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One must be careful when converting a rotation matrix to a quaternion, as several straightforward methods tend to be unstable when the trace (sum of the diagonal elements) of the rotation matrix is zero or very small. For a stable method of converting an orthogonal matrix to a quaternion, see the Rotation matrix#Quaternion.
If + + + is not a unit quaternion then the homogeneous form is still a scalar multiple of a rotation matrix, while the inhomogeneous form is in general no longer an orthogonal matrix. This is why in numerical work the homogeneous form is to be preferred if distortion is to be avoided.
Noting that any identity matrix is a rotation matrix, and that matrix multiplication is associative, we may summarize all these properties by saying that the n × n rotation matrices form a group, which for n > 2 is non-abelian, called a special orthogonal group, and denoted by SO(n), SO(n,R), SO n, or SO n (R), the group of n × n rotation ...
Equivalently, any rotation matrix R can be decomposed as a product of three elemental rotation matrices. For instance: R = X ( α ) Y ( β ) Z ( γ ) {\displaystyle R=X(\alpha )Y(\beta )Z(\gamma )} is a rotation matrix that may be used to represent a composition of extrinsic rotations about axes z , y , x , (in that order), or a composition of ...
A rotation of the vector through an angle θ in counterclockwise direction is given by the rotation matrix: = ( ), which can be viewed either as an active transformation or a passive transformation (where the above matrix will be inverted), as described below.
In quaternion notation, a proper (i.e., non-inverting) rotation in SO(4) is a proper simple rotation if and only if the real parts of the unit quaternions Q L and Q R are equal in magnitude and have the same sign.
A potential solution therefore is to represent the orientation in some other way. This could be as a rotation matrix, a quaternion (see quaternions and spatial rotation), or a similar orientation representation that treats the orientation as a value rather than three separate and related values. Given such a representation, the user stores the ...
This we recognize as the rotation matrix corresponding to quaternion w + i x + j y + k z {\displaystyle w+\mathbf {i} x+\mathbf {j} y+\mathbf {k} z\,\!} (by a formula Cayley had published the year before), except scaled so that w = 1 instead of the usual scaling so that w 2 + x 2 + y 2 + z 2 = 1.