Sometimes it's useful to only change a portion of a texture at a time.
This is accomplished using the function glTexSubImage2D().
| Base texture (glTexImage2D) | Sub texture (glTexSubImage2D) | Result | |
|---|---|---|---|
|
| | ==> |
|
One use of subloading is when the size of the texture image is not a power of 2; subloading avoids the need to resize the image data before using it.
One can create a base texture with a size that is a power of 2, subload the real image data into a portion of the full texture, and then assign appropriate texture coordinates so that only the desired portion of the texture is seen.
| 
|
| texture coordinates (0, 0) - (1, 1) | texture coordinates (0, 0) - (0.625, 0.9375) |
I have added a new function to the dms::Texture2D class - subload() -
for this feature.
To use it, assign an initial image to the texture & call define().
Then, you can later assign a different image to the texture and call
subload(). Make sure that the new, subloaded image is no larger
than the original image.
Example: subload.cpp