Quote - kuroyume: I would love the info on converting right-handed matrix to left-handed, I have some idea of it but mostly I'm making educated guesses based on what I see in various CR2s I have looked at.

Remember that this is changing a right-handed coordinate system into a left-handed coordinate system (in my case, I do this from Poser (right) to Cinema 4D (left)).

The matrix math is pretty straight forward (post-multiplication):

Matrix lhm = reflect * transpose * rhm

In words, the right-handed matrix is transposed and then multipled by a reflection matrix (about the z-axis).

Transposing the matrix involves a sort-of diagonal flip of the 4x4 matrix:

Right-handed (row-vector representation):

v1.x, v1.y, v1.y, 0
v2.x, v2.y, v2.z, 0
v3.x, v3.y, v3.z, 0
t.x, t.y, t.z, 1

becomes Left-handed (column-vector representation):

v1.x, v2.x, v3.x, t.x
v1.y, v2.y, v3.y, ty
v1.z, v2.z, v3.z, tz
0, 0, 0, 1

The left-handed reflection matrix is then:

1, 0, 0, 0
0, 1, 0, 0
0, 0, -1, 0
0, 0, 0, 1

The -1 reflects rotations and translations from the one system to the other (about the z-axis - x-y plane).

C makes it easy to shoot yourself in the foot. C++ makes it harder, but when you do, you blow your whole leg off.

 -- Bjarne Stroustrup

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