BUGFIX-66

Bug 20: Mangled Morton Space-Filling Curve

This code interleaves the bits of the components of an (x, y, z) coordinate.
It assumes that x fits in 11 bits, y fits in 11 bits, and z fits in 10 bits.
This interleaving maps 3D space onto 1D space while tending to preserve point proximity.
If two points are nearby in 3D space they tend to be nearby in the linearization.

Fix The Tiny Bug In This Go Code:

func morton(x, y, z uint32) uint32 { const ( shift1 = 12 mask1 = 0b_0000_0000_0111_1100_0000_0000_0011_1111 ) z = (z<<shift1 + z) & mask1 y = (y<<shift1 + y) & mask1 x = (x<<shift1 + x) & mask1 const ( shift2 = 6 mask2 = 0b_0001_1000_0001_1100_0000_1110_0000_0111 ) z = (z<<shift2 + z) & mask2 y = (y<<shift2 + y) & mask2 x = (x<<shift2 + x) & mask2 const ( shift3 = 3 mask3 = 0b_0001_1001_0000_1100_1000_0110_0100_0011 ) z = (z<<shift3 + z) & mask3 y = (y<<shift3 + y) & mask3 x = (x<<shift3 + x) & mask3 const ( shift4 = 2 mask4 = 0b_0100_1001_0010_0100_1001_0010_0100_1001 ) z = (z<<shift4 + z) & mask4 y = (y<<shift4 + y) & mask4 x = (x<<shift4 + x) & mask4 return z<<2 + y<<1 + x }

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