function path(path){
ctx.beginPath();
var i = 0;
ctx.moveTo(path[i][0],path[i++][1]);
while(i < path.length){
ctx.lineTo(path[i][0],path[i++][1]);
}
if(close){
ctx.closePath();
}
ctx.stroke();
}
function strokeCircle(x,y,r){
ctx.beginPath();
ctx.moveTo(x + r,y);
ctx.arc(x,y,r,0,Math.PI * 2);
ctx.stroke();
}
function display() {
ctx.setTransform(1, 0, 0, 1, 0, 0); // reset transform
ctx.globalAlpha = 1; // reset alpha
ctx.clearRect(0, 0, w, h);
var cx = w/2;
var cy = h/2;
var r1 = Math.abs(Math.sin(globalTime/ 4000) * w / 4);
var r2 = Math.abs(Math.sin(globalTime/ 4300) * h / 4);
var ang = globalTime / 1500;
// find the intercept from ellipse center to mouse on the ellipse
var ratio = r1 / r2
var dx = mouse.x - cx;
var dy = mouse.y - cy;
var dist = Math.hypot(dx,dy);
var ex = Math.cos(-ang);
var ey = Math.sin(-ang);
var c = Math.atan2((dx * ey + dy * ex) * ratio, dx * ex - dy * ey);
var nx = Math.cos(c) * r1;
var ny = Math.sin(c) * r2;
var ix = nx * ex + ny * ey;
var iy = -nx * ey + ny * ex;
var dist = Math.hypot(dx,dy);
var dist2Inter = Math.hypot(ix,iy);
ctx.strokeStyle = "Blue";
ctx.lineWidth = 4;
ctx.beginPath();
ctx.ellipse(cx,cy,r1,r2,ang,0,Math.PI * 2,true)
ctx.stroke();
if(dist2Inter > dist){
ctx.fillStyle = "#7F7";
ctx.globalAlpha = 0.5;
ctx.fill();
ctx.globalAlpha = 1;
}
// Display the intercept
ctx.strokeStyle = "black";
ctx.lineWidth = 2;
path([[cx,cy],[mouse.x,mouse.y]])
ctx.strokeStyle = "red";
ctx.lineWidth = 5;
path([[cx,cy],[cx + ix,cy+iy]])
ctx.strokeStyle = "red";
ctx.lineWidth = 4;
strokeCircle(cx + ix, cy + iy, 6)
ctx.fillStyle = "white";
ctx.fill();
ctx.strokeStyle = "red";
ctx.lineWidth = 4;
strokeCircle(cx, cy, 6)
ctx.fillStyle = "white";
ctx.fill();
ctx.strokeStyle = "black";
ctx.lineWidth = 2;
strokeCircle(mouse.x, mouse.y, 4)
ctx.fillStyle = "white";
ctx.fill();
}
/** SimpleFullCanvasMouse.js begin **/
//==============================================================================
// Boilerplate code from here down and not related to the answer
//==============================================================================
var w, h, cw, ch, canvas, ctx, mouse, globalTime = 0, firstRun = true;
;(function(){
const RESIZE_DEBOUNCE_TIME = 100;
var createCanvas, resizeCanvas, setGlobals, resizeCount = 0;
createCanvas = function () {
var c,
cs;
cs = (c = document.createElement("canvas")).style;
cs.position = "absolute";
cs.top = cs.left = "0px";
cs.zIndex = 1000;
document.body.appendChild(c);
return c;
}
resizeCanvas = function () {
if (canvas === undefined) {
canvas = createCanvas();
}
canvas.width = innerWidth;
canvas.height = innerHeight;
ctx = canvas.getContext("2d");
if (typeof setGlobals === "function") {
setGlobals();
}
if (typeof onResize === "function") {
if(firstRun){
onResize();
firstRun = false;
}else{
resizeCount += 1;
setTimeout(debounceResize, RESIZE_DEBOUNCE_TIME);
}
}
}
function debounceResize() {
resizeCount -= 1;
if (resizeCount <= 0) {
onResize();
}
}
setGlobals = function () {
cw = (w = canvas.width) / 2;
ch = (h = canvas.height) / 2;
}
mouse = (function () {
function preventDefault(e) {
e.preventDefault();
}
var mouse = {
x : 0,
y : 0,
w : 0,
alt : false,
shift : false,
ctrl : false,
buttonRaw : 0,
over : false,
bm : [1, 2, 4, 6, 5, 3],
active : false,
bounds : null,
crashRecover : null,
mouseEvents : "mousemove,mousedown,mouseup,mouseout,mouseover,mousewheel,DOMMouseScroll".split(",")
};
var m = mouse;
function mouseMove(e) {
var t = e.type;
m.bounds = m.element.getBoundingClientRect();
m.x = e.pageX - m.bounds.left;
m.y = e.pageY - m.bounds.top;
m.alt = e.altKey;
m.shift = e.shiftKey;
m.ctrl = e.ctrlKey;
if (t === "mousedown") {
m.buttonRaw |= m.bm[e.which - 1];
} else if (t === "mouseup") {
m.buttonRaw &= m.bm[e.which + 2];
} else if (t === "mouseout") {
m.buttonRaw = 0;
m.over = false;
} else if (t === "mouseover") {
m.over = true;
} else if (t === "mousewheel") {
m.w = e.wheelDelta;
} else if (t === "DOMMouseScroll") {
m.w = -e.detail;
}
if (m.callbacks) {
m.callbacks.forEach(c => c(e));
}
if ((m.buttonRaw & 2) && m.crashRecover !== null) {
if (typeof m.crashRecover === "function") {
setTimeout(m.crashRecover, 0);
}
}
e.preventDefault();
}
m.addCallback = function (callback) {
if (typeof callback === "function") {
if (m.callbacks === undefined) {
m.callbacks = [callback];
} else {
m.callbacks.push(callback);
}
}
}
m.start = function (element) {
if (m.element !== undefined) {
m.removeMouse();
}
m.element = element === undefined ? document : element;
m.mouseEvents.forEach(n => {
m.element.addEventListener(n, mouseMove);
});
m.element.addEventListener("contextmenu", preventDefault, false);
m.active = true;
}
m.remove = function () {
if (m.element !== undefined) {
m.mouseEvents.forEach(n => {
m.element.removeEventListener(n, mouseMove);
});
m.element.removeEventListener("contextmenu", preventDefault);
m.element = m.callbacks = undefined;
m.active = false;
}
}
return mouse;
})();
// Clean up. Used where the IDE is on the same page.
var done = function () {
window.removeEventListener("resize", resizeCanvas)
mouse.remove();
document.body.removeChild(canvas);
canvas = ctx = mouse = undefined;
}
function update(timer) { // Main update loop
if(ctx === undefined){ return; }
globalTime = timer;
display(); // call demo code
requestAnimationFrame(update);
}
setTimeout(function(){
resizeCanvas();
mouse.start(canvas, true);
//mouse.crashRecover = done;
window.addEventListener("resize", resizeCanvas);
requestAnimationFrame(update);
},0);
})();
/** SimpleFullCanvasMouse.js end **/
