In this simple program, we animate an ellipse to always chase a point defined by the mouse. The ellipse only ever moves a percentage of the distance between it and the target destination in each step. The p5.Vector object is used to handle the coordinates and the simple math operations.
Exercise
Add an additional ellipse that follows the mouse at a slower rate than the first ellipse.
Modify the code so that the ellipse always follows the mouse position.
Replace with the ellipse with another shape (like a triangle or even a car) , and keep it pointed towards the mouse.
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var pos;
var targetPos;
var mousePos;
function setup() {
createCanvas(1000, 600);
fill(0);
pos = createVector(0, 0);
targetPos = createVector(0, 0);
mousePos = createVector(width/2, height/2);
}
function draw() {
background(255);
targetPos.set(mousePos);
targetPos.sub(pos); // find the vector between mouse position and ellipse position
targetPos.mult(0.2); // each step in the animation will move this percentage of the distance to the target position
pos.add(targetPos);
ellipse(pos.x, pos.y, 60, 60);
}
function mousePressed() {
mousePos.set(mouseX, mouseY);
}
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Exercise
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Exercise Solution Using Arrays
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var pos = [];
var targetPos = [];
var mousePos = [];
var arrayLength = 5;
function setup() {
createCanvas(1000, 600);
fill(0);
for (var i = 0; i< arrayLength; i++) {
pos[i] = createVector(0, 0);
targetPos[i] = createVector(0, 0);
}
mousePos = createVector(width/2, height/2);
}
function draw() {
mousePos.set(mouseX, mouseY);
background(255);
for (var i = 0; i < pos.length; i++) {
targetPos[i].set(mousePos);
targetPos[i].sub(pos[i]); // find the vector between mouse position and ellipse position
targetPos[i].mult((i*0.02) + 0.05); // each step in the animation will move this percentage of the distance to the target position
pos[i].add(targetPos[i]);
fill(125,255,23);
ellipse(pos[i].x, pos[i].y, 60, 60);
}
}
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Exercise Solution Using Arrays and
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Objects
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let shape = [];
var arrayLength = 60;
function setup() {
createCanvas(1000, 600);
fill(0);
for (var i= 0; i < arrayLength; i++) {
shape[i] = new myShape((i*0.02) + 0.02);
}
}
function draw() {
background(255);
for (var i= 0; i < shape.length; i++) {
shape[i].update();
}
}
class myShape {
constructor(_speed) {
this.pos = createVector(0,0);
this.targetPos = createVector(0,0);
this.mousePos = createVector(width/2, height/2);
this.speed = _speed;
}
update() {
this.mousePos.set(mouseX, mouseY);
this.targetPos.set(this.mousePos);
this.targetPos.sub(this.pos); // find the vector between mouse position and ellipse position
this.targetPos.mult(this.speed); // each step in the animation will move this percentage of the distance to the target position
this.pos.add(this.targetPos);
pushMatrix();
translate(this.pos.x, this.pos.y);
rotate(calcAngle(this.pos, this.mousePos));
triangle(0,0,-5,20,5,20);
popMatrix();
}
calcAngle(p1, p2)
{
return -atan2(p1.x - p2.x,p1.y - p2.y);
}
}
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