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  • What could cause a sudden stop in Box2D?

    - by alexanderpine
    I'm using Box2d for a game, and I have a bug that's driving me nuts. I've simplified the situation down to a square player sliding back and forth frictionlessly on top of a floor composed of a series of square tiles, driven by the left and right keys (which apply a horizontal force). Works great, sliding back and forth across the whole floor. Except... Every once in a while, the player will suddenly stick at the edge of one of the tiles as if it is hitting a (nonexistent) wall. Further pushes in the same direction it was traveling will fail, but as soon as I push backwards once in the opposite direction, I can push forwards past the sticking point again. The sticking point seems to be random, except for being on the edge of a tile. Happens while going left or right. For debugging purposes, I keep the Positions/velocity values for the previous two update ticks and print them out when this stop occurs. As an example, here you see the player moving right, decelerating slightly; pos2 should be about 8.7, but it stops dead instead. tick0: pos= 8.4636 vel= 7.1875 tick1: pos= 8.5816 vel= 7.0833 tick2: pos= 8.5816 vel= 0.0000 So, as the player is 0.8 and the tiles 1.0 wide, the player is stopping just as it is about to cross onto the next tile (8.5816 + 0.8/2 = 8.9816). In fact, I get a collision message (which I ignore except noting that it happened). It only seems to happen at x.5816 (or -x.4184) while moving right, and x.4167 (or -x.5833) while moving left I said that it's like hitting a wall, but in fact, when it hits a wall, the numbers look more like: tick0: pos0= 12.4131 vel2= 8.4375 tick1: pos1= 12.5555 vel1= 8.5417 tick2: pos2= 12.5850 vel0= 0.0000 so it moves further right on the last tick, which puts it in contact with the wall. Anyone seen anything like this. Any suggestion on how I could be causing this behavior.

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  • Transforms in Box2D

    - by user1264811
    I'm attempting to implement a camera in my game. I had it working for regular objects, but I began using Box2D and obviously things changed a bit. I have a Body object that I want to draw at the center of the screen. Basically what I'm doing is subtracting the viewportX and viewportY to the Body. I use this code that currently is not working as it should: public void paint(Graphics2D g, int viewportX, int viewportY) { Transform xf = new Transform(); // m_body is the Body object xf.set(m_body.getTransform()); // Here what I attemp to do is take the transform and alter it // by the viewportX and Y, which is something like **-240, -150**. // Why is it negative? Because an object has coordinates 500, 300 would be displayed // at 160, 150 when the subtraction is done. // With the DrawUtils.toScale(), it's just how I convert the units from JBox2D units // to my units. Vec2 v = Transform.mulTrans(xf, new Vec2(DrawUtils.toScale(-viewportX), DrawUtils.toScale(-viewportY))); // Set the new transform to the new vector. Keep the old angle. xf.set(v, xf.q.getAngle()); g.setColor(Color.white); // I know for a fact that the following method works 100%. It correctly displays // my object, just that it doesn't follow it. for (Fixture f = m_body.getFixtureList(); f != null; f = f.getNext()) DrawUtils.drawShape(f, xf); } Hopefully I didn't over comment this and you understand my problem. I don't want to alter the actual physics position of the object, I just want to display it in the center.

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  • What causes Box2D revolute joints to separate?

    - by nbolton
    I have created a rag doll using dynamic bodies (rectangles) and simple revolute joints (with lower and upper angles). When my rag doll hits the ground (which is a static body) the bodies seem to fidget and the joints separate. It looks like the bodies are sticking to the ground, and the momentum of the rag doll pulls the joint apart (see screenshot below). I'm not sure if it's related, but I'm using the Badlogic GDX Java wrapper for Box2D. Here's some snippets of what I think is the most relevant code: private RevoluteJoint joinBodyParts( Body a, Body b, Vector2 anchor, float lowerAngle, float upperAngle) { RevoluteJointDef jointDef = new RevoluteJointDef(); jointDef.initialize(a, b, a.getWorldPoint(anchor)); jointDef.enableLimit = true; jointDef.lowerAngle = lowerAngle; jointDef.upperAngle = upperAngle; return (RevoluteJoint)world.createJoint(jointDef); } private Body createRectangleBodyPart( float x, float y, float width, float height) { PolygonShape shape = new PolygonShape(); shape.setAsBox(width, height); BodyDef bodyDef = new BodyDef(); bodyDef.type = BodyType.DynamicBody; bodyDef.position.y = y; bodyDef.position.x = x; Body body = world.createBody(bodyDef); FixtureDef fixtureDef = new FixtureDef(); fixtureDef.shape = shape; fixtureDef.density = 10; fixtureDef.filter.groupIndex = -1; fixtureDef.filter.categoryBits = FILTER_BOY; fixtureDef.filter.maskBits = FILTER_STUFF | FILTER_WALL; body.createFixture(fixtureDef); shape.dispose(); return body; } I've skipped the method for creating the head, as it's pretty much the same as the rectangle method (just using a cricle shape). Those methods are used like so: torso = createRectangleBodyPart(x, y + 5, 0.25f, 1.5f); Body head = createRoundBodyPart(x, y + 7.4f, 1); Body leftLegTop = createRectangleBodyPart(x, y + 2.7f, 0.25f, 1); Body rightLegTop = createRectangleBodyPart(x, y + 2.7f, 0.25f, 1); Body leftLegBottom = createRectangleBodyPart(x, y + 1, 0.25f, 1); Body rightLegBottom = createRectangleBodyPart(x, y + 1, 0.25f, 1); Body leftArm = createRectangleBodyPart(x, y + 5, 0.25f, 1.2f); Body rightArm = createRectangleBodyPart(x, y + 5, 0.25f, 1.2f); joinBodyParts(torso, head, new Vector2(0, 1.6f), headAngle); leftLegTopJoint = joinBodyParts(torso, leftLegTop, new Vector2(0, -1.2f), 0.1f, legAngle); rightLegTopJoint = joinBodyParts(torso, rightLegTop, new Vector2(0, -1.2f), 0.1f, legAngle); leftLegBottomJoint = joinBodyParts(leftLegTop, leftLegBottom, new Vector2(0, -1), -legAngle * 1.5f, 0); rightLegBottomJoint = joinBodyParts(rightLegTop, rightLegBottom, new Vector2(0, -1), -legAngle * 1.5f, 0); leftArmJoint = joinBodyParts(torso, leftArm, new Vector2(0, 1), -armAngle * 0.7f, armAngle); rightArmJoint = joinBodyParts(torso, rightArm, new Vector2(0, 1), -armAngle * 0.7f, armAngle);

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  • What causes Box2D revolute joints to separate?

