Given a point O(oriX,oriY) and a vector V(oriDX,oriDY), with V origin in O and V unit vector, tells how much we need to rotate V around O so that V points to Target. - Java java.lang

Java examples for java.lang:Math Vector

  1. HOME
  2. Java
  3. java.lang
  4. Math Vector

Description

Given a point O(oriX,oriY) and a vector V(oriDX,oriDY), with V origin in O and V unit vector, tells how much we need to rotate V around O so that V points to Target.

Demo Code


//package com.java2s;

public class Main {
    public static final float PI = (float) Math.PI;

    /**//  w ww  .j  a  va  2  s  . c o  m
     * Given a point O(oriX,oriY) and a vector V(oriDX,oriDY), 
     * with V origin in O and V unit vector, tells how much we
     * need to rotate V around O so that V points to Target.
     * @param oriX O x coordinate
     * @param oriY O y coordinate
     * @param oriDX V x coordinates
     * @param oriDY V y coordinates
     * @param targetX Target x coordinate
     * @param targetY Target y coordinate
     * @return Angle to rotate around O so V points to Target
     */
    static public float getAngleBetween(float oriX, float oriY,
            float oriDX, float oriDY, float targetX, float targetY) {
        float cos = oriDX;
        float sin = oriDY;

        float currentAngle = (float) Math.acos(cos);
        if (sin < 0)
            currentAngle = -currentAngle;

        return getAngleBetween(oriX, oriY, currentAngle, targetX, targetY);
    }

    /**
     * Given a point O(oriX,oriY) and a rotation angle around O 
     * oriAngle, tells how much rotation we still need to add to
     * oriAngle so we are "looking at the target" from O.
     * @param oriX O x coordinate
     * @param oriY O y coordinate
     * @param oriAngle initial angle of rotation around O, within [-2PI,PI]
     * @param targetX Target x coordinate
     * @param targetY Target y coordinate
     * @return Angle to rotate around O so V points to Target
     */
    static public float getAngleBetween(float oriX, float oriY,
            float oriAngle, float targetX, float targetY) {
        float currentAngle = oriAngle;

        //Normalized vector to target
        float vectorToTargetX = targetX - oriX;
        float vectorToTargetY = targetY - oriY;

        float normSquare = vectorToTargetX * vectorToTargetX
                + vectorToTargetY * vectorToTargetY;
        if (normSquare == 0f) {
            //Target and origin are the same.
            return 0f;
        }
        float norm = (float) Math.sqrt(normSquare);

        vectorToTargetX /= norm;
        vectorToTargetY /= norm;

        //calculate target angle
        float cos = vectorToTargetX;
        float sin = vectorToTargetY;

        float targetAngle = (float) Math.acos(cos);
        if (sin < 0)
            targetAngle = -targetAngle;

        //How much should we rotate?
        float angleBetweenTargetAndDirection = targetAngle - currentAngle;
        if (angleBetweenTargetAndDirection < 0
                && angleBetweenTargetAndDirection < -Math.PI) {
            angleBetweenTargetAndDirection += 2 * Math.PI;
        } else if (angleBetweenTargetAndDirection > 0
                && angleBetweenTargetAndDirection > Math.PI) {
            angleBetweenTargetAndDirection -= 2 * Math.PI;
        }

        return angleBetweenTargetAndDirection;
    }
}

Related Tutorials