPTH are available only if the GL version is 1.2 or greater.

GL_TEXTURE_COMPRESSED, GL_TEXTURE_COMPRESSED_IMAGE_SIZE, GL_TEXTURE_CUBE_MAP_POSITIVE_X, GL_TEXTURE_CUBE_MAP_NEGATIVE_X, GL_TEXTURE_CUBE_MAP_POSITIVE_Y, GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, GL_TEXTURE_CUBE_MAP_POSITIVE_Z, GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, and GL_PROXY_TEXTURE_CUBE_MAP are available only if the GL version is 1.3 or greater.

For OpenGL versions 1.3 and greater, or when the ARB_multitexture extension is supported, glGetTexLevelParameter returns the texture level parameters for the active texture unit.

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 2 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().

GL_INVALID_OPERATION is generated if GL_TEXTURE_COMPRESSED_IMAGE_SIZE is queried on texture images with an uncompressed internal format or on proxy targets.

SEE ALSO

glActiveTexture(), glGetTexParameter(), glCopyTexImage1D(), glCopyTexImage2D(), glCopyTexSubImage1D(), glCopyTexSubImage2D(), glCopyTexSubImage3D(), glTexEnv(), glTexGen(), glTexImage1D(), glTexImage2D(), glTexImage3D(), glTexSubImage1D(), glTexSubImage2D(), glTexSubImage3D(), glTexParameter()

COPYRIGHT

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/.