    - by nbolton
    I have created a rag doll using dynamic bodies (rectangles) and simple revolute joints (with lower and upper angles). When my rag doll hits the ground (which is a static body) the bodies seem to fidget and the joints separate. It looks like the bodies are sticking to the ground, and the momentum of the rag doll pulls the joint apart (see screenshot below). I'm not sure if it's related, but I'm using the Badlogic GDX Java wrapper for Box2D. Here's some snippets of what I think is the most relevant code: private RevoluteJoint joinBodyParts( Body a, Body b, Vector2 anchor, float lowerAngle, float upperAngle) { RevoluteJointDef jointDef = new RevoluteJointDef(); jointDef.initialize(a, b, a.getWorldPoint(anchor)); jointDef.enableLimit = true; jointDef.lowerAngle = lowerAngle; jointDef.upperAngle = upperAngle; return (RevoluteJoint)world.createJoint(jointDef); } private Body createRectangleBodyPart( float x, float y, float width, float height) { PolygonShape shape = new PolygonShape(); shape.setAsBox(width, height); BodyDef bodyDef = new BodyDef(); bodyDef.type = BodyType.DynamicBody; bodyDef.position.y = y; bodyDef.position.x = x; Body body = world.createBody(bodyDef); FixtureDef fixtureDef = new FixtureDef(); fixtureDef.shape = shape; fixtureDef.density = 10; fixtureDef.filter.groupIndex = -1; fixtureDef.filter.categoryBits = FILTER_BOY; fixtureDef.filter.maskBits = FILTER_STUFF | FILTER_WALL; body.createFixture(fixtureDef); shape.dispose(); return body; } I've skipped the method for creating the head, as it's pretty much the same as the rectangle method (just using a cricle shape). Those methods are used like so: torso = createRectangleBodyPart(x, y + 5, 0.25f, 1.5f); Body head = createRoundBodyPart(x, y + 7.4f, 1); Body leftLegTop = createRectangleBodyPart(x, y + 2.7f, 0.25f, 1); Body rightLegTop = createRectangleBodyPart(x, y + 2.7f, 0.25f, 1); Body leftLegBottom = createRectangleBodyPart(x, y + 1, 0.25f, 1); Body rightLegBottom = createRectangleBodyPart(x, y + 1, 0.25f, 1); Body leftArm = createRectangleBodyPart(x, y + 5, 0.25f, 1.2f); Body rightArm = createRectangleBodyPart(x, y + 5, 0.25f, 1.2f); joinBodyParts(torso, head, new Vector2(0, 1.6f), headAngle); leftLegTopJoint = joinBodyParts(torso, leftLegTop, new Vector2(0, -1.2f), 0.1f, legAngle); rightLegTopJoint = joinBodyParts(torso, rightLegTop, new Vector2(0, -1.2f), 0.1f, legAngle); leftLegBottomJoint = joinBodyParts(leftLegTop, leftLegBottom, new Vector2(0, -1), -legAngle * 1.5f, 0); rightLegBottomJoint = joinBodyParts(rightLegTop, rightLegBottom, new Vector2(0, -1), -legAngle * 1.5f, 0); leftArmJoint = joinBodyParts(torso, leftArm, new Vector2(0, 1), -armAngle * 0.7f, armAngle); rightArmJoint = joinBodyParts(torso, rightArm, new Vector2(0, 1), -armAngle * 0.7f, armAngle);

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  • Box2D Difference Between WorldCenter and Position

