public void Bounce(Ball2D ball)
{
foreach (Line2D line in lines)
{
line.Bounce(ball);
}
}
public Line2D(double x1, double x2, double y1, double y2)
{
p1 = new Point2D(x1, y1);
p2 = new Point2D(x2, y2);
endPoints[0] = new Ball2D(p1, new Point2D(0, 0), 0.005);
endPoints[0].Mass = double.MaxValue;
endPoints[1] = new Ball2D(p2, new Point2D(0, 0), 0.005);
endPoints[1].Mass = double.MaxValue;
}
public Line2D(Point2D p1, Point2D p2)
{
this.p1 = p1;
this.p2 = p2;
endPoints[0] = new Ball2D(p1, new Point2D(0, 0), 0.005);
endPoints[0].Mass = double.MaxValue;
endPoints[1] = new Ball2D(p2, new Point2D(0, 0), 0.005);
endPoints[1].Mass = double.MaxValue;
}
/// <summary>
/// Perform the collision between two ball objects, this and other ball
/// </summary>
/// <param name="otherBall"></param>
public void PerformCollision(Ball2D otherBall)
{
//nothing to do if not colliding
if (!IsColliding(otherBall))
{
return;
}
Point2D difference = this - otherBall;
double distance = difference.Magnitude;
//minimum translation distance
//fudge by a small factor of 1.1 to force them to move apart by at least a slight gap
Point2D mtd = difference * (this.Radius + otherBall.Radius - distance) / distance * 1.1;
//get the reciprocal of the masses
double thisMassReciprocal = 1 / mass;
double otherMassReciprocal = 1 / otherBall.Mass;
//push the balls apart by the minimum translation difference
Point2D center = mtd * (thisMassReciprocal / (thisMassReciprocal + otherMassReciprocal));
this.X += center.X;
this.Y += center.Y;
Point2D otherBallCenter = mtd * (otherMassReciprocal / (thisMassReciprocal + otherMassReciprocal));
otherBall.X -= otherBallCenter.X;
otherBall.Y -= otherBallCenter.Y;
//now we "normalize" the mtd to get a unit vector of length 1 in the direction of the mtd
mtd.Normalize();
//impact the velocity due to the collision
Point2D v = this.velocity - otherBall.velocity;
double vDotMtd = v * mtd;
if (double.IsNaN(vDotMtd))
{
return;
}
if (vDotMtd > 0)
{
return; //the balls are already moving in opposite directions
}
//work out collision effect
double i = -(1 + elasticity) * vDotMtd / (thisMassReciprocal + otherMassReciprocal);
Point2D impulse = mtd * i;
//change the balls velocities
this.velocity += impulse * thisMassReciprocal;
otherBall.velocity -= impulse * otherMassReciprocal;
}
/// <summary>
/// determine the line that is normal from this line to a ball center
/// </summary>
/// <param name="ball"></param>
/// <returns></returns>
public Point2D NormalToBall(Ball2D ball)
{
Point2D v = p1 - p2;
Point2D ballToLine = ball - p1;
Point2D normal = v.Normal;
//make normal a unit vector
normal.Normalize();
if (normal * ballToLine < 0)
{
normal *= -1;
}
return(normal);
}
public bool Bounce(Ball2D ball)
{
//determine the normla vector from the line to the ball
Point2D normal = NormalToBall(ball);
//make a temporary line of this line moved one radius towards ball (bounce off center)
Line2D aLineTemp = new Line2D(P1 + normal * ball.Radius, p2 + normal * ball.Radius);
//we need to kmow where the ball will be in one step
Point2D ballNextStep = ball + ball.Velocity;
//make a line from where the ball is now to the location at the next step
Line2D ballPath = new Line2D(ball, ballNextStep);
//find point of intersection between line and path of the ball
Point2D intersectionPoint = aLineTemp.LineIntersectionPoint(ballPath);
//perfrom the bounce if necessary
//bounce off endpoints if necessary
if (endPoints[0].IsColliding(ball))
{
endPoints[0].PerformCollision(ball);
return(true);
}
else if (endPoints[1].IsColliding(ball))
{
endPoints[1].PerformCollision(ball);
return(true);
}
//if the intersection point is within line segment
//and the ball is moving towards the line
else if (ball.Velocity.Magnitude < (intersectionPoint - ball).Magnitude && normal * ball.Velocity < 0)
{
return(false);
}
else if (aLineTemp.Contains(intersectionPoint) && normal * ball.Velocity < 0)
{
Line2D reflectionLine = new Line2D(ball + ball.Velocity, intersectionPoint);
Point2D velocityDirection = -1 * reflectionLine.Reflection(NormalToBall(ball));
velocityDirection.Normalize();
ball.Velocity = velocityDirection * ball.Velocity.Magnitude * ball.Elasticity;
Point2D ballLocation = intersectionPoint - reflectionLine.Reflection(NormalToBall(ball)) * ball.Elasticity;
ball.X = ballLocation.X;
ball.Y = ballLocation.Y;
return(true);
}
return(false);
}
/// <summary>
/// Check to see if this ball is colliding with another ball
/// </summary>
/// <param name="otherBall"></param>
/// <returns></returns>
public bool IsColliding(Ball2D otherBall)
{
Point2D distance = this - otherBall;
return(distance.Magnitude < this.Radius + otherBall.Radius);
}
public Line2D()
{
p1 = new Point2D(); p2 = new Point2D();
endPoints[0] = new Ball2D();
endPoints[1] = new Ball2D();
}
