Questions tagged [box2d]

Box2D is an open-source rigid-body 2D physics simulation library for games, written in C++, with ports in various languages

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3answers
110 views

Finding an angle between two bodies

I am trying to find angle between vectors a and b. But the cosine for some reason is not within +/- 1, that means that it is not possible to find an angle between a car and a pedestrian... Any help ...
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1answer
223 views

What scaling system to use in Box2d?

I'm worried about this Caution box from the Box2d manual: Box2D is tuned for MKS units. Keep the size of moving objects roughly between 0.1 and 10 meters. You'll need to use some scaling system ...
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1answer
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how to apply force/impulse perpendicular to the moving direction in box2d

How can i apply or impulse to an object perpendicular to its moving direction in a top down game. Like if object is moving up, i press left or right, then force or impulse should be applied to left or ...
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How do I destroy a Box2D body on contact without getting an IsLocked assertion error?

I get this error when attempting to remove a body from the world: java: /var/lib/hudson/jobs/libgdx/workspace/trunk/gdx/jni/Box2D/Dynamics/b2World.cpp:134: void b2World::DestroyBody(b2Body*): ...
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How to limit Box2D bodies to only be affected on 1 axis

I have a side scrolling game, where I am randomly placing trees, bushes etc.. I would like these bodies to fall ( To Align with the ground ) but not to slide. What is the best way to achieve this and ...
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0answers
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Rolling a circle around a square

I am stuck on a simple Box2D task. I have a box and a ball (in top-down view so no gravity), and I would like the ball to roll around the box. Here is my code. Basically now I am trying to detect ...
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2answers
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Having trouble implementing libGDX pause

I tried to make pause button. When users click Pause button on a screen, a window came out then, game is frozen until users press continue button in the window . my code is able to pop up window, ...
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0answers
338 views

How to make a top down 2D ball rolling

I am developing a top down game similar to 8 pool billard with libgdx and box2d. How do i make a 2d ball texture look like its rolling when force is applied like this: So it feels actually 3d ? For ...
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0answers
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Game runs at different speeds in Chrome versus Firefox

I am using Box2D for physics on the server side. Player position is updated on the server, so there is nothing the client can do except give input. But running game in Chrome only, the player moves ...
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1answer
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Box2D Weird collision behavior

I'll let the gif speak first. As you can see, the small cube just kinda floats there like it has a forcefield. This weird glitch only happens with small cubes, smaller than 60 pixels for some reason. ...
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2answers
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What does linearDamping mean in Box2D?

If I set linearDamping on a body, it's velocity will be decreased slowly, until it stops. The documentation says, that the units are 1/time, which is unclear for me. If the velocity of a body is 10 m/...
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1answer
1k views

Why might a body suddenly stop while moving on continue platform?

I have a 32x32 sprite and I make some to be platform like this ...
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How to fix the sprite that is not drawn on the same position as its body after implementing pixels-per-meter Division?

I had a problem where the sprite was not positioned on Body correctly which I solved and you can see it here. After I solved that, I needed to divide everything by PIXELS PER METERS so that I can ...
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1answer
2k views

How to create a projectile motion of a cannonball in top down view?

Objective To move the bullet with projectile motion to specific destination by touch point. In the below image is an example of a bullet which has a projectile motion. On my observation, the bullet ...
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0answers
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Dealing with ghost vertices of Kinematic bodies in Box2D

I'm using LibGDX and Box2D and I want to have multiple falling platforms in a row which will fall sequentially as the player runs on them, like in the picture below. (the shapes are parsed from Tiled) ...
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2answers
273 views

Box2d: Destroy body or setActive to false?

What is better practice when a body goes out of screen, to destroy the body or just setActive(false)? I guess in terms of memory it is better to destroy it and free the memory, but is destroying ...
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Box2D - Proper way to simulate player's body and feet

I'm new to LibGDX and Box2D, and I'm trying to create my player's body but got some issues. I've created the ground as a ChainShape, and my player as a Rectangle. I want to attach a fixture for its ...
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0answers
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Best practice for frequent sending webSocket/Socketio/webRCT data [duplicate]

I already done game template for classic platformer. I use matter.js for physics and my own override draw functions. Everything works fine. Next stage is to make it multiplayer. I interest is it good ...
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1answer
38 views

LIBGDX - Artifacts when scaling background image

I've got a problem with libgdx. First off, im working with libgdx and box2d on a little physics game. Im using the aproach mentioned in this answer and thereby setting my camera to some smallish ...
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0answers
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Is it better to combine or leave alone 2D polygons

I'm making a modular system for a 2D spaceship arcade like game, the user builds their own ship with equilateral triangles to make more complex shapes. When the ships are small it's no problem, but as ...
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1answer
178 views

PyBox2D car moves uncontrollably

I am trying to program TopDown Car using python and Box2D (similar to this tutorial: http://www.iforce2d.net/b2dtut/top-down-car ) The steering is so far limited to thres states of wheel rotation, ...
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1answer
56 views

Unexpected output from the merging of a quadtree, when that data is converted to Box2D fixtures

I've been staring at this code trying to troubleshoot this for the past 3 days, but I seem to have gone Code Blind. I KNOW the issue is stupidly simple, but I just can't crack the problem. I'm using ...
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1answer
1k views

LibGDX Box2DLights shadow offset problem on bodies

Hello I just started to use LibGDX, and it's awesome. I looked at the Box2DLights library, and started to learn how the lighting work here. I got something up: (source: gyazo.com) As you can see, ...
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1answer
214 views

How do I set the gravity of a plane world

As you can see in the image, the character is set to move on a ground plane, however that causes an issue with Box2d's gravitational pull. The player can go sideways, upwards and downwards on the ...
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1answer
362 views

Box2D physics are different on server and client

I'm using C# Box2D library for my server and client, they have similar world.step(), iterations and update function. At the same time they have different physics' results, difference is not fixed, it ...
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0answers
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How to differentiate between colliding objects in Box2D?