    - by Free Lancer
    So this problem has been brothering for a couple of days now. First off, what is the difference between say Body.getWorldCenter() and Body.getPosition(). I heard that WorldCenter might have to do with the center of gravity or something. Second, When I create a Box2D Body for a sprite the Body is always at the lower left corner. I check it by printing a Rectangle of 1 pixel around the box.getWorldCenter(). From what I understand the Body should be in the center of the Sprite and its bounding box should wrap around the Sprite, correct? Here's an image of what I mean (The Sprite is Red, Body Blue): Here's some code: Body Creator: public static Body createBoxBody( final World pPhysicsWorld, final BodyType pBodyType, final FixtureDef pFixtureDef, Sprite pSprite ) { float pRotation = 0; float pCenterX = pSprite.getX() + pSprite.getWidth() / 2; float pCenterY = pSprite.getY() + pSprite.getHeight() / 2; float pWidth = pSprite.getWidth(); float pHeight = pSprite.getHeight(); final BodyDef boxBodyDef = new BodyDef(); boxBodyDef.type = pBodyType; //boxBodyDef.position.x = pCenterX / Constants.PIXEL_METER_RATIO; //boxBodyDef.position.y = pCenterY / Constants.PIXEL_METER_RATIO; boxBodyDef.position.x = pSprite.getX() / Constants.PIXEL_METER_RATIO; boxBodyDef.position.y = pSprite.getY() / Constants.PIXEL_METER_RATIO; Vector2 v = new Vector2( boxBodyDef.position.x * Constants.PIXEL_METER_RATIO, boxBodyDef.position.y * Constants.PIXEL_METER_RATIO ); Gdx.app.log("@Physics", "createBoxBody():: Box Position: " + v); // Temporary Box shape of the Body final PolygonShape boxPoly = new PolygonShape(); final float halfWidth = pWidth * 0.5f / Constants.PIXEL_METER_RATIO; final float halfHeight = pHeight * 0.5f / Constants.PIXEL_METER_RATIO; boxPoly.setAsBox( halfWidth, halfHeight ); // set the anchor point to be the center of the sprite pFixtureDef.shape = boxPoly; final Body boxBody = pPhysicsWorld.createBody(boxBodyDef); Gdx.app.log("@Physics", "createBoxBody():: Box Center: " + boxBody.getPosition().mul(Constants.PIXEL_METER_RATIO)); boxBody.createFixture(pFixtureDef); boxBody.setTransform( boxBody.getWorldCenter(), MathUtils.degreesToRadians * pRotation ); boxPoly.dispose(); return boxBody; } Making the Sprite: public Car( Texture texture, float pX, float pY, World world ) { super( "Car" ); mSprite = new Sprite( texture ); mSprite.setSize( mSprite.getWidth() / 6, mSprite.getHeight() / 6 ); mSprite.setPosition( pX, pY ); mSprite.setOrigin( mSprite.getWidth()/2, mSprite.getHeight()/2); FixtureDef carFixtureDef = new FixtureDef(); // Set the Fixture's properties, like friction, using the car's shape carFixtureDef.restitution = 1f; carFixtureDef.friction = 1f; carFixtureDef.density = 1f; // needed to rotate body using applyTorque mBody = Physics.createBoxBody( world, BodyDef.BodyType.DynamicBody, carFixtureDef, mSprite ); }

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  • iphone - How do I add videos to iPad simulator?

    - by Mike
    No, dropping the videos to ~/Library/Application Support/iPhone Simulator/3.2/Media/DCIM/100APPLE does not work totally, because the simulator can see the video on Photos.app, but when I try to pick a video using UIImagePickerController my application crashes. I think this may have some relation to the format the video has to have. I am using QuickTime to generate the video. I am using the settings "for iPhone"... so it is generating a M4V with 480x360 pixels H264. I have tried to create a MOV with the same characteristics and one with 640x480 but nothing works. I have also dropped a movie created with iPhone 3GS and it still crashes. this is the error I see when it crashes * Terminating app due to uncaught exception 'NSRangeException', reason: '* -[NSCFArray objectAtIndex:]: index (1) beyond bounds (0)' the method didFinishPickingMediaWithInfo is never called, so its some issue on the simulator or on the video. The app crashes as soon as I pick the video. any ideas? thanks.

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  • Gizmodo Made No Money On Their iPhone 4G Scoop Blog Posts

    - by Gopinath
    Amit Agarwal of Labnol reported couple of days ago that Gizmodo would have made $150,000 from the iPhone 4G scoop that revealed  all the secrets about iPhone 4G. But the reality seems to be entirely different. Gawker Media owner Nick Denton says that "There were no immediate revenue benefits whatsoever — in fact, only costs,"(via businessinsider) Gizmodo paid $5,000 to get hold of iPhone 4G which was lost by an Apple Engineer at a bar after his birthday party. Plus an additional amount of $7000 is spent on keeping the servers up to server 23 page views attracted by the iPhone 4G blog posts. Irrespective of whether Gizmodo made profits or not, they got huge publicity. But at the same time Apple should be very angry with Gizmodo for derailing it’s planned unveiling of the product. We have to wait and see what action Apple is going to take against Gizmodo. Join us on Facebook to read all our stories right inside your Facebook news feed.

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  • Looking For iPhone 4S Alternatives? Here Are 3 Smartphones You Should Consider

