this is my first question on these forums : )
I'm writing a coordinate class in Java for a spatial octree voxel system. These coordinates are not floating point coordinates, they are 4D integer indexes into the octree (3 normal dimensions X, Y, Z, and a forth for depth into the tree). The first 3 values are all shorts, the last dimension is a byte. In actual use right now only the first 11 bits of the shorts are used and only 3 bits of the byte, but this could be subject to change.
Now I'm trying to write a 'good' hash function for this class. The problem I'm wrestling with is that the coordinates are often going to be used in highly spatial coherent situations (hope I'm using the right terminology there). What I mean is that often times a coordinate will be hashed along with its immediately adjacent neighbors and other nearby coordinates.
Is there an effective practice to cause these 'near to each other' coordinates to produce significantly different hashcodes?