boid.java

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// Copyright 2002 Nokia Corporation. 
// 
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// 
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// and may be changed substantially prior to final release. Nokia Corporation 
// retains the right to make changes to this source code at 
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// purposes only. 
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package example.boids;

import javax.microedition.lcdui.*;


class Boid
    implements BoidsConstants
{
    private int x;
    private int y;
    private int vx;
    private int vy;
    private int speed;
    private final int red;
    private final int green;
    private final int blue;
    private final BoidsCanvas canvas;

    private static final BoidRule gatherRule = new GatherRule();
    private static final BoidRule repelRule = new RepelRule();
    private static final BoidRule alignRule = new AlignRule();

    private static final int MAX_SPEED = 5 << FIXED_POINT_SHIFT;
    private static final int MAX_FLAP = 10;
    private static final int LENGTH = 10 << FIXED_POINT_SHIFT;
    private static final int EDGE_REPEL_DISTANCE = 20 << FIXED_POINT_SHIFT;
    private static final int EDGE_REPEL_FACTOR = (1 << FIXED_POINT_SHIFT) / 4;


    Boid(int x, int y,
         int vx, int vy,
         int red, int green, int blue,
         BoidsCanvas canvas)
    {
        this.x = x;
        this.y = y;
        this.vx = vx;
        this.vy = vy;
        this.red = red;
        this.green = green;
        this.blue = blue;
        this.canvas = canvas;
    }


    int getX()
    {
        return x;
    }


    int getY()
    {
        return y;
    }


    int getVx()
    {
        return vx;
    }


    int getVy()
    {
        return vy;
    }


    void tick()
    {
        gatherRule.reset(this);
        canvas.applyRule(gatherRule, this);
        repelRule.reset(this);
        canvas.applyRule(repelRule, this);
        alignRule.reset(this);
        canvas.applyRule(alignRule, this);

        vx += gatherRule.getVx() + repelRule.getVx() + alignRule.getVx();
        vy += gatherRule.getVy() + repelRule.getVy() + alignRule.getVy();

        repelFromEdges();
        
        speed = BoidsUtils.squareRoot(vx * vx + vy * vy);
        if (speed > MAX_SPEED)
        {
            int factor = (MAX_SPEED << FIXED_POINT_SHIFT) / speed;
            vx = (vx * factor) >> FIXED_POINT_SHIFT;
            vy = (vy * factor) >> FIXED_POINT_SHIFT;
            speed = MAX_SPEED;
        }

        x += vx;
        y += vy;
    }


    private void repelFromEdges()
    {
        if (x < EDGE_REPEL_DISTANCE)
        {
            vx += ((EDGE_REPEL_DISTANCE - x) * EDGE_REPEL_FACTOR)
                                                    >> FIXED_POINT_SHIFT;
        }
        else
        {
            int width = canvas.getWidth() << FIXED_POINT_SHIFT;
            if (x > width - EDGE_REPEL_DISTANCE)
            {
                vx -= ((x - (width - EDGE_REPEL_DISTANCE)) * EDGE_REPEL_FACTOR)
                                                    >> FIXED_POINT_SHIFT;
            }
        }

        if (y < EDGE_REPEL_DISTANCE)
        {
            vy += ((EDGE_REPEL_DISTANCE - y) * EDGE_REPEL_FACTOR)
                                                    >> FIXED_POINT_SHIFT;
        }
        else
        {
            int height = canvas.getHeight() << FIXED_POINT_SHIFT;
            if (y > height - EDGE_REPEL_DISTANCE)
            {
                vy -= ((y - (height - EDGE_REPEL_DISTANCE)) * EDGE_REPEL_FACTOR)
                                                    >> FIXED_POINT_SHIFT;
            }
        }
    }


    void draw(Graphics g)
    {
        // calculate lengths; for simplicity, don't draw
        // stationary boids (how would we show their direction?)
        if (speed != 0)
        {
            int lx = vx * LENGTH / speed;
            int ly = vy * LENGTH / speed;
            int xHead = (x + (lx>>1)) >> FIXED_POINT_SHIFT;
            int yHead = (y + (ly>>1)) >> FIXED_POINT_SHIFT;
            int xEye = x >> FIXED_POINT_SHIFT;
            int yEye = y >> FIXED_POINT_SHIFT;
            int xTail = (x - (lx>>2)) >> FIXED_POINT_SHIFT;
            int yTail = (y - (ly>>2)) >> FIXED_POINT_SHIFT;
            int xLeft = (x - ((lx+ly)>>1)) >> FIXED_POINT_SHIFT;
            int yLeft = (y - ((ly-lx)>>1)) >> FIXED_POINT_SHIFT;
            int xRight = (x - ((lx-ly)>>1)) >> FIXED_POINT_SHIFT;
            int yRight = (y - ((ly+lx)>>1)) >> FIXED_POINT_SHIFT;
            g.setColor(red, green, blue);
            g.drawLine(xLeft, yLeft, xTail, yTail);
            g.drawLine(xRight, yRight, xTail, yTail);
            g.drawLine(xLeft, yLeft, xHead, yHead);
            g.drawLine(xRight, yRight, xHead, yHead);
            g.setColor(0, 0, 0);
            g.drawLine(xEye, yEye, xEye, yEye);
        }
    }
}