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How is the rotation of r around the rotation axis decomposed?


Asked by Olive Brown on Dec 11, 2021 FAQ



A rotation R around axis u can be decomposed using 3 endomorphisms P, (I − P), and Q (click to enlarge). Given a 3 × 3 rotation matrix R, a vector u parallel to the rotation axis must satisfy. R u = u , {\displaystyle R\mathbf {u} =\mathbf {u} ,}. since the rotation of u around the rotation axis must result in u.
Likewise,
According to Euler's rotation theorem, simultaneous rotation along a number of stationary axes at the same time is impossible. If two rotations are forced at the same time, a new axis of rotation will appear. This article assumes that the rotation is also stable, such that no torque is required to keep it going.
Also, This is not commutative because QD != QN. The sum of two perpendicular to D vectors give the vector that is perprndicular to D too, because thay lay in one plane , and tham composition lay in that plane. It all work in the Pure rotation , when D represent the direction in LOCAL object orientation frame.
Indeed,
Take the axis you want to find the rotation around, and find an orthogonal vector to it. Rotate this new vector using your quaternion. Project this rotated vector onto the plane the normal of which is your axis
In fact,
So, if we combine several rotations about the coordinate axis, the matrix of the resulting transformation is itself an orthogonal matrix. One way of implementing a rotation about an arbitrary axis through the origin is to combine rotations about the z, y, and x axes.