glCompressedTextureSubImage2D

glCompressedTexSubImage2D: man4/glCompressedTexSubImage2D.xml

Texturing allows elements of an image array to be read by shaders. glCompressedTexSubImage2D and glCompressedTextureSubImage2D redefine a contiguous subregion of an existing two-dimensional texture image. The texels referenced by data replace the portion of the existing texture array with x indices xoffset and xoffset + width - 1, and the y indices yoffset and yoffset + height - 1, inclusive. This region may not include any texels outside the range of the texture array as it was originally specified. It is not an error to specify a subtexture with width of 0, but such a specification has no effect. internalformat must be a known compressed image format (such as GL_RGTC ) or an extension-specified compressed-texture format. The format of the compressed texture image is selected by the GL implementation that compressed it (see glTexImage2D ) and should be queried at the time the texture was compressed with glGetTexLevelParameter. If a non-zero named buffer object is bound to the GL_PIXEL_UNPACK_BUFFER target (see glBindBuffer ) while a texture image is specified, data is treated as a byte offset into the buffer object's data store.