compute a 4x4 Transformation matrix for rotation around an arbitrary axis
getTrafoRotaxis(pt1, pt2, theta)
pt1
: numeric vector of length 3, defining first point on the rotation axis.pt2
: numeric vector of length 3, defining second point on the rotation axis.theta
: angle to rotate in radians. With pt1 being the viewpoint, the rotation is counterclockwise.the resulting matrix can be used in applyTransform