    - by Gopinath
    If you going to buy iPhone 4S on a two year contract in USA, Europe or Australia you may not find it expensive. But if you are planning to buy it in any other parts of the world, you will definitely feel the heat of ridiculous iPhone 4S price. In India iPhone 4S costs approximately costs $1000 which is 30% more than the price tag of an unlocked iPhone sold in USA. Personally I love iPhones as there is no match for the user experience provided by Apple as well as the wide range of really meaning applications available for iPhone. But it breaks heart to spend $1000 for a phone and I’m forced to look at alternates available in the market. Here are the four iPhone 4S alternates available in almost all the countries where we can buy iPhone 4S Google Galaxy Nexus The Galaxy Nexus is Google’s own Android smartphone manufactured by Samsung and sold under the brand name of Google Nexus. Galaxy Nexus is the pure Android phone available in the market without any bloat software or custom user interfaces like other Androids available in the market. Galaxy Nexus is also the first Android phone to be shipped with the latest version of Android OS, Ice Cream Sandwich. This phone is the benchmark for the rest of Android phones that are going to enter the market soon. In the words of Google this smartphone is called as “Galaxy Nexus: Simple. Beautiful. Beyond Smart.”.  BGR review summarizes the phone as This is almost comical at this point, but the Samsung Galaxy Nexus is my favourite Android device in the world. Easily replacing the HTC Rezound, the Motorola DROID RAZR, and Samsung Galaxy S II, the Galaxy Nexus champions in a brand new version of Android that pushes itself further than almost any other mobile OS in the industry. Samsung Galaxy S II The one single company that is able to sell more smartphones than Apple is Samsung. Samsung recently displaced Apple from the top smartphone seller spot and occupied it with loads of pride. Samsung’s Galaxy S II fits as one the best alternatives to Apple’s iPhone 4S with it’s beautiful design and remarkable performance. Engadget summarizes Samsung Galaxy S2 review as It’s the best Android smartphone yet, but more importantly, it might well be the best smartphone, period. Of course, a 4.3-inch screen size won’t suit everyone, no matter how stupendously thin the device that carries it may be, and we also can’t say for sure that the Galaxy S II would justify a long-term iOS user foresaking his investment into one ecosystem and making the leap to another. Nonetheless, if you’re asking us what smartphone to buy today, unconstrained by such externalities, the Galaxy S II would be the clear choice. Sometimes it’s just as simple as that. Nokia Lumia 800 Here comes unexpected Windows Phone in to the boxing ring. May be they are not as great as Androids available in the market today, but they are picking up very quickly. Especially the Nokia Lumia 800 seems to be first ever Windows Phone 7 aimed at competing serious with Androids and iPhones available in the market. There are reports that Nokia Lumia 800 is outselling all Androids in UK and few high profile tech blogs are calling it as the king of Windows Phone. Considering this phone while evaluating the alternative of iPhone 4S will not disappoint you. We assure. Droid RAZR Remember the Motorola Driod that swept entire Android market share couple of years ago? The first two version of Motorola Droids were the best in the market and they out performed almost every other Android phone those days. The invasion of Samsung Androids, Motorola lost it charm. With the recent release of Droid RAZR, Motorola seems to be in the right direction to reclaiming the prestige. Droid RAZR is the thinnest smartphone available in the market and it’s beauty is not just skin deep. Here is a review of the phone from Engadget blog the RAZR’s beauty is not only skin deep. The LTE radio, 1.2GHz dual-core processor and 1GB of RAM make sure this sleek number is ready to run with the big boys. It kept pace with, and in some cases clearly outclassed its high-end competition. Despite its deficiencies in the display department and underwhelming battery life, the RAZR looks to be a perfectly viable alternative when considering the similarly-pricey Rezound and Galaxy Nexus Further Reading So we have seen the four alternates of iPhone 4S available in the market and I personally love to buy a Samsung smartphone if I’m don’t have money to afford an iPhone 4S. If you are interested in deep diving into the alternates, here few links that help you do more research Apple iPhone 4S vs. Samsung Galaxy Nexus vs. Motorola Droid RAZR: How Their Specs Compare by Huffington Post Nokia Lumia 800 vs. iPhone 4S vs. Nexus Galaxy: Spec Smackdown by PC World Browser Speed Test: Nokia Lumia 800 vs. iPhone 4S vs. Samsung Galaxy S II – by Gizmodo iPhone 4S vs Samsung Galaxy S II by pocket lint Apple iPhone 4S vs. Samsung Galaxy S II by techie buzz This article titled,Looking For iPhone 4S Alternatives? Here Are 3 Smartphones You Should Consider, was originally published at Tech Dreams. Grab our rss feed or fan us on Facebook to get updates from us.

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  • iPhone: Software Development And Distribution

    - by xsl
    I have a few quick questions about the iPhone software development. I did some research about the topic, but there are a few specific things I would like to ask here, because I will have to estimate the cost of the required hardware and software, before I am allowed to buy anything. I never did any Mac development nor have I ever owned an iPhone, so needless to say this is quite hard for me. I will buy an iMac mini with 2 GB RAM for iPhone development. I will have to use it at the same time as my regular PC, but the majority of the time I won't use the Mac at all. Do I have to buy an additional monitor, a mouse and a keyboard or is there a better solution? I will have to port a C library to the iPhone platform and develop an iPhone application that uses the ported library. Do I need anything else than the iPhone SDK to do this? If I use an external library (see above), can I test the application with the integrated emulator, or is it recommend to buy the device? In a later phase of the project I will have to buy an iPhone, but I will have to wait until the iPhone 4 is released here in Europe, because the application requires a camera. In addition to this I will have to send data to a remote webservice. Aside from these two things I don't require any other features. Can I just buy the iPhone online from another country (the iPhones here are sim locked), or should I buy one with a contract? When the application is ready, it will be installed on a few iPhones owned by our customer. Because of security reasons it is crucial that there is no third party involved in this process (i.e. the application should not be distributed on the app store). Is this possible?

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  • Box2D body rotation with setTransform

    - by thobens
    I' having a problem rotating a body with setTransform(), The body has multiple sensors that should rotate with the player. The rotation works but it rotates around the bodys local 0,0 position instead of the center. Note that the game is in a top-down perspective and the player can go in four different directions, thus I need to rotate him immediately (in one tick) in 90 degrees steps. Up: Down: I can't find a way to set the rotation center. Here's the code I use to rotate it: float angle = direction * 90 * MathUtils.degRad; // direction is an int value from 0 to 3 body.setTransform(body.getPosition(), angle); I also tried body.getLocalCenter().set() and bc.body.getMassData().center.set() but it didn't seem to have any effect. How can I rotate the body around its center?

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  • BOX2D and AS3: Mouse Event not working

