C SPECIFICATION

void glTexStorage2D(GLenum target, GLsizei levels, GLenum internalformat, GLsizei width, GLsizei height);

PARAMETERS

target

Specify the target of the operation. target must be one of GL_TEXTURE_2D, GL_PROXY_TEXTURE_2D, GL_TEXTURE_1D_ARRAY, GL_PROXY_TEXTURE_1D_ARRAY, GL_TEXTURE_RECTANGLE, GL_PROXY_TEXTURE_RECTANGLE, or GL_PROXY_TEXTURE_CUBE_MAP.

levels

Specify the number of texture levels.

internalformat

Specifies the sized internal format to be used to store texture image data.

width

Specifies the width of the texture, in texels.

height

Specifies the height of the texture, in texels.

DESCRIPTION

glTexStorage2D specifies the storage requirements for all levels of a two-dimensional texture or one-dimensional texture array simultaneously. Once a texture is specified with this command, the format and dimensions of all levels become immutable unless it is a proxy texture. The contents of the image may still be modified, however, its storage requirements may not change. Such a texture is referred to as an immutable-format texture.

The behavior of glTexStorage2D depends on the target parameter. When target is GL_TEXTURE_2D, GL_PROXY_TEXTURE_2D, GL_TEXTURE_RECTANGLE, GL_PROXY_TEXTURE_RECTANGLE or GL_PROXY_TEXTURE_CUBE_MAP, calling glTexStorage2D is equivalent, assuming no errors are generated, to executing the following pseudo-code:

    for (i = 0; i < levels; i++)
    {
        glTexImage2D(target, i, internalformat, width, height, 0, format, type, NULL);
        width = max(1, (width / 2));
        height = max(1, (height / 2));
    }

When target is GL_TEXTURE_CUBE_MAP, glTexStorage2D is equivalent to:

    for (i = 0; i < levels; i++)
    {
        for (face in (+X, -X, +Y, -Y, +Z, -Z))
        {
            glTexImage2D(face, i, internalformat, width, height, 0, format, type, NULL);
        }
        width = max(1, (width / 2));
        height = max(1, (height / 2));
    }

When target is GL_TEXTURE_1D or GL_TEXTURE_1D_ARRAY, glTexStorage2D is equivalent to:

    for (i = 0; i < levels; i++)
    {
        glTexImage2D(target, i, internalformat, width, height, 0, format, type, NULL);
        width = max(1, (width / 2));
    }

Since no texture data is actually provided, the values used in the pseudo-code for format and type are irrelevant and may be considered to be any values that are legal for the chosen internalformat enumerant. internalformat must be one of the sized internal formats given in Table 1 below, one of the sized depth-component formats GL_DEPTH_COMPONENT32F, GL_DEPTH_COMPONENT24, or GL_DEPTH_COMPONENT16, or one of the combined depth-stencil formats, GL_DEPTH32F_STENCIL8, or GL_DEPTH24_STENCIL8. Upon success, the value of GL_TEXTURE_IMMUTABLE_FORMAT becomes GL_TRUE. The value of GL_TEXTURE_IMMUTABLE_FORMAT may be discovered by calling glGetTexParameter() with pname set to GL_TEXTURE_IMMUTABLE_FORMAT. No further changes to the dimensions or format of the texture object may be made. Using any command that might alter the dimensions or format of the texture object (such as glTexImage2D() or another call to glTexStorage2D) will result in the generation of a GL_INVALID_OPERATION error, even if it would not, in fact, alter the dimensions or format of the object.

Table 1. Sized Internal Formats

COPYRIGHT

Copyright © 2011 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. m[blue]http://opencontent.org/openpub/m[].