repelrule.java

j2me小游戏 j2me小游戏 j2me小游戏 j2me小游戏

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package example.boids;


class RepelRule
    implements BoidRule, BoidsConstants
{
    private int totalVx;
    private int totalVy;
    private Boid currentBoid;
    private static final int REPEL_FACTOR = (1 << FIXED_POINT_SHIFT);
    private static final int REPEL_RANGE = 10;
    private static final int REPEL_RANGE_SQUARED = REPEL_RANGE * REPEL_RANGE;


    RepelRule()
    {
    }


    public void reset(Boid boid)
    {
        totalVx = 0;
        totalVy = 0;
        currentBoid = boid;
    }


    public void applyTo(Boid boid)
    {
        int diffX = currentBoid.getX() - boid.getX();
        int diffY = currentBoid.getY() - boid.getY();
        // range squared can be too large for our fixed point, so do this
        // in normal integers
        int dx = diffX >> FIXED_POINT_SHIFT;
        int dy = diffY >> FIXED_POINT_SHIFT;
        int rangeSquared = dx * dx + dy * dy;
        if (rangeSquared < REPEL_RANGE_SQUARED)
        {
            int factor = (REPEL_FACTOR * (REPEL_RANGE_SQUARED - rangeSquared))
                                                 / REPEL_RANGE_SQUARED;
            totalVx += (factor * diffX) >> FIXED_POINT_SHIFT;
            totalVy += (factor * diffY) >> FIXED_POINT_SHIFT;
        }
    }


    public int getVx()
    {
        return totalVx;
    }


    public int getVy()
    {
        return totalVy;
    }
}