Erin Fuller – Turtle Composition

//Erin Fuller
//SectionA
//efuller@andrew.cmu.edu
//Project 11

var t = [0, 1, 2]; //start w/ 3 turtles
var targetX = 0;

function setup() {
    createCanvas(480, 480);
    background(0);
    for (var i = 0; i < t.length; i++) { //initialize turtles
    	t[i] = makeTurtle(0, height / 2 + random(-100, 100));
	    t[i].setColor(color(random(100), random(255), random(255), 50));
	}
	frameRate(40); //slow down turtle!!!
}

function draw() {
    targetX += 1; //updates target with each frame
    var targetY = (width / 2) - 90 * sin(radians(targetX)); //sine wave

    noStroke(); //makes target curve "invisible"
    point(targetX, targetY);

    for (var j = 0; j < t.length; j++) {
	    t[j].penDown();
	    t[j].setWeight(4);  

    	t[j].forward(1.5); 
    	t[j].turnToward(targetX, targetY, 2); //orient towards sine wave
    	t[j].left(random(-5, 5)); //adds noise

    	if (targetX === width) { //restarts when reachinf edge of screen
    		targetX = 0; //restart target
    		for (var k = 0; k < t.length; k++) {
    			t[k].penUp(); //stops turtles moves them back
    			t[k].goto(0, height / 2 + random(-100, 100));
    			t[k].penDown(); //restart turtle
    		}
    	}
    }
}

function mousePressed() {
	var newTurtle = makeTurtle(mouseX,mouseY); //making new turtle at mouse press
	newTurtle.setColor(color(random(100), random(255), random(255), 50));
	t.push(newTurtle); //push turtle onto array
}


//------------------------------------------------------------------------------------  

// makeTurtle(x, y) -- make a turtle at x, y, facing right, pen down
// left(d) -- turn left by d degrees
// right(d) -- turn right by d degrees
// forward(p) -- move forward by p pixels
// back(p) -- move back by p pixels
// penDown() -- pen down
// penUp() -- pen up
// goto(x, y) -- go straight to this location
// setColor(color) -- set the drawing color
// setWeight(w) -- set line width to w
// face(d) -- turn to this absolute direction in degrees
// angleTo(x, y) -- what is the angle from my heading to location x, y?
// turnToward(x, y, d) -- turn by d degrees toward location x, y
// distanceTo(x, y) -- how far is it to location x, y?

function turtleLeft(d) {
    this.angle -= d;
}

function turtleRight(d) {
    this.angle += d;
}

function turtleForward(p) {
    var rad = radians(this.angle);
    var newx = this.x + cos(rad) * p;
    var newy = this.y + sin(rad) * p;
    this.goto(newx, newy);
}

function turtleBack(p) {
    this.forward(-p);
}

function turtlePenDown() {
    this.penIsDown = true;
}

function turtlePenUp() {
    this.penIsDown = false;
}

function turtleGoTo(x, y) {
    if (this.penIsDown) {
      stroke(this.color);
      strokeWeight(this.weight);
      line(this.x, this.y, x, y);
    }
    this.x = x;
    this.y = y;
}

function turtleDistTo(x, y) {
    return sqrt(sq(this.x - x) + sq(this.y - y));
}

function turtleAngleTo(x, y) {
    var absAngle = degrees(atan2(y - this.y, x - this.x));
    var angle = ((absAngle - this.angle) + 360) % 360.0;
    return angle;
}

function turtleTurnToward(x, y, d) {
    var angle = this.angleTo(x, y);
    if (angle < 180) {
        this.angle += d;
    } else {
        this.angle -= d;
    }
}

function turtleSetColor(c) {
    this.color = c;
}

function turtleSetWeight(w) {
    this.weight = w;
}

function turtleFace(angle) {
    this.angle = angle;
}

function makeTurtle(tx, ty) {
    var turtle = {x: tx, y: ty,
                  angle: 0.0, 
                  penIsDown: true,
                  color: color(128),
                  weight: 1,
                  left: turtleLeft, right: turtleRight,
                  forward: turtleForward, back: turtleBack,
                  penDown: turtlePenDown, penUp: turtlePenUp,
                  goto: turtleGoTo, angleto: turtleAngleTo,
                  turnToward: turtleTurnToward,
                  distanceTo: turtleDistTo, angleTo: turtleAngleTo,
                  setColor: turtleSetColor, setWeight: turtleSetWeight,
                  face: turtleFace};
    return turtle;
}

My composition is three turtles chasing a sine wave, but the turtles can never catch it fully because of added noise that makes them wander off track. If you click your mouse, you add a new turtle!