Someone can correct me, but I don't believe it is possible to compute the high quality gradients without doing more texture samples. I think what is being said in the article is that the same procedure for calculating the pixel value can be used to calculate the gradients, but they are separate processes. Under this model, there are 8 texture samples for the pixel value, and 8 samples each for the 3 cardinal directions. An extra 24 texture samples isn't as great as I would have hoped, but the gradient does look better than when it is computed using central differencing.
rtclawsonMember Since 16 Jan 2013
Offline Last Active Oct 22 2013 10:58 AM