module.exports = Spring;
/**
* Base class for {{#crossLink "LinearSpring"}}{{/crossLink}} and {{#crossLink "RotationalSpring"}}{{/crossLink}}. Not supposed to be used directly.
*
* @class Spring
* @constructor
* @param {Body} bodyA
* @param {Body} bodyB
* @param {Object} [options]
* @param {number} [options.stiffness=100] Spring constant (see Hookes Law). A number >= 0.
* @param {number} [options.damping=1] A number >= 0. Default: 1
* @param {Array} [options.localAnchorA] Where to hook the spring to body A, in local body coordinates. Defaults to the body center.
* @param {Array} [options.localAnchorB]
* @param {Array} [options.worldAnchorA] Where to hook the spring to body A, in world coordinates. Overrides the option "localAnchorA" if given.
* @param {Array} [options.worldAnchorB]
*/
function Spring(bodyA, bodyB, options){
options = options || {};
/**
* Stiffness of the spring.
* @property stiffness
* @type {number}
*/
this.stiffness = options.stiffness !== undefined ? options.stiffness : 100;
/**
* Damping of the spring.
* @property damping
* @type {number}
*/
this.damping = options.damping !== undefined ? options.damping : 1;
/**
* First connected body.
* @property bodyA
* @type {Body}
*/
this.bodyA = bodyA;
/**
* Second connected body.
* @property bodyB
* @type {Body}
*/
this.bodyB = bodyB;
}
/**
* Apply the spring force to the connected bodies. Called automatically by the World.
* @private
* @method applyForce
*/
Spring.prototype.applyForce = function(){
// To be implemented by subclasses
};springs demo
<!DOCTYPE html>
<html>
<head>
<title>Springs demo - p2.js physics engine</title>
<script src="../build/p2.js"></script>
<script src="../build/p2.renderer.js"></script>
<link href="css/demo.css" rel="stylesheet"/>
<meta name="description" content="How to build a spring structure.">
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
</head>
<body>
<script>
// Create demo application
var app = new p2.WebGLRenderer(function(){
var world = new p2.World({
gravity : [0,-5]
});
this.setWorld(world);
world.solver.tolerance = 0.001;
var bodies = [];
var N=10,
M=10,
timeStep = 1/60,
k=1000,
d=10,
l=0.35,
m=1;
var vec2 = p2.vec2;
// Create particle bodies
for(var i=0; i<N; i++){
bodies.push([]);
for(var j=0; j<M; j++){
var p = new p2.Body({
mass: m,//j==M-1 ? 0 : m,
position : [(i-N/2)*l*1.05, (j-M/2)*l*1.05]
});
p.addShape(new p2.Particle());
bodies[i].push(p);
world.addBody(p);
}
}
// Vertical springs
for(var i=0; i<N; i++){
for(var j=0; j<M-1; j++){
var bodyA = bodies[i][j];
var bodyB = bodies[i][j+1];
var spring = new p2.LinearSpring(bodyA,bodyB, {
stiffness: k,
restLength: l,
damping : d
});
world.addSpring(spring);
}
}
// Horizontal springs
for(var i=0; i<N-1; i++){
for(var j=0; j<M; j++){
var bodyA = bodies[i][j];
var bodyB = bodies[i+1][j];
var spring = new p2.LinearSpring(bodyA,bodyB,{
stiffness: k,
restLength: l,
damping : d
});
world.addSpring(spring);
}
}
// Diagonal right/down springs
for(var i=0; i<N-1; i++){
for(var j=0; j<M-1; j++){
var a = bodies[i][j];
var b = bodies[i+1][j+1];
var spring = new p2.LinearSpring(a,b, {
stiffness: k,
restLength: Math.sqrt(l*l + l*l)
});
world.addSpring(spring);
}
}
// Diagonal left/down springs
for(var i=0; i<N-1; i++){
for(var j=0; j<M-1; j++){
var a = bodies[i+1][j];
var b = bodies[i][j+1];
var spring = new p2.LinearSpring(a,b, {
stiffness: k,
restLength: Math.sqrt(l*l + l*l)
});
world.addSpring(spring);
}
}
// Create ground
var planeShape = new p2.Plane();
var plane = new p2.Body({
position : [0, (-M/2)*l*1.05 - 0.1]
});
plane.addShape(planeShape);
world.addBody(plane);
// Create circle
var radius = 1;
var circleShape = new p2.Circle({ radius: radius });
var circle = new p2.Body({
mass : 1,
position : [0, (M/2)*l*1.05 + radius],
angularVelocity:1,
});
circle.addShape(circleShape);
world.addBody(circle);
// Create connected boxes
var box1 = new p2.Body({
mass : 1,
position : [-3, (M/2)*l*1.05 + radius],
});
var box2 = new p2.Body({
mass : 1,
position : [-4, (M/2)*l*1.05 + radius],
angularVelocity : -2
});
box1.addShape(new p2.Box({ width: radius, height: radius }));
box2.addShape(new p2.Box({ width: radius, height: radius }));
world.addBody(box1);
world.addBody(box2);
var s = new p2.LinearSpring(box1, box2, {
restLength : 1,
stiffness : 10,
localAnchorA : [0,0.5],
localAnchorB : [0,0.5],
});
world.addSpring(s);
// Create capsule
var capsuleShape = new p2.Capsule({ length: 1, radius: 0.25 });
var capsuleBody = new p2.Body({
mass: 1,
position : [4,1]
});
capsuleBody.addShape(capsuleShape);
world.addBody(capsuleBody);
var s = new p2.LinearSpring(capsuleBody, plane, {
restLength : 1,
stiffness : 10,
localAnchorA : [-capsuleShape.length/2,0],
worldAnchorB : [4-capsuleShape.length/2,2],
});
world.addSpring(s);
// Create capsules connected with angular spring
var capsuleShapeA = new p2.Capsule({ length: 1, radius: 0.2 });
var capsuleShapeB = new p2.Capsule({ length: 1, radius: 0.2 });
var capsuleBodyA = new p2.Body({
mass: 1,
position : [5,0]
});
var capsuleBodyB = new p2.Body({
mass: 1,
position : [6,0]
});
capsuleBodyA.addShape(capsuleShapeA);
capsuleBodyB.addShape(capsuleShapeB);
world.addBody(capsuleBodyA);
world.addBody(capsuleBodyB);
rotationalSpring = new p2.RotationalSpring(capsuleBodyA, capsuleBodyB, {
stiffness : 10,
damping: 0.01
});
world.addSpring(rotationalSpring);
var revolute = new p2.RevoluteConstraint(capsuleBodyA, capsuleBodyB, {
localPivotA: [0.5, 0],
localPivotB: [-0.5, 0],
collideConnected:false
});
world.addConstraint(revolute);
this.frame(3,0,8,8);
});
</script>
</bodyBody>
</html>Link
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