/** * Returns the (4-space) angle in radians between this vector and * the vector parameter; the return value is constrained to the * range [0,PI]. * @param v1 the other vector * @return the angle in radians in the range [0,PI] */ public final float angle(Vector4f v1) { double vDot = this.dot(v1) / ( this.length()*v1.length() ); if( vDot < -1.0) vDot = -1.0; if( vDot > 1.0) vDot = 1.0; return((float) (Math.acos( vDot ))); }