Figure 3.

a: 2D example of a marker triangle in space. Projection peaks along the two axes are back projected and the triangle with minimum side distance (d_i) change from the initial reference side distances (dref_i) is identified as a solution. b. Example of coordinate swapping during backprojection (y coordinate swapped between green and blue markers) leading to an erroneous reflected triangle (in bold) being identified as the initial solution instead of the correct triangle (dotted). Direction of the triangle normal represented by a ✖ for going into and • for coming out of the plane is however reversed allowing for rejection of this solution. Triangle in gray shows an example of a triangle from among the 2925 triangles, which is not in the subset of 36 possible triangles as it misses at least one projection.