{"id":317,"date":"2009-06-15T23:20:12","date_gmt":"2009-06-16T06:20:12","guid":{"rendered":"https:\/\/actionsnippet.com\/?p=1538"},"modified":"2009-06-15T23:20:12","modified_gmt":"2009-06-16T06:20:12","slug":"quickbox2d-frim","status":"publish","type":"post","link":"https:\/\/actionsnippet.com\/?p=317","title":{"rendered":"QuickBox2D FRIM"},"content":{"rendered":"
\r\nimport com.actionsnippet.qbox.*;\r\nimport Box2D.Common.Math.*;\r\n\r\n\/\/ try altering your frame rate\r\n[SWF(backgroundColor=0x000000, width=700, height=600, frameRate=30)]\r\n\/\/ try setting frim to false\r\nvar sim:QuickBox2D = new QuickBox2D(this, {iterations:20, timeStep:1 \/ 60, frim:true});\r\n\r\nsim.setDefault({fillColor:0x003366, lineAlpha:0});\r\nsim.createStageWalls();\r\n\r\nsim.addBox({x:10, y:18, height:3, density:0});\r\n\r\nsim.setDefault({fillColor:0x004466, lineColor:0x2B80F5});\r\n\r\nvar cVel:b2Vec2 = new b2Vec2();\r\n\r\nfor (var i:int = 0; i<32; i++){\r\n\tvar c:QuickObject = sim.addCircle({x:13 + i % 8, y:10 + int(i \/ 8), friction:0.01, radius:0.2 + Math.random()*0.3, angularDamping:1});\r\n\tcVel.x = Math.random() * 4 - 2;\r\n\tcVel.y = Math.random() * 4 - 2;\r\n\tc.body.SetLinearVelocity(cVel);\r\n}\r\n\r\nvar box:QuickObject = sim.addBox({x:3, y:16, width:2, height: 2});\r\nvar boxVel:b2Vec2 = new b2Vec2(15, -25);\r\n\r\nsim.start();\r\n\r\n\/\/ shoot the box from left to right\r\nsetTimeout(positionBox, 200);\r\nfunction positionBox():void{\r\n\t\/\/ reset box position\r\n\tbox.x = 3, box.y = 16;\r\n\tsetTimeout(shootBox, 500);\r\n}\r\nfunction shootBox():void{\r\n\tbox.body.SetLinearVelocity(boxVel);\r\n\tbox.body.SetAngularVelocity(10);\r\n\t\/\/ shoot the box again\r\n\tsetTimeout(positionBox, 4000);\r\n}\r\n<\/pre>\n
You’ll need to download the latest version of QuickBox2D<\/a> in order to run this snippet (alpha 107 as of this post). I recommend checking out the demo below first though…<\/p>\n
The most notable feature of this release is FRIM (frame rate independent motion). FRIM is used to attempt to keep the speed of the Box2D simulation constant no matter what frame rate the swf is running at. This is good because frame rates will vary from browser to browser and from computer to computer. <\/p>\n
Mr.Doob<\/a> suggested that I implement this feature in QuickBox2D. If you haven’t seen his site<\/a> I highly recommend checking it out – really great stuff there.<\/p>\n
I created a demo to illustrate the FRIM feature… this demo is basically the same as the above snippet with a few extra buttons added to control frame rate and toggle FRIM.<\/p>\n

\nTake a look at the demo here…<\/p>\n
<\/a>