    - by Gabriel Meono
    Background: Trying to make a simple "drop the ball" game. The code is located inside the first frame of the timeline. Nothing more is on the stage. Issue: Using QuickBox2D I made a simple If statement that drops and object acording the Mouse-x position: if (MouseEvent.CLICK) { sim.addCircle({x:mouseX, y:1, radius:0.25, density:5}); I imported the MouseEvent library: import flash.events.MouseEvent; Nothing happens if I click, no output errors either. See it in action: http://gabrielmeono.com/download/Lucky_Hit_Alpha.swf http://gabrielmeono.com/download/Lucky_Hit_Alpha.fla Full Code: [SWF(width = 350, height = 600, frameRate = 60)] import com.actionsnippet.qbox.*; import flash.events.MouseEvent; var sim:QuickBox2D = new QuickBox2D(this); sim.createStageWalls(); //var ball:sim.addCircle({x:mouseX, y:1, radius:0.25, density:5}); // // make a heavy circle sim.addCircle({x:3, y:1, radius:0.25, density:5}); sim.addCircle({x:2, y:1, radius:0.25, density:5}); sim.addCircle({x:4, y:1, radius:0.25, density:5}); sim.addCircle({x:5, y:1, radius:0.25, density:5}); sim.addCircle({x:6, y:1, radius:0.25, density:5}); // create a few platforms sim.addBox({x:3, y:2, width:4, height:0.2, density:0, angle:0.1}); // make 26 dominoes for (var i:int = 0; i<7; i++){ //End sim.addCircle({x:1 + i * 1.5, y:16, radius:0.1, density:0}); sim.addCircle({x:2 + i * 1.5, y:15, radius:0.1, density:0}); //Mid end sim.addCircle({x:0 + i * 2, y:14, radius:0.1, density:0}); sim.addCircle({x:0 + i * 2, y:13, radius:0.1, density:0}); sim.addCircle({x:0 + i * 2, y:12, radius:0.1, density:0}); sim.addCircle({x:0 + i * 2, y:11, radius:0.1, density:0}); sim.addCircle({x:0 + i * 2, y:10, radius:0.1, density:0}); //Middle Start sim.addCircle({x:0 + i * 1.5, y:09, radius:0.1, density:0}); sim.addCircle({x:1 + i * 1.5, y:08, radius:0.1, density:0}); sim.addCircle({x:0 + i * 1.5, y:07, radius:0.1, density:0}); sim.addCircle({x:1 + i * 1.5, y:06, radius:0.1, density:0}); } if (MouseEvent.CLICK) { sim.addCircle({x:mouseX, y:1, radius:0.25, density:5}); sim.start(); /*sim.mouseDrag();*/ }

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  • Box2D Static-Dynamic body joint eliminates collisions

    - by andrewz
    I have a static body A, and a dynamic body B, and a dynamic body C. A is filtered to not collide with anything, B and C collide with each other. I wish to create a joint between B and A. When I create a joint (ex. revolute), B no longer collides with C - C passes through it as if it does not exist. What am I doing wrong? How can adding a joint prevent a body from colliding with another body it used to? EDIT: I want to join B with A, and have B collide with C, but not A collide with C. In realistic terms, I'm trying to create a revolute joint between a wheel (B) and a wall (A), and have a box (C) hit the wheel and the wheel would then rotate. EDIT: I create a the simplest revolute joint I can with these parameters (C++): b2RevoluteJointDef def; def.Initialize(A, B, B -> GetWorldCenter()); world -> CreateJoint(&def);

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  • PhysicsMouseJoint problem in andengine + Box2d

    - by Nikhil Lamba
    What we can remove from this code i.e from PhysicsMouseJointExample to remove the functionality of drag and drog of sprite but i need all functionality except this only user move the sprite with some force and velocity of fling but user can't move the ball as like drag and drop like moving a finger on screen and sprite move with finger plz plz help me I am Using Below method for Mouse Joint CODE : public MouseJoint createMouseJoint(final IShape pFace, final float pTouchAreaLocalX, final float pTouchAreaLocalY) { final Body body = (Body) pFace.getUserData(); final MouseJointDef mouseJointDef = new MouseJointDef(); final Vector2 localPoint = Vector2Pool.obtain((pTouchAreaLocalX - pFace.getWidth() * 0.5f) / PhysicsConstants.PIXEL_TO_METER_RATIO_DEFAULT, (pTouchAreaLocalY - pFace.getHeight() * 0.5f) / PhysicsConstants.PIXEL_TO_METER_RATIO_DEFAULT); this.groundBody.setTransform(localPoint, 0); mouseJointDef.bodyA = this.groundBody; mouseJointDef.bodyB = body; mouseJointDef.dampingRatio = 0.95f; mouseJointDef.frequencyHz = 30; mouseJointDef.maxForce = (200.0f * body.getMass()); mouseJointDef.collideConnected = true; mouseJointDef.target.set(body.getWorldPoint(localPoint)); Vector2Pool.recycle(localPoint); return (MouseJoint)mPhysicsWorld.createJoint(mouseJointDef); }

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  • Box2d - Attaching a fired arrow to a moving enemy

    - by Satchmo Brown
    I am firing an arrow from the player to moving enemies. When the arrow hits the enemy, I want it to attach exactly where it hit and cause the enemy (a square) to tumble to the ground. Excluding the logistics of the movement and the spin (it already works), I am stuck on the attaching of the two bodies. I tried to weld them together initially but when they fell, they rotated in opposite directions. I have figured that a revolute joint is probably what I am after. The problem is that I can't figure out a way to attach them right where they collide. Using code from iforce2d: b2RevoluteJointDef revoluteJointDef; revoluteJointDef.bodyA = m_body; revoluteJointDef.bodyB = m_e->m_body; revoluteJointDef.collideConnected = true; revoluteJointDef.localAnchorA.Set(0,0);//the top right corner of the box revoluteJointDef.localAnchorB.Set(0,0);//center of the circle b2RevoluteJoint m_joint = *(b2RevoluteJoint*)m_game->m_world->CreateJoint( &revoluteJointDef ); m_body->SetLinearVelocity(m_e->m_body->GetLinearVelocity()); This attaches them but in the center of both of their points. Does anyone know how I would go about getting the exact point of collision so I can link these? Is this even the right method of doing this? Update: I have the exact point of collision. But I still am not sure this is even the method I want to go about this. Really, I just want to attach body A to B and have body B unaffected in any way.

