兩個球之間的碰撞

Question

我想模擬兩個球之間的碰撞，一個由加速度計控制，另一個隨機移動。 如何實現這些碰撞？我設法設定了球和碰撞的條件，但除此之外，我不知道如何表示碰撞向量。算法或提示將不勝感激:)我有兩個球存儲在變量中的x和y速度和位置。我還設法使用了一些基本的（但錯誤的）碰撞機制，隨機運動球反轉了它的x和y速度。但我也有問題，如果球移動得太快，它們會重疊。我該怎麼辦？

package perseus.gfx.test; 

import everything; 

public class Ball extends View { 
RectF lol; 
Paint paint, lpaint; 
Bitmap bitmap; 
Canvas canvas; 
private float ballx = 150; 
private float bally = 140; 
private double speedx = 0; 
private double speedy = 0; //ignore 
private double accx, accy=0; 
private float rad = 15; 
private float mult = 0.5f; 
private float friction = -0.001f; 
private double xv, yv, xS, yS; 
private long ltm = -1; 
int width, height; 
int xmax, ymax; 
int xmin, ymin; 

public Ball(Context context) { 
    super(context); 
    lol = new RectF(); 
    paint = new Paint(); 
    paint.setColor(Color.CYAN); 
    lpaint = new Paint(); 
    lpaint.setColor(Color.GRAY);     


} 
public double getSpeedX() 
{ 
    return this.speedx; 
} 
public double getSpeedY() 
{ 
    return this.speedy; 
} 
public void setSpeedX(double x) 
{ 
    this.speedx = x; 
} 
public void setSpeedY(double y) 
{ 
    this.speedy = y; 
} 
public void setColor(int c) 
{ 
    paint.setColor(c); 
} 
public float getRad() 
{ 
    return this.rad; 
} 
public void setRad(float rad) 
{ 
    this.rad = rad; 
} 
public void setAX(double accx) 
{ 
    this.accx = accx; 
} 
public void setAY(double accy) 
{ 
    this.accy = accy; 
} 
public float getX() 
{ 
    return this.ballx; 
} 
public void setX(float ballx) 
{ 
    this.ballx = ballx; 
} 
public float getY() 
{ 
    return this.bally; 
} 
public void setY(float bally) 
{ 
    this.bally = bally; 
} 
public void moveBall() { 


    xv = accx * mult; 
    yv = accy * mult; 

    ballx -= xv * mult; 
    bally -= yv * mult; 

    ballx +=speedx; 
    bally +=speedy; 


    /*ballx +=speedx; 
    bally +=speedy;*/ 

    // Collision detection 
    if (ballx + rad > xmax) { 
     speedx = -speedx;  
     ballx = xmax-rad; 
    }   
    else if (ballx - rad < 0) { 
     speedx = -speedx; 
     ballx = rad; 
    } 
    if (bally + rad > 2*ymax/3) { 
     speedy = -speedy; 
     bally = 2*ymax/3 - rad; 


    } 

    else if (bally - rad < 0) { 
     speedy = -speedy; 
     bally = rad; 
    }       

    try { 
     Thread.sleep(20); 
    } catch(InterruptedException e) {} 

    invalidate(); 

} 
@Override 
public void onMeasure(int widthM, int heightM) 
{ 
    width = View.MeasureSpec.getSize(widthM); 
    height = View.MeasureSpec.getSize(heightM); 
    xmax = width-1; 
    ymax = height-1; 
    xmin = 0; 
    ymin = 0; 
    setMeasuredDimension(width, height); 
    bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888); 
    canvas = new Canvas(bitmap); 


} 
@Override 
public void onDraw(Canvas canvas) 
{ 
    canvas.drawBitmap(bitmap, 0, 0, paint); 
    lol.set(ballx - rad, bally-rad, ballx + rad, bally+rad); 
    canvas.drawLine(0, 2*height/3, width, 2*height/3, lpaint); 
    /*canvas.drawOval(lol, paint);*/ 
    canvas.drawCircle(ballx, bally, rad, paint); 
    canvas.drawText(xv + " " + yv, 0, height/2, lpaint); 
    canvas.save(); 
    moveBall(); 
    canvas.restore(); 

} 



} 

這是我的球課，我的主要活動是：

package perseus.gfx.test; 
import everything; 
public class GfxActivity extends Activity implements OnSeekBarChangeListener, OnItemSelectedListener, SensorEventListener { 

