Consider, if you will, this image:
Assuming that the four corners there have n value, I'm looking for a way to determine the best values for the red dots (or, actually, and point within the square). I'm trying to determine light values at a finer grain than just finding the nearest corner and using it.
Is there a way to do this? I tried simple linear interpolation combining both directions, but the results aren't satisfactory, so I think the way I thought up is fatally flawed.
Thanks for any help!