demo2-3.html

<html>
   <head>
      <title>Demo1-1 Box2dJS</title>
   </head>
   <body>
      <canvas id="canvas" width="640" height="480" style="background-color:#333333;" ></canvas>
      <script src="js/Box2d.min.js"></script>
      <script>
         function init(){
            var b2Vec2 = Box2D.Common.Math.b2Vec2
            ,b2AABB = Box2D.Collision.b2AABB
            ,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
            ,b2MouseJointDef =  Box2D.Dynamics.Joints.b2MouseJointDef
            ;

            
            var world;
            var worldScale = 30;
            function main(){
               world = new b2World(new b2Vec2(0, 9.81), true);
               var bodyDef = new b2BodyDef(); 
               bodyDef.position.Set(320/worldScale,30/worldScale);
               bodyDef.type = b2Body.b2_dynamicBody;
               var circleShape = new b2CircleShape(25/worldScale);
               var fixtureDef = new b2FixtureDef();
               fixtureDef.shape = circleShape;
               fixtureDef.density = 1;
               fixtureDef.restitution = .6;
               fixtureDef.friction = .1;
               var theBall = world.CreateBody(bodyDef);
               theBall.CreateFixture(fixtureDef);

               // 定义矩形地面
               bodyDef.position.Set(320/worldScale, 470/worldScale); // 复用定义刚体
               bodyDef.type = b2Body.b2_staticBody;
               var polygonShape = new b2PolygonShape();
               polygonShape.SetAsBox(320/worldScale, 10/worldScale);
               fixtureDef.shape = polygonShape; // 复用夹具

               var theFloor = world.CreateBody(bodyDef);
               theFloor.CreateFixture(fixtureDef);

                //setup debug draw
               var debugDraw = new b2DebugDraw();
               debugDraw.SetSprite(document.getElementById("canvas").getContext("2d"));
               debugDraw.SetDrawScale(worldScale);
               debugDraw.SetFillAlpha(0.5);
               debugDraw.SetFlags(b2DebugDraw.e_shapeBit | b2DebugDraw.e_jointBit);
               world.SetDebugDraw(debugDraw);

               setInterval(updateWorld, 1000 / 60);
            }
            function updateWorld() {
               world.Step(1/30,10,10);
               world.ClearForces(); // 清除作用力
               world.DrawDebugData();
            }

            main();
         }
         init();
      </script>
   </body>
</html>