quat_from_axis_angle Function

public pure function quat_from_axis_angle(axis, angle) result(q)

The rotation by angle (radians) about axis (need not be unit length).

Arguments

Type IntentOptional Attributes Name
real(kind=wp), intent(in) :: axis(3)

rotation axis (any length; zero: the identity)
real(kind=wp), intent(in) :: angle

(radians)

Return Value real(kind=wp), (4)


Source Code

    pure function quat_from_axis_angle(axis, angle) result(q)
        real(wp), intent(in) :: axis(3)     !! rotation axis (any length; zero: the identity)
        real(wp), intent(in) :: angle       !! (radians)
        real(wp) :: q(4)
        real(wp) :: n
        n = norm2(axis)
        if (n == 0.0_wp) then
            q = quat_identity
        else
            q(1:3) = axis / n * sin(0.5_wp * angle)
            q(4) = cos(0.5_wp * angle)
        end if
    end function quat_from_axis_angle