On Wed, Apr 5, 2017 at 5:35 PM, Igor Mironchik <igor.mironc...@gmail.com>
wrote:

> But why it can be needed in 3D?
>

If the matrix is unitary (i.e. a rotation matrix), that's the inverse
transform, but a general affine transformation is not unitary.
In the common case it's just the application of the transposed M to a
vector. Matrix multiplications aren't commutative, but it holds that:
(M*v)^T = (v^T)*(M^T) (^T is used as notation for transposition)
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