ViewGroup.LayoutParams vg = new ViewGroup.LayoutParams(-1, -1); 
double velx, vely; 
double x, y; 
float radi; 
double finx, finy; 
float finrad; 

long lastSensorUpdate = -1; 
SensorManager sm; 
static double ux, uy; //initial ball velocity 
SeekBar velo, rad; 
Spinner colour; 
Ball ball, tester; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    ball = new Ball(this); 
    tester = new Ball(this); 
    setContentView(R.layout.main); 
    addContentView(ball, vg); 

    addContentView(tester, vg); 
    sm = (SensorManager)getSystemService(SENSOR_SERVICE); 
    sm.registerListener(this, sm.getDefaultSensor(Sensor.TYPE_ORIENTATION), SensorManager.SENSOR_DELAY_GAME); 
    colour = (Spinner)findViewById(R.id.color); 
    colour.setOnItemSelectedListener(this); 
    ArrayAdapter<CharSequence> aa = ArrayAdapter.createFromResource(this, R.array.colors, android.R.layout.simple_spinner_item); 
    aa.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); 
    colour.setAdapter(aa); 
    velo = (SeekBar)findViewById(R.id.vel); 
    velo.setOnSeekBarChangeListener(this); 
    rad = (SeekBar)findViewById(R.id.rad); 
    rad.setOnSeekBarChangeListener(this); 
    ux = ball.getSpeedX(); 
    uy = ball.getSpeedY(); 
    radi = ball.getRad(); 
    tester.setSpeedX(5); 
    tester.setSpeedY(3); 
    tester.setX(0); 
    tester.setY(0); 
    tester.setColor(Color.DKGRAY); 
} 
@Override 
public void onProgressChanged(SeekBar seeker, int arg1, boolean arg2) {  
    switch(seeker.getId()) 
    { 
    case R.id.vel: 
     x = ball.getSpeedX(); 
     y = ball.getSpeedY(); 

     if(x<0) 
      finx = -ux-arg1;    
     else if(x >= 0) 
      finx = ux+arg1; 

     if(y<0) 
      finy = -uy-arg1;   
     else if(finy>=0) 
      finy = uy+arg1; 

     ball.setSpeedX(finx); 
     ball.setSpeedY(finy); 
     break; 

    case R.id.rad:   
     finrad = radi + arg1; 
     ball.setRad(finrad); 
     break; 
    } 
} 
@Override 
public void onStartTrackingTouch(SeekBar arg0) { 
    //nothing lol 
} 
@Override 
public void onStopTrackingTouch(SeekBar arg0) { 
    //nothing lol 
} 

@Override 
public void onItemSelected(AdapterView<?> parent, View v, int position, 
     long id) { 
    switch(position) 
    { 
    case 0: 
     ball.setColor(Color.CYAN); 
     break; 
    case 1: 
     ball.setColor(Color.RED); 
     break; 
    case 2: 
     ball.setColor(Color.BLUE); 
     break; 
    case 3: 
     ball.setColor(Color.GREEN); 
     break; 
    } 

} 
@Override 
public void onNothingSelected(AdapterView<?> arg0) { 

} 
@Override 
public void onAccuracyChanged(Sensor arg0, int arg1) { 
    // TODO Auto-generated method stub 

} 
@Override 
public void onSensorChanged(SensorEvent sensorevent) { 
    if(sensorevent.sensor.getType() == Sensor.TYPE_ORIENTATION) 
    { 
      ball.setAX(sensorevent.values[2]); 
      ball.setAY(sensorevent.values[1]);       
    } 

     if((Math.pow(ball.getX() - tester.getX(), 2) + Math.pow(ball.getY() - tester.getY(), 2)) <= (ball.getRad() + tester.getRad())*(ball.getRad() + tester.getRad())) 
     { 

       /*tester.setSpeedX(-1*tester.getSpeedX()); 
       tester.setSpeedY(-1*tester.getSpeedY());*/ 
     } 
    } 

} 

球和檢測儀是我的兩個球，球被加速計控制。我知道代碼不是非常高效，但我認爲我會先着手實現碰撞。

Answer 1

在改進碰撞算法之前，您需要考慮幾件事情 - 碰撞是彈性碰撞嗎？你能把這兩個球當作點源嗎？無論哪種方式，你的動量向量將被保留，所以你可以使用牛頓的P initial = P final來確定新的向量。

這兩個球可能重疊，因爲您運行碰撞檢測算法的速率比改變球的位置的速度慢。

如果您發佈代碼示例，我們可以幫助您更好。

Answer 2

考慮到你有xVel1，yVel1，xVel2，yVel2; xPos1，yPos1，xPos2，yPos2; mass1，mass2;檢測到碰撞後：

double theta = Math.atan2(yPos1-yPos2, xPos1-xPos2); 
double c = Math.cos(theta); 
double s = Math.sin(theta); 
double xVel1prime = xVel1*c+yVel1*s; 
double xVel2prime = xVel2*c+yVel2*s; 
double yVel1prime = yVel1*c-xVel1*s; 
double yVel2prime = yVel2*c-xVel2*s; 
double P = (mass1*xVel1prime+mass2*xVel2prime); 
double V = (xVel1prime-xVel2prime); 
double v2f = (P+mass1*V)/(mass1+mass2); 
double v1f = v2f-xVel1prime+xVel2prime; 
xVel1prime = v1f; 
xVel2prime = v2f; 

xVel1 = xVel1prime*c-yVel1prime*s; 
xVel2 = xVel2prime*c-yVel2prime*s; 
yVel1 = yVel1prime*c+xVel1prime*s; 
yVel2 = yVel2prime*c+xVel2prime*s; 
//velocities updated