I know a similar question has already been asked. However, I have some trouble manipulating bits and can't adapt/understand the solution.
First of all I used the Interleave bits the obvious way to get myself a Morton number. I adapted it to 3D like this:
unsigned long xyz2w(unsigned int x, unsigned int y, unsigned int z)
{
unsigned long w=0;
for (int i = 0; i < sizeof(x) * CHAR_BIT; i++)
{
w |= (x & 1U << i) << i | (y & 1U << i) << (i + 1) | (z & 1U << i) << (i + 2);
}
return w;
}
(It seems to work fine but if you ever find an error, please let me know)
Now I would like to do the opposite operation. That is: extracting the 3 coordinates based on the Morton number.
Obviously, I tried to use the adapted-for-3D part of the previous SO topic, but I didn't understand how it works. That's why I am creating a new topic.
I am not looking for a high-performance code but for a clear and understandable code that works similar to the xyz2w function (ie "The obvious way").
<< (i + 1)Example implementation:
It is not efficient but I split long lines to be more easy to understand
#define MASK(x) (1ULL << (sizeof(x) * CHAR_BIT - 1))
unsigned long long xyz2w(unsigned short x, unsigned short y, unsigned short z)
{
unsigned long long w = 0;
for(unsigned short mask = MASK(x); mask; mask >>= 1)
{
w <<= 1;
w += (!!(x & mask));
w <<= 1;
w += (!!(y & mask));
w <<= 1;
w += (!!(z & mask));
}
return w;
}
void w2xyz(unsigned long long w, unsigned short *x, unsigned short *y, unsigned short *z)
{
*x = 0; *y = 0; *z = 0;
for(unsigned short bit = 0; bit < sizeof(*x) * CHAR_BIT; bit++)
{
*z += (w & 1) << bit;
w >>= 1;
*y += (w & 1) << bit;
w >>= 1;
*x += (w & 1) << bit;
w >>= 1;
}
}
int main(void)
{
unsigned short x = 0xaabb;
unsigned short y = 0x3355;
unsigned short z = 0x22ff;
unsigned long long w = xyz2w(x,y,z);
printf("w = 0x%llx, x = %hx, y = %hx, z = %hx\n", w, x, y, z);
x = 0; y = 0; z = 0;
w2xyz(w, &x, &y, &z);
printf("x = %hx, y = %hx, z = %hx\n", x, y, z);
}