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  • AndEngine; Box2D - high speed body overlapping, prismatic joints

    - by Visher
    I'm trying to make good suspension for my car game, but I'm getting nervous of some problems with it. At the beginning, I've tried to make it out of one prismatic joint/revolute joint per one wheel only, but surprisingly prismatic joint that should only move in Y asix moves also in X axis, if car travels very fast, or even on low speeds if there's setContinuousPhysics = true. This causes wheels to "shift back", moving them away from axle. Now I've tried to add some bodies that will keep it in place: Suspension helper collides with spring only, wheel doesn't collide with spring&helper&vehicle body This is how I create those elements: rect = new Rectangle(1100, 1350, 200, 50, getVertexBufferObjectManager()); rect.setColor(Color.RED); scene.attachChild(rect); //rect.setRotation(90); Rectangle miniRect1 = new Rectangle(1102, 1355, 30, 50, getVertexBufferObjectManager()); miniRect1.setColor(0, 0, 1, 0.5f); miniRect1.setVisible(true); scene.attachChild(miniRect1); Rectangle miniRect2 = new Rectangle(1268, 1355, 30, 50, getVertexBufferObjectManager()); miniRect2.setColor(0, 0, 1, 0.5f); miniRect1.setVisible(true); scene.attachChild(miniRect2); rectBody = PhysicsFactory.createBoxBody( physicsWorld, rect, BodyDef.BodyType.DynamicBody, PhysicsFactory.createFixtureDef(10.0f, 0.01f, 10.0f)); rectBody.setUserData("car"); Body miniRect1Body = PhysicsFactory.createBoxBody( physicsWorld, miniRect1, BodyDef.BodyType.DynamicBody, PhysicsFactory.createFixtureDef(10.0f, 0.01f, 10.0f)); miniRect1Body.setUserData("suspension"); Body miniRect2Body = PhysicsFactory.createBoxBody( physicsWorld, miniRect2, BodyDef.BodyType.DynamicBody, PhysicsFactory.createFixtureDef(10.0f, 0.01f, 10.0f)); miniRect2Body.setUserData("suspension"); physicsWorld.registerPhysicsConnector(new PhysicsConnector(rect, rectBody, true, true)); physicsWorld.registerPhysicsConnector(new PhysicsConnector(miniRect1, miniRect1Body, true, true)); physicsWorld.registerPhysicsConnector(new PhysicsConnector(miniRect2, miniRect2Body, true, true)); PrismaticJointDef miniRect1JointDef = new PrismaticJointDef(); miniRect1JointDef.initialize(rectBody, miniRect1Body, miniRect1Body.getWorldCenter(), new Vector2(0.0f, 0.3f)); miniRect1JointDef.collideConnected = false; miniRect1JointDef.enableMotor= true; miniRect1JointDef.maxMotorForce = 15; miniRect1JointDef.motorSpeed = 5; miniRect1JointDef.enableLimit = true; physicsWorld.createJoint(miniRect1JointDef); PrismaticJointDef miniRect2JointDef = new PrismaticJointDef(); miniRect2JointDef.initialize(rectBody, miniRect2Body, miniRect2Body.getWorldCenter(), new Vector2(0.0f, 0.3f)); miniRect2JointDef.collideConnected = false; miniRect2JointDef.enableMotor= true; miniRect2JointDef.maxMotorForce = 15; miniRect2JointDef.motorSpeed = 5; miniRect2JointDef.enableLimit = true; physicsWorld.createJoint(miniRect2JointDef); scene.attachChild(karoseriaSprite); Rectangle r1 = new Rectangle(1050, 1300, 52, 150, getVertexBufferObjectManager()); r1.setColor(0, 1, 0, 0.5f); r1.setVisible(true); scene.attachChild(r1); Body r1body = PhysicsFactory.createBoxBody(physicsWorld, r1, BodyDef.BodyType.DynamicBody, PhysicsFactory.createFixtureDef(10.0f, 0.001f, 0.01f)); r1body.setUserData("suspensionHelper"); physicsWorld.registerPhysicsConnector(new PhysicsConnector(r1, r1body, true, true)); WeldJointDef r1jointDef = new WeldJointDef(); r1jointDef.initialize(r1body, rectBody, r1body.getWorldCenter()); physicsWorld.createJoint(r1jointDef); Rectangle r2 = new Rectangle(1132, 1300, 136, 150, getVertexBufferObjectManager()); r2.setColor(0, 1, 0, 0.5f); r2.setVisible(true); scene.attachChild(r2); Body r2body = PhysicsFactory.createBoxBody(physicsWorld, r2, BodyDef.BodyType.DynamicBody, PhysicsFactory.createFixtureDef(10.0f, 0.001f, 0.01f)); r2body.setUserData("suspensionHelper"); physicsWorld.registerPhysicsConnector(new PhysicsConnector(r2, r2body, true, true)); WeldJointDef r2jointDef = new WeldJointDef(); r2jointDef.initialize(r2body, rectBody, r2body.getWorldCenter()); physicsWorld.createJoint(r2jointDef); Rectangle r3 = new Rectangle(1298, 1300, 50, 150, getVertexBufferObjectManager()); r3.setColor(0, 1, 0, 0.5f); r3.setVisible(true); scene.attachChild(r3); Body r3body = PhysicsFactory.createBoxBody(physicsWorld, r3, BodyDef.BodyType.DynamicBody, PhysicsFactory.createFixtureDef(1f, 0.01f, 0.01f)); r3body.setUserData("suspensionHelper"); physicsWorld.registerPhysicsConnector(new PhysicsConnector(r3, r3body, true, true)); WeldJointDef r3jointDef = new WeldJointDef(); r3jointDef.initialize(r3body, rectBody, r3body.getWorldCenter()); physicsWorld.createJoint(r3jointDef); MouseJointDef md = new MouseJointDef(); Sprite wheel1 = new Sprite( miniRect1.getX()+miniRect1.getWidth()/2-wheelTexture.getWidth()/2, miniRect1.getY()+miniRect1.getHeight()-wheelTexture.getHeight()/2, wheelTexture, engine.getVertexBufferObjectManager()); scene.attachChild(wheel1); Body wheel1body = PhysicsFactory.createCircleBody( physicsWorld, wheel1, BodyDef.BodyType.DynamicBody, PhysicsFactory.createFixtureDef(10.0f, 0.01f, 5.0f)); wheel1body.setUserData("wheel"); Shape wheel1shape = wheel1body.getFixtureList().get(0).getShape(); wheel1shape.setRadius(wheel1shape.getRadius()*(3.0f/4.0f)); physicsWorld.registerPhysicsConnector(new PhysicsConnector(wheel1, wheel1body, true, true)); Sprite wheel2 = new Sprite( miniRect2.getX()+miniRect2.getWidth()/2-wheelTexture.getWidth()/2, miniRect2.getY()+miniRect2.getHeight()-wheelTexture.getHeight()/2, wheelTexture, engine.getVertexBufferObjectManager()); scene.attachChild(wheel2); Body wheel2body = PhysicsFactory.createCircleBody( physicsWorld, wheel2, BodyDef.BodyType.DynamicBody, PhysicsFactory.createFixtureDef(10.0f, 0.01f, 5.0f)); wheel2body.setUserData("wheel"); Shape wheel2shape = wheel2body.getFixtureList().get(0).getShape(); wheel2shape.setRadius(wheel2shape.getRadius()*(3.0f/4.0f)); physicsWorld.registerPhysicsConnector(new PhysicsConnector(wheel2, wheel2body, true, true)); RevoluteJointDef frontWheelRevoluteJointDef = new RevoluteJointDef(); frontWheelRevoluteJointDef.initialize(wheel1body, miniRect1Body, wheel1body.getWorldCenter()); frontWheelRevoluteJointDef.collideConnected = false; RevoluteJointDef rearWheelRevoluteJointDef = new RevoluteJointDef(); rearWheelRevoluteJointDef.initialize(wheel2body, miniRect2Body, wheel2body.getWorldCenter()); rearWheelRevoluteJointDef.collideConnected = false; rearWheelRevoluteJointDef.motorSpeed = 2050; rearWheelRevoluteJointDef.maxMotorTorque= 3580; physicsWorld.createJoint(frontWheelRevoluteJointDef); Joint j = physicsWorld.createJoint(rearWheelRevoluteJointDef); rearWheelRevoluteJoint = (RevoluteJoint)j; r1body.setBullet(true); r2body.setBullet(true); r3body.setBullet(true); miniRect1Body.setBullet(true); miniRect2Body.setBullet(true); rectBody.setBullet(true); at low speeds, it's OK, but on high speed vehicle can even flip around on flat ground.. Is there a way to make this work better?

