/*
PLEASE NOTE THAT THE FOLLOWING DATA
MEMBER 'm'(which stands for mass IS REQUIRED ONLY FOR
HD SUBMISSIONS AND SHOULD BE SET
TO diameter * 0.05 FOR THE METHOD
collideWith(Ball) TO WORK CORRECTLY
*/
float m;
//You WILL need to implement a boolean checkCollisionWith(Ball other) method
//to correctly use collideWith method provided
DO NOT MODIFY THIS METHOD
void collideWith(Ball other) {
PVector bVect = new PVector();
bVect.x = other.x - x;
bVect.y = other.y - y;
float bVectMag = sqrt(bVect.x * bVect.x + bVect.y * bVect.y);
if (checkCollisionWith(other)) {
// get angle of bVect
float theta = atan2(bVect.y, bVect.x);
// precalculate trig values
float sine = sin(theta);
float cosine = cos(theta);
Ball[] bTemp = {
new Ball(), new Ball()
};
/* b[1]'s position is relative to b[0]'s
so you can use the vector between them (bVect) as the
reference point in the rotation expressions.
bTemp[0].x and bTemp[0].y will initialize
automatically to 0.0, which is what you want
since b[1] will rotate around b[0] */
bTemp[1].x = cosine * bVect.x + sine * bVect.y;
bTemp[1].y = cosine * bVect.y - sine * bVect.x;
// rotate Temporary velocities
PVector[] vTemp = {
new PVector(), new PVector()
};
PVector[] v = {
new PVector(speedX, speedY),
new PVector(other.speedX, other.speedY)
};
vTemp[0].x = cosine * v[0].x + sine * v[0].y;
vTemp[0].y = cosine * v[0].y - sine * v[0].x;
vTemp[1].x = cosine * v[1].x + sine * v[1].y;
vTemp[1].y = cosine * v[1].y - sine * v[1].x;
/* Now that velocities are rotated, you can use 1D
conservation of momentum equations to calculate
the final velocity along the x-axis. */
PVector[] vFinal = {
new PVector(), new PVector()
};
// final rotated velocity for b[0]
vFinal[0].x = ((m - other.m) * vTemp[0].x + 2 * other.m *
vTemp[1].x) / (m + other.m);
vFinal[0].y = vTemp[0].y;
// final rotated velocity for b[0]
vFinal[1].x = ((other.m - m) * vTemp[1].x + 2 * m *
vTemp[0].x) / (m + other.m);
vFinal[1].y = vTemp[1].y;
// hack to avoid clumping
bTemp[0].x += vFinal[0].x;
bTemp[1].x += vFinal[1].x;
/* Rotate ball positions and velocities back
Reverse signs in trig expressions to rotate
in the opposite direction */
// rotate balls
Ball[] bFinal = {
new Ball(), new Ball()
};
bFinal[0].x = cosine * bTemp[0].x - sine * bTemp[0].y;
bFinal[0].y = cosine * bTemp[0].y + sine * bTemp[0].x;
bFinal[1].x = cosine * bTemp[1].x - sine * bTemp[1].y;
bFinal[1].y = cosine * bTemp[1].y + sine * bTemp[1].x;
// update balls to screen position
other.x = constrain(x + bFinal[1].x, other.diameter/2, width-other.diameter/2);
other.y = constrain(y + bFinal[1].y, other.diameter/2, height-other.diameter/2);
x = constrain(x + bFinal[0].x, diameter/2, width-diameter/2);
y = constrain(y + bFinal[0].y, diameter/2, height-diameter/2);
// update velocities
speedX = cosine * vFinal[0].x - sine * vFinal[0].y;
speedY = cosine * vFinal[0].y + sine * vFinal[0].x;
other.speedX = cosine * vFinal[1].x - sine * vFinal[1].y;
other.speedY = cosine * vFinal[1].y + sine * vFinal[1].x;
}
}
}
