# Tagged Questions

Relating to the motion of objects through space (in 2 dimensions (x,y)) and time. Including concepts such as acceleration (thrust and gravity), mass, collision response, friction and more.

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### Box2D platformer movement. Are joints a good idea?

So i smashed my brains trying to make my character move. As i wanted later in the game to add explosions and bullets it wasn't a good idea to mess with the velocity and the forces/impulses didn't work ...
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### JBox2D applyLinearImpulse doesn't work

So i have this line of code: if(input.isKeyDown(Input.KEY_W)&&canJump()) { body.applyLinearImpulse(new Vec2(0, 30), cam.screenToWorld(body.getPosition())); ...
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### Debugging Minimum Translation Vector [closed]

I implemented the minimum translation vector from codezealot's tutorial on SAT (Separating Axis Theorem) but I'm having an issue I can't quite figure out. Here's the example I have: As you can see ...
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### Physics in carrom like game using cocos2d + Box2D

I am working on carrom like game using cocos2d + Box2D. I set world gravity(0,0), want gravity in z-axis. I set following values for coin and striker body: Coin body (circle with radius - ...
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### Car movement in arcade racing game

I am finishing a very basic 2D racing game with top-down perspective. I can't get the appropriate formulas to make the movement of the cars fun and addictive... Do you have tips on how to achieve that ...
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### How to pin a body in case of collision in Box2D or Farseer?

I'm trying to get an understanding for the Box2D/Farseer physics engine by implementing a small air hockey simulation. There, I have the problem that the CPU player attacks the puck, kicks it, but ...
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### Making a multi-pieced rectangular breakable body with Farseer

Using Farseer 3.3.1 I want to create a rectangular BreakableBody with many pieces. Right now here is my code: Vertices polygon = PolygonTools.CreateRectangle( 2.5f , 1.25f ); List<Vertices> ...
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### Farseer Physics collision detection vs intersection detection with sensors

I'm trying to make a game that uses Farseer physics engine as its main collision detection engine. I have a 2d circle body object that has a matching fixture (I used the CreatCircle method. I did not ...
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### Ball Physics for Android Game

I am starting work on a new Android game and I haven't had any experience implementing physics before. I am trying to steer clear of external libraries such as box2d, not just because I think it is ...
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### Making an object swing from one rope to another

I am trying to make a Tarzan like game with Cocos2D and Box2D. I am having issues with the physics - making an object swing from one rope to another. I am not really sure how to do this. Could anyone ...
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### Using Vectors for 2d animation [closed]

I've decided that it's best to start using vectors in my games instead of the xPos += xSpeed and yPos += ySpeed approach. I'm posting some of the code from my basic model class which handles movement ...
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### How to simulate backspin or topspin in a box2d billiard game?

I am designing a simple billiard game with box2d. I think I can easily simulate hitting left or right side of a ball. Since box2d is not 3D, however, I am not sure how to simulate hitting upper or ...
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### How to build a bones animation engine?

I want to develop a flash game. It would draw a stick man, and edit his pose. I think what I need to learn are bones animation and physics engine. Can anyone introduce some good resources to learn ...
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### Player moving up, is he jumping or climbing?

In a 2D physics-based platformer game that has ladders in it, how do you determine whether the player moving up is caused by a jump or him climbing a ladder, such that you know what animation to play? ...
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### When connecting a physics engine to another engine, should you do all your logic in the units used by the physics side or the rendering side

I'm currently intergrating pygame and pyBox2D, and am wondering which side is best to try to keep to in terms of game units of size. Box2D is Meters PyGame is Pixels At the moment I am thinking I ...
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### How to resolve concurrent ramp collisions in 2d platformer?

A bit about the physics engine: Bodies are all rectangles. Bodies are sorted at the beginning of every update loop based on the body-in-motion's horizontal and vertical velocity (to avoid sticky ...
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### Ways to define a curve

I'm trying to give shapes in my physics engine roundness/ curvature. I am aware of various methods for mathematically defining curves; such as bezier-cruves, ellipses, etc. However I am not sure ...
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### Canvas Rotation collision detection on a sprite

I am using this code to detect collisions between two rectangular sprites. intersect: function(other) { return this.x < other.x + other.width && other.x < this.x + this.width ...
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### Is there a good existing starting point for realistic 2d racing car physics?

I'm trying to get a realistic behaving racing car into my 2d top-down game. Making a very simple car that drives around is straight forward but I want a reasonably sophisticated model that models ...
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### 2D physics engine for WP7?

I'm looking for a 2D physics engine for Windows Phone 7. Is there a port of something existing for use?
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### How do I change my gravity and jumping logic to put the character at a specific height at a specific point in time?

I'm making a 2D platformer on Android using libGDX. One thing I've had a problem with recently is gravity and jumping. I found a few tutorials on the internet and was able to come up with this... ...
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### 2d engine/library for android in C#

I'm looking for a good 2d engine or library (that supports physics) for Android. I have a restriction - language should be C#. It's not a requirement to use Mono Droid, but it seems that it is an ...
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### Implementing jumping and heightmaps in 2D RPG/Adventure style games?

I've been putting together, albeit slowly, a traditional style game engine in flash/AS3 along the lines of Alundra/Final Fantasy 3/etc etc.. Everything so far is working smoothly (maps from XML data, ...
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### Continuous Physics Engine's Collision Detection Techniques

I'm working on a purely continuous physics engine, and I need to choose algorithms for broad and narrow phase collision detection. "Purely continuous" means I never do intersection tests, but instead ...
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### Is there a 2D soft-body physics engine for Flash?

