How to compute a 3D Morton number (interleave the bits of 3 ints)

Question

I\'m looking for a fast way to compute a 3D Morton number. This site has a magic-number based trick for doing it for 2D Morton numbers, but it doesn\'t seem obvious how to e

Answer 1

Following is the code snippet to generate Morton key of size 64 bits for 3-D point.

using namespace std;

unsigned long long spreadBits(unsigned long long x)
{
    x=(x|(x<<20))&0x000001FFC00003FF;
    x=(x|(x<<10))&0x0007E007C00F801F;
    x=(x|(x<<4))&0x00786070C0E181C3;
    x=(x|(x<<2))&0x0199219243248649;
    x=(x|(x<<2))&0x0649249249249249;
    x=(x|(x<<2))&0x1249249249249249;
    return x;
}

int main()
{
    unsigned long long x,y,z,con=1;
    con=con<<63;
    printf("%#llx\n",(spreadBits(x)|(spreadBits(y)<<1)|(spreadBits(z)<<2))|con);    
}