public Vector2 Intersection(Line2D line)
{
float tThis, tThat;
IntersectTees(line, out tThis, out tThat);
return Point1 + tThis * (Point2 - Point1);
}
public Vector2 SegmentIntersection(Line2D line)
{
float tThis, tThat;
IntersectTees(line, out tThis, out tThat);
if (tThis < 0 || tThis > 1 || tThat < 0 || tThat > 1)
return new Vector2(float.NaN, float.NaN);
return Point1 + tThis * (Point2 - Point1);
}
protected override void Update(GameTime gameTime)
{
// Allows the game to exit
if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
this.Exit();
// Calculate new velocity and position
Vector2 acceleration2D = Vector2.Zero;
lock (accelerationLock)
{
acceleration2D = new Vector2(acceleration.X, -acceleration.Y);
}
float elapsedSeconds = (float)gameTime.ElapsedGameTime.TotalSeconds;
ballVelocity += GRAVITY * acceleration2D * elapsedSeconds;
Vector2 oldPosition = ballPosition;
ballPosition += ballVelocity * elapsedSeconds;
bool needAnotherLoop = false;
do
{
needAnotherLoop = false;
foreach (Line2D line in borders)
{
Line2D shiftedLine = line.ShiftOut(BALL_RADIUS * line.Normal);
Line2D ballTrajectory = new Line2D(oldPosition, ballPosition);
Vector2 intersection = shiftedLine.SegmentIntersection(ballTrajectory);
float angleDiff = MathHelper.WrapAngle(line.Angle - ballTrajectory.Angle);
if (Line2D.IsValid(intersection) && angleDiff > 0 &&
Line2D.IsValid(Vector2.Normalize(ballVelocity)))
{
float beyond = (ballPosition - intersection).Length();
ballVelocity = BOUNCE * Vector2.Reflect(ballVelocity, line.Normal);
ballPosition = intersection + beyond * Vector2.Normalize(ballVelocity);
needAnotherLoop = true;
break;
}
}
}
while (needAnotherLoop);
base.Update(gameTime);
}
void IntersectTees(Line2D line, out float tThis, out float tThat)
{
float den = line.Vector.Y * this.Vector.X - line.Vector.X * this.Vector.Y;
tThis = (line.Vector.X * (this.Point1.Y - line.Point1.Y) -
line.Vector.Y * (this.Point1.X - line.Point1.X)) / den;
tThat = (this.Vector.X * (this.Point1.Y - line.Point1.Y) -
this.Vector.Y * (this.Point1.X - line.Point1.X)) / den;
}
