Algorithm for Back Face Detection Method Visual Realism:

(a) Identify the first polygon of the solid, numbered in a counter-clockwise fashion for the viewer. Let the m_j vertices of this polygon 1 be

                                         v_i (1), v _j (2), . . . , v _j  (m _j )

(b) Set v _j (m _j + 1), v _j (1).

(c) Find k = ( x₃  - x₂ ) ( x₁ - x₂ ) + ( y₃  - y2 ) ( y₁ - y₂ ) + ( z₃  - z₂ ) , from the coordinates of the first three vertices of polygon 1. If k < 0, go to Step (a), renumbering if necessary.

(d) Start polygon loop on i = 1 to n, n being the number of polygons.

    (i) If i = 1 go to Step (e)

    (ii) Let the number of vertices for polygon i be mi, and let the vertices be

                                 v_i (1), v_i (2), . . . , v_i  (m) . Set v_i (m_i  + 1) = v_i (1) .

    (iii) Start polygon loop on j = 1 to n.

               (1) Let the number of vertices for polygon j be m_j, and let the vertices be

                       v _j (1), v _j (2), . . . , v _j  (m _j ) . Set v _j (m _j  + 1) = v _j (1) .

               (2) Compare every sequential pair of vertex numbers p and q for polygon i, with every sequential pair of vertex numbers r and s for polygon j, except for j = i.

               (3)  If p = r and q = s, a straight match, then reverse the order of all m_i vertices for polygon i. Go to Step (v).

               (4) If p = s and q = r, a reverse match, then go to Step (v).

    (iv) End loop on j.

     (v) Find k = ( x₂  - x₁ ) ( y₃  - y₁ ) - ( x₃  - x₁ ) ( y₂  - y₁ ) , from the coordinates of the first three vertices of polygon i.

     (vi) If k > 0, pass the coordinates of all mi vertices, and the edge and surface attributes of polygon i to the plot module.

 (e) End loop on i.