pex-physics-springs

Simple springs physics for Pex library, working with floats, Vec2, and Vec3.

Examples

For use with simple float numbers:

``javascript
var Window = require("pex-sys").Window;
var Platform = require("pex-sys").Platform;
var Canvas = require("omgcanvas");

var Spring = require("pex-physics-springs").Spring;

Window.create({
settings: {
width: 1280,
height: 720,
type: "2d"
},

init: function() {
this.position = new Spring(this.height / 2);

if (Platform.isBrowser) {
this.context = this.canvas.getContext("2d");
}
else {
this.context = new Canvas.CanvasContext(this.canvas);
}

this.on("mouseMoved", function(event) {
this.position.setTarget(event.y);
}.bind(this));
},

draw: function() {
this.position.update();
var current = this.position.getPosition();

this.context.fillRect(0, 0, this.width, this.height);

this.context.beginPath();
this.context.moveTo(0, current);
this.context.lineTo(this.width, current);

this.context.strokeStyle = "white";
this.context.stroke();
}
});
`

For use with Vec2:

`javascript
var Window = require("pex-sys").Window;
var Platform = require("pex-sys").Platform;
var Vec2 = require("pex-geom").Vec2;
var Canvas = require("omgcanvas");

var Spring2 = require("pex-physics-springs").Spring2;

Window.create({
settings: {
width: 1280,
height: 720,
type: "2d"
},

init: function() {
this.position = new Spring2(new Vec2(this.width, this.height).scale(0.5));

if (Platform.isBrowser) {
this.context = this.canvas.getContext("2d");
}
else {
this.context = new Canvas.CanvasContext(this.canvas);
}

this.on("mouseMoved", function(event) {
this.position.setTarget(new Vec2(event.x, event.y));
}.bind(this));
},

draw: function() {
this.position.update();
var current = this.position.getPosition();
var radius = 6;

this.context.fillRect(0, 0, this.width, this.height);
this.context.beginPath();
this.context.arc(current.x, current.y, radius, 0, 2 * Math.PI, false);

this.context.strokeStyle = "white";
this.context.stroke();
}
});
`

Methods

$3

Constructor for spring, arguments:

* position - initial spring position (float/Vec2/Vec3) depending on (Spring/Spring2/Spring3)
* stiffness - spring stiffness
* friction - spring friction
* threshold - spring threshold
* dt - time coefficient, usually 1/30 or 1/60

$3

Resets spring positions, arguments:

* position - new default and current spring position

$3

Sets spring target, arguments:

* position - spring "target", changing this will result in "springiness", if set to null the spring will default to initial position

$3

Returns current spring position.

$3

Returns default (initial) spring position.

$3

Updates spring calculation, should be run in every draw()` in Pex.