Why Use the Subtexture Extension?

Why Use the Subtexture Extension?

Using a subtexture is the fastest way to update only the image of a texture. When you need to redefine only the image of the texture and keep all other parameters, using subtexture is much faster than using the glTexImage*() call.

The subtexture extension is especially useful under the following circumstances:

When you're dealing with an image that doesn't fit into texture memory, you can use the extension to load only parts of the texture and replace them as appropriate.
When you're using video frames as textures, none of the common video formats (NTSC, PAL, SECAM, HD-TV, and so on) have height and width that's a power of 2. This is problematic because height and width of those dimensions is required for textures. You therefore create a NULL texture whose dimensions are larger than the video frame and then load the video frame as a subtexture.
When you're working with an animation, loading a large texture may decrease the frame rate. Instead, load several subtextures over multiple frames to maintain a high frame rate.