Masking in OpenGL ES

Answer 1

For the technique from the NeHe tutorial to work correctly, the background of your source image (i.e. anywhere where the mask image is white) needs to be full black. Although it’s not obvious from your first image exactly what the source is, I suspect that it isn’t black in the places that are brightening in the final image.

However, doing masking this way isn’t necessary in OpenGL ES 1.1. You can render an image with an alpha mask in a single pass using multitexturing. Furthermore, if your mask and your image are always drawn together, you’re better off just baking them into a single RGBA texture—no multitexturing required.

Answer 2

i have two images which are overlapping on each other.(the way in which cards are placed on top of each other)

now if i move my finger over the top most image that portion of the image should become transparent.(opacity of that part should become 0).

i am new to OpenGL ES development.

kindly help me out or give me any suggestion to complete this functionality.

Thanks in advance