// The Constructor (called when the object is first created)
Particle(Vector3D a, Vector3D v, Vector3D l, float r_) {
acc = a.copy();
vel = v.copy();
loc = l.copy();
r = r_;
timer = 100.0f;
}
// Function to update location
public void update() {
// As long as we aren't dragging the pendulum, let it swing!
if (!dragging) {
float G = 0.4f; // Arbitrary universal gravitational constant
theta_acc = (-1 * G / r) * sin(theta); // Calculate acceleration (see:
// http://www.myphysicslab.com/pendulum1.html)
theta_vel += theta_acc; // Increment velocity
theta_vel *= damping; // Arbitrary damping
theta += theta_vel; // Increment theta
}
loc.setXY(r * sin(theta), r * cos(theta)); // Polar to cartesian conversion
loc.add(origin); // Make sure the location is relative to the pendulum's origin
}
void wander() {
float wanderR = 10.0f; // radius for our "wander circle"
float wanderD = 20.0f; // distance for our "wander circle"
wandertheta += random(-1, 1); // randomly changet wander theta
// now we have to calculate the new location to steer towards on the wander circle
Vector3D v = vel.copy();
v.normalize(); // our heading
float xoff =
wanderD * v.x() + wanderR * cos(wandertheta); // x spot on circle based on heading
float yoff =
wanderD * v.y() + wanderR * sin(wandertheta); // y spot on circle based on heading
Vector3D target = Vector3D.add(loc, new Vector3D(xoff, yoff)); // add the location
acc.add(steer(target, false)); // steer towards it
}
// look, we can have more than one constructor!
Particle(Vector3D l) {
acc = new Vector3D(0, 0.05f, 0);
// ooooh, bad random, random bad
vel = new Vector3D(random(-1, 1), random(-2, 0), 0);
loc = l.copy();
r = 10.0f;
timer = 100.0f;
}
public void drag() {
// If we are draging the ball, we calculate the angle between the
// pendulum origin and mouse location
// we assign that angle to the pendulum
if (dragging) {
Vector3D diff =
Vector3D.sub(origin, new Vector3D(mouseX, mouseY)); // Difference between 2 points
theta = atan2(-1 * diff.y, diff.x) - radians(90); // Angle relative to vertical axis
}
}
// a method that calculates a steering vector towards a target
// takes a second argument, if true, it slows down as it approaches the target
Vector3D steer(Vector3D target, boolean slowdown) {
Vector3D steer; // the steering vector
Vector3D desired =
Vector3D.sub(target, loc); // a vector pointing from the location to the target
float d = desired.magnitude(); // distance from the target is the magnitude of the vector
// if the distance is greater than 0, calc steering (otherwise return zero vector)
if (d > 0) {
// normalize desired
desired.normalize();
// two options for magnitude (1 -- based on distance, 2 -- maxspeed)
if ((slowdown) && (d < 100.0f)) desired.mult(maxspeed * (d / 100.0f));
else desired.mult(maxspeed);
// STEERING VECTOR IS DESIREDVECTOR MINUS VELOCITY
steer = Vector3D.sub(desired, vel);
steer.limit(maxforce); // limit to maximum steering force
} else {
steer = new Vector3D(0, 0);
}
return steer;
}
// This constructor could be improved to allow a greater variety of pendulums
Pendul(Vector3D origin_, float r_) {
// Fill all variables
origin = origin_.copy();
r = r_;
theta = 0.0f;
// calculate the location of the ball using polar to cartesian conversion
float x = r * sin(theta);
float y = r * cos(theta);
loc = new Vector3D(origin.x + x, origin.y + y);
theta_vel = 0.0f;
theta_acc = 0.0f;
damping = 0.995f; // Arbitrary damping
ballr = 16.0f; // Arbitrary ball radius
}
// function to display
void render() {
ellipseMode(CENTER);
noStroke();
fill(0, 100, 255, timer);
ellipse(loc.x(), loc.y(), r, r);
}
// function to update location
void update() {
vel.add(acc);
loc.add(vel);
timer -= 1.0f;
}