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  • Box2D how to implement a camera?

    - by Romeo
    By now i have this Camera class. package GameObjects; import main.Main; import org.jbox2d.common.Vec2; public class Camera { public int x; public int y; public int sx; public int sy; public static final float PIXEL_TO_METER = 50f; private float yFlip = -1.0f; public Camera() { x = 0; y = 0; sx = x + Main.APPWIDTH; sy = y + Main.APPHEIGHT; } public Camera(int x, int y) { this.x = x; this.y = y; sx = x + Main.APPWIDTH; sy = y + Main.APPHEIGHT; } public void update() { sx = x + Main.APPWIDTH; sy = y + Main.APPHEIGHT; } public void moveCam(int mx, int my) { if(mx >= 0 && mx <= 80) { this.x -= 2; } else if(mx <= Main.APPWIDTH && mx >= Main.APPWIDTH - 80) { this.x += 2; } if(my >= 0 && my <= 80) { this.y += 2; } else if(my <= Main.APPHEIGHT && my >= Main.APPHEIGHT - 80) { this.y -= 2; } this.update(); } public float meterToPixel(float meter) { return meter * PIXEL_TO_METER; } public float pixelToMeter(float pixel) { return pixel / PIXEL_TO_METER; } public Vec2 screenToWorld(Vec2 screenV) { return new Vec2(screenV.x + this.x, yFlip * screenV.y + this.y); } public Vec2 worldToScreen(Vec2 worldV) { return new Vec2(worldV.x - this.x, yFlip * worldV.y - this.y); } } I need to know how to modify the screenToWorld and worldToScreen functions to include the PIXEL_TO_METER scaling.

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  • box2d resize bodies arround point

    - by philipp
    I have a compound object, consisting of a b2Body, vector-graphics and a list polygons which describe the b2body's shapes. This object has its own transformation matrix to centralize the storage of transformations. So far everything is working quiet fine, even scaling works, but not if i scale around a point. In the initialization phase of the object it is scaled around a point. This happens in this order: transform the main matrix transform the vector graphics and the polygons recreate the b2Body After this function ran, the shapes and all the graphics are exactly where they should be, BUT: after the first steps of the b2World the graphical stuff moves away from the body. When I ran the debugger I found out that the position of the body is 0/0 the red dot shows the center of scaling. the first image shows the basic setup and the second the final position of the graphics. This distance stays constant for the rest of the simulation. If I set the position via myBody.SetPosition( sx, sy ); the whole scenario just plays a bit more distant for the origin. Any Idea how to fix this? EDIT:: I came deeper down to the problem and it lies in the fact that i must not scale the transform matrix for the b2body shapes around the center, but set the b2body's position back to the point after scaling. But how can I calculate that point? EDIT 2 :: I came ever deeper down to it, even solved it, but this is a slow solution and i hope that there is somebody who understands what formula I need. assuming to have a set polygons relative to an origin as basis shapes for a b2body: scaling the whole object around a certain point is done in the following steps: i scale everything around the center except the polygons i create a clone of the polygons matrix i scale this clone around the point i calculate dx, dy as difference of clone.tx - original.tx and clone.ty - original.ty i scale the original polygon matrix NOT around the point i recreate the body i create the fixture i set the position of the body to dx and dy done! So what i an interested in is a formula for dx and dy without cloning matrices, scaling the clone around a point, getting dx and dy and finally scale the vertex matrix.

