Let's assume you are extracting the maximum surface over a multi-frame grid object to help clarify the discussion (for me).
Extracting the maximum surface from a multi-frame object, where each frame is a grid of values, means that the resulting surface grid will be such that each node will be the maximum value across all frames being used. And each node's maximum may come from any one of the frames.
Ok... so, I'm sure you know all that.
So, to be clear... you're looking for a surface where each value is the index of the maximum across the frames. Is that right? What would you like to do with such a surface grid of frame index values (rather than a surface grid of the actual maximums)? Just curious
Kindly,
Alan