OrbitalMagnetComponent.java :  » Port » replicaisland-plus-text » com » replica » replicaisland » Android Open Source

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.replica.replicaisland;


public class OrbitalMagnetComponent extends GameComponent {
  private final static float DEFAULT_STRENGTH = 15.0f;

  private float mStrength;
  private Vector2 mCenter;
  private Vector2 mDelta;
  private Vector2 mRim;
  private Vector2 mVelocity;
  private float mMagnetRadius;
  private float mAreaRadius;
  
  public OrbitalMagnetComponent() {
        super();
        mCenter = new Vector2();
        mDelta = new Vector2();
        mRim = new Vector2();
        mVelocity = new Vector2();
        reset();
        setPhase(ComponentPhases.COLLISION_DETECTION.ordinal());
    }
    
    @Override
    public void reset() {
      mCenter.zero();
      mDelta.zero();
      mRim.zero();
      mVelocity.zero();
      mStrength = DEFAULT_STRENGTH;
      mAreaRadius = 0.0f;
      mMagnetRadius = 0.0f;
    }

    @Override
    public void update(float timeDelta, BaseObject parent) {
        GameObjectManager manager = sSystemRegistry.gameObjectManager;
        if (manager != null) {
          GameObject player = manager.getPlayer();
          if (player != null) {
            GameObject parentObject =  (GameObject)parent;
            applyMagnetism(player, 
                parentObject.getCenteredPositionX(), 
                parentObject.getCenteredPositionY(),
                timeDelta);
          }
        }
    }
    
    private void applyMagnetism(GameObject target, float centerX, float centerY, float timeDelta) {
      mCenter.set(centerX, centerY);
      final float targetX = target.getCenteredPositionX();
      final float targetY = target.getCenteredPositionY();
      mDelta.set(targetX, targetY);
      mDelta.subtract(mCenter);
      
      final float distanceFromCenter2 = mDelta.length2();
      final float area2 = mAreaRadius * mAreaRadius;
      if (distanceFromCenter2 < area2) {
        mRim.set(mDelta);
        mRim.normalize();
        mRim.multiply(mMagnetRadius);
        mRim.add(mCenter);
        // rim is now the closest point on the magnet circle
        
        // remove gravity
        final Vector2 targetVelocity = target.getVelocity();
        GravityComponent gravity = target.findByClass(GravityComponent.class);
            final Vector2 gravityVector = gravity.getGravity();
            mVelocity.set(gravityVector);
            mVelocity.multiply(timeDelta);
            targetVelocity.subtract(mVelocity);
            
        mDelta.add(targetVelocity);
        mDelta.normalize();
        mDelta.multiply(mMagnetRadius);
        mDelta.add(mCenter);
        
        // mDelta is now the next point on the magnet circle in the direction of
        // movement.
        
        mDelta.subtract(mRim);
        mDelta.normalize();
        // Now mDelta is the tangent to the magnet circle, pointing in the direction
        // of movement.
        
        mVelocity.set(mDelta);
        mVelocity.normalize();
        
        // mVelocity is now the direction to push the player
        
      mVelocity.multiply(mStrength);
      float weight = 1.0f;
      if (distanceFromCenter2 > mMagnetRadius * mMagnetRadius) {
        float distance = (float)Math.sqrt(distanceFromCenter2);
        weight = (distance - mMagnetRadius) / (mAreaRadius - mMagnetRadius);
        weight = 1.0f - weight;
        mVelocity.multiply(weight);
      }
      final float speed = targetVelocity.length();
      targetVelocity.add(mVelocity);
      if (targetVelocity.length2() > (speed * speed)) {
        targetVelocity.normalize();
        targetVelocity.multiply(speed);
      }
        
      }
      
    }
    
    public void setup(float areaRadius, float orbitRadius) {
      mAreaRadius = areaRadius;
      mMagnetRadius = orbitRadius;
    }
}