l defines the direction of the "light source" using a unit vector. It is the second factor in each of these products.
37
Expression 38: "l" equals left bracket, 0 , 0 , 1 , right bracketl=0,0,1
38
each input vector is sx, sy, rz
39
normal of a tri = normalize(y-yhat of y onto v2), where y is (v1-v3 rotated around v2-v3)
40
Expression 41: "n" Subscript, "x" , Baseline left parenthesis, "n" Subscript, "x" 1 , Baseline , "n" Subscript, "x" 2 , Baseline , "n" Subscript, "x" 3 , Baseline , right parenthesis equalsnxnx1,nx2,nx3=