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  • Box2D `ApplyLinearImpulse` is not working whereas `SetLinearVelocity` works

    - by Narek
    I need to mimic jumping behavior for the player in my game. Player consists of two fixtures with circle and rectangle shapes. Rectangle I use to detect ground and it is a sensor. Is some point for jumping I do this: float impulseY = body->GetMass() * PLAYER_JUMPING_VEOCITY / PTM_RATIO * std::sin(PLAYER_JUMPING_ANGLE * PI / 180); body->ApplyLinearImpulse(b2Vec2(0, impulseY), body->GetWorldCenter(), true); and player does not jump. But when I do this: body->SetLinearVelocity(b2Vec2(0, PLAYER_JUMPING_VEOCITY / PTM_RATIO * std::sin(PLAYER_JUMPING_ANGLE * PI / 180))); my player jumps. Also when I change the rectangle shape to be normal (not sensor) shape, its works again. Why? Just in case here are the parameters of my rectangular sensor: b2PolygonShape boxShape; boxShape.SetAsBox(width * 0.5/2/PTM_RATIO, height * 0.2/2/PTM_RATIO, b2Vec2(0, -height * 0.4 /PTM_RATIO), 0); b2FixtureDef boxFixtureDef; boxFixtureDef.friction = 0; boxFixtureDef.restitution = 0; boxFixtureDef.density = 1; boxFixtureDef.isSensor = true; boxFixtureDef.userData = static_cast<void*>(PLAYER_GROUP);

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  • Spawning bullets on command in Box2D

    - by recharge330
    I'm making a simple bullet hell game but I can't figure out how to get my character to shoot. Lets say I have bulletBody and shipBody, how would I continually spawn bulletBodies using the shipBody coordinates. I've tried a function that uses an array of b2bodies and just assigns them the bodydef and fixture but that causes the game to crash. C++ sample code would be best but any help is appreciated. EDIT: It looks like any reference to my b2World in a function will cause the game to crash. How do I declare the bodies without using a b2World as an argument in the function.

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  • Box2d contant speed before and after collision

    - by bobenko
    I want to make my body fly at constant speed, how to make it fly at constant speed before and after collision? I set restitution of my body to 1.0 but after some direct and powerful collisions my objects begins to slow, I want it to fly same speed as before. I heard this can be done by setting liner damping of the object, I think it can prevent only from fast flying objects not slow. Thanks in advance.

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  • Build an iPhone 5 Charging Dock for $1 [DIY Project Video]

    - by Asian Angel
    Are you experiencing frustration since no one has built and released an official charging dock for the iPhone 5 yet? Then this quick little DIY charging dock project may be the perfect solution to your problem and serve as a good ‘hold-over’ until a factory version is released. Build an iPhone 5 dock for $1 [via There I Fixed It - Cheezburger Network] 8 Deadly Commands You Should Never Run on Linux 14 Special Google Searches That Show Instant Answers How To Create a Customized Windows 7 Installation Disc With Integrated Updates

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  • How does one get UI_USER_INTERFACE_IDIOM() to work with iPhone OS SDK < 3.2

    - by drootang
    Apple advises using the following code to detect whether running on an iPad or iPhone/iPod Touch: if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) { // The device is an iPad running iPhone 3.2 or later. // [for example, load appropriate iPad nib file] } else { // The device is an iPhone or iPod touch. // [for example, load appropriate iPhone nib file] } The problem is that UI_USER_INTERFACE_IDIOM() and UIUserInterfaceIdiomPad are NOT defined in the SDKs priory to 3.2. This seems to completely defeat the purpose of such a function. They can only be compiled and run on iPhone OS 3.2 (iPhone OS 3.2 can only be run on iPad). So if you can use UI_USER_INTERFACE_IDIOM(), the result will always be to indicate an iPad. If you include this code and target OS 3.1.3 (the most recent iPhone/iPod Touch OS) in order to test your iPhone-bound universal app code, you will get compiler errors since the symbols are not defined in 3.1.3 or earlier. If this is the recommended-by-Apple approach to runtime device-detection, what am I doing wrong? Has anyone succeeded using this approach to device-detection?

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  • UI_USER_INTERFACE_IDIOM() does not work with iPhone OS SDK < 3.2

    - by drootang
    Apple advises using the following code to detect whether running on an iPad or iPhone/iPod Touch: if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) { // The device is an iPad running iPhone 3.2 or later. // [for example, load appropriate iPad nib file] } else { // The device is an iPhone or iPod touch. // [for example, load appropriate iPhone nib file] } The problem is that UI_USER_INTERFACE_IDIOM() and UIUserInterfaceIdiomPad are NOT defined in the SDKs priory to 3.2. This seems to completely defeat the purpose of such a function. They can only be compiled and run on iPhone OS 3.2 (iPhone OS 3.2 can only be run on iPad). So if you can use UI_USER_INTERFACE_IDIOM(), the result will always be to indicate an iPad. If you include this code and target OS 3.1.3 (the most recent iPhone/iPod Touch OS) in order to test your iPhone-bound universal app code, you will get compiler errors since the symbols are not defined in 3.1.3 or earlier. If this is the recommended-by-Apple approach to runtime device-detection, what am I doing wrong? Has anyone succeeded using this approach to device-detection?

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  • iPhone - How do you make a resizable rectangle for cropping images?

    - by 0SX
    Hi everyone, I'm having a trouble making a re-sizable rectangle for cropping my images. I'm trying to achieve something like this picture: http://img192.imageshack.us/img192/8930/customcropbox.jpg Well, the only problem is I have no clue where to actually start. I need some advice to how I can achieve this effect of cropping. What documentation should I read up on? Core Graphics or Quartz 2d? Both? I've been coding for the iPhone since it's release date but I've never actually used core graphics and etc. Any help or advice would be much appreciated. I'll throw my code up here as I progress to show how it's done when I achieve it. :-) Also, this rectangular box is moveable across the screen in a UIImageView which just makes it more interesting. Thanks for the help and I look forward to achieving this goal.

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