2D texture processing/evaluation

Hi folks,

I combined a set of 2D textures in a single 2D texture. Now, I am in need to determine the sum of all the texture elements of this “result” texture.

Does anybody know a method to calculate the sum of this 2D texture without copying it to the main memory ?

Since I have no experiences with register combiners or other extensions, is this maybe a possible way for the calculation ?

E.g. calculating the sum of the 2D texture along a row or column into a 1D texture (which could be copied to the main memory, since it is smaller) ??? *<:-)

Any help or hint is greatly appreciated