I need to differentiate between different points of contact in my racing game. I currently have staticSensors which determine if the car is on the track or not, but I have created a second sensor to ...
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3answers
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How can I convert a tilemap to a Box2D world?

I want to use Box2D physics and lighting with a .tmx map. How can I "convert" a tilemap to Box2D world? My basic idea is to go through the tiles on the map and ...
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4answers
9k views

Box2D Check If Point Intersects a Body

Is there a way to check if a point is intersecting a body? For example, lets say there's a body in the world at a position of (100,100). Is there a way to check if a point at (100,100) intersects ...
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1answer
445 views

Simulate wind affecting a boat using a 2D physics engine like Box2D or SpriteKit?

I'm looking for a way to simulate the forces created by wind and how it affects a boat. In a nutshell: if wind hits a boat (sailing yacht), the bow is aligning with the wind and if the wind is strong ...
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1answer
54 views

Rotate object around a dynamic object

I'm trying to rotate an object (shield) around another object (player) like this question. My use-case is this: I have players moving around a field. Their respective shield is orbiting in a constant ...
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2answers
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What is inertia in a physics engine?

Inertia seems to be useful in a physics engine, so useful that even in Box2DLite, a demo of Box2D it hasn't been omitted. See this Body class from Box2DLite: ...
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1answer
635 views

How to set a box2d body to follow a strict path

I'm making an infinite runner type game and I want one of my enemies (when it's created) to swoop down in a sort of U motion where it'll hit the player if they don't react quick enough once the enemy (...
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2answers
244 views

How do I implement efficient collision avoidance in 100 enemies

I am developing a libgdx game. It is a top down shooter and I am trying to make a good AI. I have tried to implement A* from the AI library from libgdx and it works fine but when i have a lot of ...
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1answer
318 views

LibGDX Box2dlights - Body Shadow Problem

While playing around with the box2dlights with libGDX, I have managed to get it all up and running, but have a problem with the shadow rendering. This is what I currently have atm: With the lighting ...
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1answer
221 views

What is the physics behind a 2D gravity tunnel?

In Portal 2, there is a concept of an "excursion funnel", a beam of light that moves physical objects in a certain direction. Here is a link to a demonstration. I added a simple implementation that ...
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2answers
615 views

Top-down conveyor belt with Box2D

I'm trying to code a conveyor belt for a project made with LibGDX and Box2D and I would like to make it like this one from Bomberman Land Touch. As you can see, the entities standing on it should be ...
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1answer
544 views

How to implement a camera for a TiledMap with SDL2 and Box2d?

I m writing a game engine using mainly SDL2 and box2D, I implemented TiledMap class that loads a tmx map and everything is fine it even support animation and objects that later will generate Box2D ...
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1answer
52 views

How to make a motorcycle running on a vertical circular track(loop-da-loop) without falling down due to gravity?

I am currently developing a game, motorcycle type game. Of course, my map is not just made up of simple line or curve. For example: a vertical circular track in the map. i've seen most 2D motorcycle ...
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3answers
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Box2D in 3D space

I am trying to combine a perspective camera with a box2D world using libgdx and I am having some problems getting the two to synch up. I want to do this so I can use 3D models but keep the game in a ...
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1answer
244 views

Box2d Javascript Disable Contact Between 2 Objects

I want two objects, when collided, to not effect each other in velocity or force. I have looked up guides and they say to change the PreSolve so that b2Contact.SetEnabled is false... which in code is ...
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1answer
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How can i collide two bodies without filtering(collision filtering)?

I have two bodies with fixtures. One is platform or ground and other is the player itself.I want to collide the player to the platform without bit filtering.How can i do that?I can see the rectangular ...
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2answers
812 views

Libgdx/Box2D PolygonShape has no position… well, what now?

As my prototype works perfectly fine I want to advance to more fun areas of the project and add a more complex player-character body. So for Box2D I figured I'd need multiple fixtures, like one for ...
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1answer
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libGDX, box2d, Ashley ECS - Collision Detection using Box2d does not work when using components with Ashley ECS

I've just recently learned of Ashley ECS while searching up tutorials on the libGDX wiki and I've been replacing many aspects of my code with the Ashley ECS components which has made life a lot easier,...
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1answer
306 views

Problems managing collision filtering

I have my character fixture and body(is a tank), so when I press the screen it throws a rocket(which also has a body and a fixture) that the player can controlll touching the screen. My game also has ...
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1answer
205 views

Does destroying body also destroys the sprite?

Suppose a sprite is attached to a box2d body. And world.destroyBody(b); is getting called then the sprite also get destroyed or it stays there in memory. In my ...
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1answer
739 views

Do I need to roll my own polygon segmentation algorithm to automate Box2d body creation from a tile map?

Before re-inventing the wheel I figured I'd ask: I'm working on a tile-based 2d-maze level generator for cocos2d + box2d. The idea is: I'm using one of the well-known graph traversal algorithms to ...
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1answer
1k views

Box2D + Love2D (Lua) - Assertion fail with polygon meshes

When I try to create a triangle collider for my game it sometimes leads to an assertion fail. I use the physics engine that comes with love2d (Box2D). That's the error message that appears when the ...
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1answer
2k views

Create Box2D and engine polygon Box2D body without sprite

I have created my body using following code: (please read full description) ...

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