How to use "applyforce" to blow the objects into direction?
i'm learning box2dweb with html5, and i'm trying to use applyforce to
objects when the circle and square almost near the ground, how to do that?
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>test</title>
<script type="text/javascript" src="box2d/Box2dWeb-2.1.a.3.min.js"></script>
<script type="text/javascript">
var world;
function init() {
var b2Vec2 = Box2D.Common.Math.b2Vec2
, b2BodyDef = Box2D.Dynamics.b2BodyDef
, b2Body = Box2D.Dynamics.b2Body
, b2FixtureDef = Box2D.Dynamics.b2FixtureDef
, b2Fixture = Box2D.Dynamics.b2Fixture
, b2World = Box2D.Dynamics.b2World
, b2MassData = Box2D.Collision.Shapes.b2MassData
, b2PolygonShape = Box2D.Collision.Shapes.b2PolygonShape
, b2CircleShape = Box2D.Collision.Shapes.b2CircleShape
, b2DebugDraw = Box2D.Dynamics.b2DebugDraw
;
world = new b2World(
new b2Vec2(0, 10) //gravity
, true //allow sleep
);
var fixDef = new b2FixtureDef;
fixDef.density = 1.0;
fixDef.friction = 0.5;
fixDef.restitution = 0.2;
var bodyDef = new b2BodyDef;
//create ground
bodyDef.type = b2Body.b2_staticBody;
bodyDef.position.x = 9;
bodyDef.position.y = 13;
fixDef.shape = new b2PolygonShape;
fixDef.shape.SetAsBox(10, 0.5);
world.CreateBody(bodyDef).CreateFixture(fixDef);
//create some objects
bodyDef.type = b2Body.b2_dynamicBody;
for(var i = 0; i < 10; ++i) {
if(Math.random() > 0.5) {
fixDef.shape = new b2PolygonShape;
fixDef.shape.SetAsBox(
Math.random() + 0.1 //half width
, Math.random() + 0.1 //half height
);
} else {
fixDef.shape = new b2CircleShape(
Math.random() + 0.1 //radius
);
}
bodyDef.position.x = Math.random() * 10;
bodyDef.position.y = Math.random() * 30;
var direction = new b2Vec2(-5,0);
world.ApplyForce( direction , world.GetPosition() );
world.CreateBody(bodyDef).CreateFixture(fixDef);
}
//setup debug draw
var debugDraw = new b2DebugDraw();
debugDraw.SetSprite(document.getElementById("canvas").getContext("2d"));
debugDraw.SetDrawScale(30.0);
debugDraw.SetFillAlpha(0.3);
debugDraw.SetLineThickness(1.0);
debugDraw.SetFlags(b2DebugDraw.e_shapeBit |
b2DebugDraw.e_jointBit);
world.SetDebugDraw(debugDraw);
window.setInterval(update, 1000 / 60);
};
function update() {
world.Step(
1 / 60 //frame-rate
, 10 //velocity iterations
, 10 //position iterations
);
world.DrawDebugData();
world.ClearForces();
};
</script>
</head>
<body onLoad="init();">
<canvas id="canvas" width="600" height="400"></canvas>
</body>
</html>
the above code is the example from official web, i've added
var direction = new b2Vec2(-5,0);
world.ApplyForce( direction , world.GetPosition() );
there is an error
Uncaught TypeError: Object # has no method 'GetPosition'
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