Using 3D Textures

The extension also provides the following additional features:

• Pixel storage modes. The extension extends the pixel storage modes by adding four new state variables:

  • GL_(UN)PACK_IMAGE_HEIGHT_EXT defines the height of the image the texture is read from, analogous to the GL_(UN)PACK_LENGTH variable for image width.

  • GL_(UN)PACK_SKIP_IMAGES_EXT determines an initial skip analogous to GL_(UN)PACK_SKIP_PIXELS and GL_(UN)PACK_SKIP_LINES.

    All four default to zero.

• Texture wrap modes. The functions glTexParameter*(), accept the additional token value GL_TEXTURE_WRAP_R_EXT.

  It affects the R coordinate in the same way that GL_TEXTURE_WRAP_S affects the S coordinate and GL_TEXTURE_WRAP_T affects the T coordinate. The default value is GL_REPEAT.

• Mipmapping. Mipmapping for two-dimensional textures is discussed in the section "Multiple Levels of Detail," in Chapter 9, "Texture Mapping," of the OpenGL Programming Guide. Mipmapping for 3D textures works the same way: A 3D mipmap is an ordered set of arrays representing the same image; each array has a resolution lower than the previous one. The filtering options GL_NEAREST_MIPMAP_NEAREST, GL_NEAREST_MIPMAP_LINEAR, GL_LINEAR_MIPMAP_NEAREST, and GL_LINEAR_MIPMAP_LINEAR apply to subvolumes instead of texels.

• Proxy textures. Use the proxy texture GL_PROXY_TEXTURE_3D_EXT to query an implementation's maximum configuration. For more information on proxy textures, see "The Texture Extension Proxy Mechanism".

• Querying. Use the following call to query the 3D texture:

  glGetTexImage(GL_TEXTURE_3D_EXT)

• Subvolumes of the 3D texture can be replaced using glTexSubImage3DEXT() and glCopyTexSubImage3DEXT() (see "The Subtexture Extension").