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updating CircleCollision to follow PVector syntax

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This commit is contained in:
Daniel Shiffman
2013-03-15 22:56:44 -04:00
parent 25677922a1
commit 4cde40675e
2 changed files with 132 additions and 125 deletions
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135
java/examples/Topics/Motion/CircleCollision/Ball.pde
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@@ -1,16 +1,131 @@
class Ball{
float x, y, r, m;
class Ball {
PVector position;
PVector velocity;
// default constructor
Ball() {
float r, m;
Ball(float x, float y, float r_) {
position = new PVector(x, y);
velocity = PVector.random2D();
velocity.mult(3);
r = r_;
m = r*.1;
}
Ball(float x, float y, float r) {
this.x = x;
this.y = y;
this.r = r;
m = r*.1;
void update() {
position.add(velocity);
}
void checkBoundaryCollision() {
if (position.x > width-r) {
position.x = width-r;
velocity.x *= -1;
}
else if (position.x < r) {
position.x = r;
velocity.x *= -1;
}
else if (position.y > height-r) {
position.y = height-r;
velocity.y *= -1;
}
else if (position.y < r) {
position.y = r;
velocity.y *= -1;
}
}
void checkCollision(Ball other) {
// get distances between the balls components
PVector bVect = PVector.sub(other.position, position);
// calculate magnitude of the vector separating the balls
float bVectMag = bVect.mag();
if (bVectMag < r + other.r) {
// get angle of bVect
float theta = bVect.heading();
// precalculate trig values
float sine = sin(theta);
float cosine = cos(theta);
/* bTemp will hold rotated ball positions. You
just need to worry about bTemp[1] position*/
PVector[] bTemp = {
new PVector(), new PVector()
};
/* this ball's position is relative to the other
so you can use the vector between them (bVect) as the
reference point in the rotation expressions.
bTemp[0].position.x and bTemp[0].position.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()
};
vTemp[0].x = cosine * velocity.x + sine * velocity.y;
vTemp[0].y = cosine * velocity.y - sine * velocity.x;
vTemp[1].x = cosine * other.velocity.x + sine * other.velocity.y;
vTemp[1].y = cosine * other.velocity.y - sine * other.velocity.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
PVector[] bFinal = {
new PVector(), new PVector()
};
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.position.x = position.x + bFinal[1].x;
other.position.y = position.y + bFinal[1].y;
position.add(bFinal[0]);
// update velocities
velocity.x = cosine * vFinal[0].x - sine * vFinal[0].y;
velocity.y = cosine * vFinal[0].y + sine * vFinal[0].x;
other.velocity.x = cosine * vFinal[1].x - sine * vFinal[1].y;
other.velocity.y = cosine * vFinal[1].y + sine * vFinal[1].x;
}
}
void display() {
noStroke();
fill(204);
ellipse(position.x, position.y, r*2, r*2);
}
}

122
java/examples/Topics/Motion/CircleCollision/CircleCollision.pde
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@@ -6,135 +6,27 @@
* Foundation Actionscript Animation: Making Things Move!
*/
Ball[] balls = {
new Ball(100, 400, 20),
new Ball(700, 400, 80)
};
PVector[] vels = {
new PVector(2.15, -1.35),
new PVector(-1.65, .42)
};
void setup() {
size(640, 360);
noStroke();
}
void draw() {
background(51);
fill(204);
for (int i = 0; i < 2; i++){
balls[i].x += vels[i].x;
balls[i].y += vels[i].y;
ellipse(balls[i].x, balls[i].y, balls[i].r*2, balls[i].r*2);
checkBoundaryCollision(balls[i], vels[i]);
for (Ball b : balls) {
b.update();
b.display();
b.checkBoundaryCollision();
}
checkObjectCollision(balls, vels);
balls[0].checkCollision(balls[1]);
}
void checkObjectCollision(Ball[] b, PVector[] v){
// get distances between the balls components
PVector bVect = new PVector();
bVect.x = b[1].x - b[0].x;
bVect.y = b[1].y - b[0].y;
// calculate magnitude of the vector separating the balls
float bVectMag = sqrt(bVect.x * bVect.x + bVect.y * bVect.y);
if (bVectMag < b[0].r + b[1].r){
// get angle of bVect
float theta = atan2(bVect.y, bVect.x);
// precalculate trig values
float sine = sin(theta);
float cosine = cos(theta);
/* bTemp will hold rotated ball positions. You
just need to worry about bTemp[1] position*/
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()
};
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 = ((b[0].m - b[1].m) * vTemp[0].x + 2 * b[1].m *
vTemp[1].x) / (b[0].m + b[1].m);
vFinal[0].y = vTemp[0].y;
// final rotated velocity for b[0]
vFinal[1].x = ((b[1].m - b[0].m) * vTemp[1].x + 2 * b[0].m *
vTemp[0].x) / (b[0].m + b[1].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
b[1].x = b[0].x + bFinal[1].x;
b[1].y = b[0].y + bFinal[1].y;
b[0].x = b[0].x + bFinal[0].x;
b[0].y = b[0].y + bFinal[0].y;
// update velocities
v[0].x = cosine * vFinal[0].x - sine * vFinal[0].y;
v[0].y = cosine * vFinal[0].y + sine * vFinal[0].x;
v[1].x = cosine * vFinal[1].x - sine * vFinal[1].y;
v[1].y = cosine * vFinal[1].y + sine * vFinal[1].x;
}
}
void checkBoundaryCollision(Ball ball, PVector vel) {
if (ball.x > width-ball.r) {
ball.x = width-ball.r;
vel.x *= -1;
}
else if (ball.x < ball.r) {
ball.x = ball.r;
vel.x *= -1;
}
else if (ball.y > height-ball.r) {
ball.y = height-ball.r;
vel.y *= -1;
}
else if (ball.y < ball.r) {
ball.y = ball.r;
vel.y *= -1;
}
}