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);
}
}
}
@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);
}
}
}