Problem 1785. Dilate a 3d object sampled on a regular grid

3d objects can be described by a set of points on a regular grid in Euclidean space. Given the n x 3 matrix m defining some number of objects on a grid with resolution res, return a matrix p that defines these objects after dilation by a single point on the grid in every direction.

Assume an "edge" connectivity scheme for dilation (i.e. each point in the grid has 18 neighbors, one for each surface of a cube and one for each edge of the cube). Any given point should appear in the output matrix once.

m = [0 0 0]; res = 1; >> p = dilate3d(m,res)

p =

    -1    -1     0
    -1     0    -1
    -1     0     0
    -1     0     1
    -1     1     0
     0    -1    -1
     0    -1     0
     0    -1     1
     0     0    -1
     0     0     0
     0     0     1
     0     1    -1
     0     1     0
     0     1     1
     1    -1     0
     1     0    -1
     1     0     0
     1     0     1
     1     1     0