I'd like to write a small physics game by using ActionScript, but do not want to write my own physics engine. Does anyone know a ready-to-use 2D soft-body physics engine with a Flash port?
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### Collision filtering techniques

I was wondering what efficient techniques are out there for mapping collision filtering between various bodies, sub-bodies, and so forth. I'm working on a physics engine and I need ways for a user to ...
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### Axis-Aligned Bounding Boxes vs Bounding Ellipse

Why is it that most, if not all collision detection algorithms today require each body to have an AABB for the use in the broad phase only? It seems to me like simply placing a circle at the body's ...
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### How can I make a car follow the terrain in a 2D (side-view) game?

I'd like to create a game where a car drives over a 2D terrain. Which algorithm to use so the car will follow the mountain incline?
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### How do I set up moving platforms in a 2D side scroller to interact with the player properly?

Edit: I changed the way that gravity was applied so that it is applied even when a player is standing on a block, so instead of the game outputting that you are stepping on a tile as true and false ...
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### How do I move a 2D top-down racing camera smoothly and show what's ahead of the player?

I'm trying to make a camera that follows a race car. Right now, I'm smoothing the camera movement out by moving the camera's position a fixed percentage lerp'ed from the camera's position to the car's ...
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### How does one avoid the “staircase effect” in pixel art motion?

I am rendering sprites at exact pixel coordinates to avoid the blurring effect caused by antialiasing (the sprites are pixel-art and would look awful if filtered). However, since the movement of the ...
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### How to use rigid bodies for characters?

First off, I am making a game similar to SSB, which relies heavily on physics, even though it is a sidescroller. I am currently using Unity. In Unity there are "character controllers" which are used ...
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### Ideas for 2D Water Simulation

I am looking for any input on simulating water in 2D, against a rather large (call it) blocked/not blocked array (viewed from the side). I have come up with the following ideas: Cell Automata Do a ...
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### How can I implement revolute (hinge) joints in a 2d physics system?

Further to my previous question on fixed joints, I am now going toe-to-toe with hinge joints in 2D physics. Though the answer to the previous question was excellent, I have come across a few problems ...
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### Best Android gaming engine for Billiards game? [closed]

What is the best engine/way to go with when implementing a 2D billiards game? I am thinking about Emini Physics Engine, which is free for use and stuff, but maybe you can give me some pitfalls about ...
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### Equation to make small number big and big number small (gravity)

I have a sprite that I want to speed up as it gets closer to another object. I really want this to flow well and don't want a series of if statements. All I can think of is to take the distance and ...
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### How to make a 2D Soft-body physics engine?

The definition of rigid body in Box2d is A chunk of matter that is so strong that the distance between any two bits of matter on the chunk is completely constant. And this is exactly what ...
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### Shapes and sprites in SVGs

I understand SGV images are used in 2D games to store shape data for the physics engine of the game. I'm unsure though, should the raster sprite also be stored in the SVG or should it be separate? ...
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### Physics in a 2D oblique perspective game

So, just to clarify, because I'm still fuzzy on the terms for perspectives in older games myself, examples of an oblique perspective can be seen in many older RPGs (Earthbound, Final Fantasy, Secret ...
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### Creating similar effects of Geometry Wars in 2D only

I want to create a game with similar effects to that of "Geometry Wars"... for those who have never played the game, basically, massive amounts of 'bending' and 'warping' effects are done on the ...
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### Android Fling Gesture, Animation And Collision - Resources?

I'm starting work on a 2D Android game where the player will put their finger on a game piece and do a fling gesture to throw the piece across the gameboard. I've gone through some Android ...
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### How to get object to lose less velocity as its speed increases

I'm developing a game in Flash and I need a little help. It can be considered a math problem. My object is flying with speed X and my object can collide with stones. When it collides with a stone, I ...
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### How can I cancel a contact in a b2ContactListener?

To know when contacts happen we can derive from b2ContactListener and implement our own solution which is great. I'm wondering is there anyway we can cancel a contact, that is to say when we hit begin ...
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### Bodies are colliding but refusing to rotate in Box2D

I'm running box2d in C++ and hooking it up to C# via p/invoke. All physics stuff occurs in C++. My problem is that bodes know when they are colliding and do so with great precision. However if I have ...
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### 2D physics library that supports curved surfaces and inverse or boolean shapes?

I've been using box2D for a few months, but I now badly need a physics library which can use boolean shapes (ie; cutting a circle out of a square) and/or curved surfaces. Does anyone have any ...
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### Why are my objects becoming permanently stuck to walls using Box2D?

I setup a simple simulation environment something like billiards. There are four circle balls (dynamic) and four box walls (static). Simulation works... except one thing. Sometimes when a ball rest ...
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### 2D Physics Engine for Platform Games - Riding on a Platform

I have a number of questions relating to using a 2D physics engine in a platform game, but one main one that I'm grappling with at the moment. I managed to somewhat integrate the Physics2D.Net engine ...
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### Need help with collision detection/resolution in a 2D simulation of 'worm-like' creatures

(originally posted this on regular stack overflow, somebody pointed this forum out :-) ) Hi there, I'm implementing a physics engine for the simulation of worm-like creatures. Problem is, is that ...