Mapping points in a TOP to points in a SOP

Hi - I’m trying to do some manipulations on geometry based on a TOP. How should I go about mapping my TOP to my GEO? For example, my image is grayscale/depth info, and I want the brightness (from 0 to 1) of each pixel in image to determine the Z position of any “overlapping” point in the geometry.

I can provide more info if necessary. Thanks in advance!