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class Point | |
constructor: (@x = 0, @y = 0) -> | |
if isNaN(@x) or isNaN(@y) | |
throw new Error('Invalid coords') | |
add: (point) -> | |
@x += point.x | |
@y += point.y | |
subtract: (point) -> | |
@x -= point.x | |
@y -= point.y | |
scale: (multiplier) -> | |
@x *= multiplier | |
@y *= multiplier | |
min: (x, y) -> | |
@x = x if @x < x | |
@y = y if @y < y | |
max: (x, y) -> | |
@x = x if @x > x | |
@y = y if @y > y | |
replace: (point) -> | |
@x = point.x | |
@y = point.y | |
dup: -> | |
new @constructor(@x, @y) | |
class Force extends Point | |
class Particle | |
constructor: (x = 0, y = 0) -> | |
@current = new Point(x, y) | |
@previous = new Point(x, y) | |
@force = new Point | |
step: (timeStep) -> | |
@verlet(timeStep) | |
@constrain() | |
render: -> | |
setForce: (@force) -> | |
getCoords: -> | |
[@current.x, @current.y] | |
moveTo: (x, y) -> | |
@current.x = x if x? | |
@current.y = y if y? | |
# Private | |
verlet: (timeStep = 0.6) -> | |
calcPoint = new Point(0, 0) | |
tempPoint = @current.dup() | |
forcePoint = @force.dup() | |
forcePoint.scale(timeStep * timeStep) | |
calcPoint.add(@current) | |
calcPoint.subtract(@previous) | |
calcPoint.add(forcePoint) | |
@current.add(calcPoint) | |
@previous.replace(tempPoint) | |
constrain: -> | |
class Element | |
constructor: (@x = 0, | |
@y = 0, | |
@width = 50, | |
@height = 50) -> | |
@particle = new Particle(x, y) | |
setForce: (force) -> | |
@particle.setForce(force) | |
step: (timeStep) -> | |
@particle.step(timeStep) | |
@constrain() | |
moveTo: (x, y) -> | |
@particle.moveTo(x, y) | |
render: (ctx) -> | |
[@x, @y] = @particle.getCoords() | |
ctx.moveTo(@x, @y) | |
@paint(ctx) | |
# Override these | |
constrain: -> | |
paint: (ctx) -> throw 'Must implement paint()' | |
class Rectangle extends Element | |
paint: (ctx) -> | |
ctx.fillStyle = "rgb(200,0,0)" | |
ctx.fillRect(@x, @y, @width, @height) | |
class Stage | |
constructor: -> | |
@el = document.createElement('canvas') | |
@el.width = 300 | |
@el.height = 300 | |
@ctx = @el.getContext('2d') | |
@particles = [] | |
@forces = [] | |
run: => | |
@tick() | |
window.requestAnimationFrame(@run) | |
addElement: (element) => | |
@particles.push(element) | |
addParticle: (push) => | |
@particles.push(particle) | |
addForce: (force) => | |
@forces.push(force) | |
# Private | |
tick: => | |
@step() | |
@render() | |
step: => | |
force = new Point | |
force.add(f) for f in @forces | |
for particle in @particles | |
particle.setForce(force) | |
particle.step() | |
render: => | |
@reset() | |
for particle in @particles | |
@ctx.save() | |
particle.render(@ctx) | |
@ctx.restore() | |
reset: => | |
@ctx.clearRect(0, 0, @el.width, @el.height) | |
@CanvasPhysics = | |
Stage: Stage | |
Point: Point | |
Force: Force | |
Particle: Particle | |
Element: Element | |
Rectangle: Rectangle |
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<!DOCTYPE html> | |
<html> | |
<head> | |
<script src="lib/canvas.physics.js"></script> | |
</head> | |
<body> | |
<div id="app"></div> | |
<script> | |
var stage = new CanvasPhysics.Stage; | |
stage.addForce(new CanvasPhysics.Force(0, 0.9)); // Gravity | |
stage.addElement(new CanvasPhysics.Rectangle); | |
app.appendChild(stage.el); | |
stage.run(); | |
</script> | |
</body> | |
</html> |
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