# 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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### Which techniques to study? [closed]

Just to give you some background info, I'm studying a programming major at a tertiary level and am in my third year, so I'm not a newbie off the street. However, I am still quite new to game ...
2k views

### How can I convert a 2D bitmap (Used for terrain) to a 2D polygon mesh for collision?

So I'm making an artillery type game, sort of similar to Worms with all the usual stuff like destructible terrain etc... and while I could use per-pixel collision that doesn't give me collision ...
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### How to take into consideration the effect of initial rotation of a ball hitting & reflecting off a surface

Hey all, I am trying to take into consideration the effect of inertia of the initial rotation of a ball, hitting a surface, into the exit velocity vector of the ball. My current theory is this: ...
287 views

### How do I simulate a trampoline?

I'm quite new to game development. I was pretty impressed with the elastic effect I saw in this flash game when the ball hits the trampolines and I'm wondering how to recreate it. I've done some ...
209 views

### How to manage sleep/awake state of physics body

I have a loop, which updates all the physics, inside the loop I'm updating the position of the objects, first thing is the gravity, which pulls all the objects to the bottom. Now my question is, how ...
467 views

### 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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### Box2D stable range and position

Box2D marks stable range of object size is 0.1M ~ 10M. This specifies object size range. How about space size? If I make an 1M object at (1000.0f,1000.0f) position? Is it can be stable? Or should I ...
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### Problem with box2d at beggining

I have problem with simple box2d physics: I have two bodies : 1 - static box , 2 - dynamic box. I only want to this dynamic box fall on this static, and lay. But now it looks like that at end , ...
2k views

### 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 ...
1k views

### 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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### Why is Euler integration sometimes preferred over RK4 even if RK4 is more accurate? [closed]

Some high quality engines such as Box2d uses the Simplistic Euler integrator instead for RK4 when Eumplectic Euler commits a global error of the order of Δt whereas, RK4 has Δtˆ4 error? RK4 is not ...
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### How to handle jumping up a slope in a runner game?

In an 2D endless runner, what should happen when the player is running "too fast" up a slope and jumps? For example, in a "normal" case: .O. . __..O_____ . / . / O/ _/ If he is moving ...
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### 2D game with 3D collision?

How do they do this bounce? Looks awfully complicated in 2D.
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### Fluid Particle Grid

So recently I have been looking at some fluid simulation techniques, specifically Smoothed Particle Hydrodynamics. One of the key components is a grid to avoid O(n^2) searches. I have been having some ...
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### 2D Smooth Turning in a Tile-Based Game

I am working on a 2D top-view grid-based game. A ball that rolls on the grid made up of different tiles. The tiles interact with the ball in a variety of ways. I am having difficulty cleanly ...
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### Creating a frozen bubble clone [closed]

This photo illustrates the environment: http://i.imgur.com/V4wbp.png I'll shoot the cannon, it'll bounce off the wall and it's SUPPOSED to stick to the bubble. It does at pretty much every other ...
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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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### Adding 'swerve' to a direction

I'm not much of a maths expert, so this is probably quite straight forward. I was playing a soccer flash game where you take free kicks. You provide Power, Swerve and Direction. I'm reading up on ...
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### Sensor based vs. AABB based collision

I'm trying to write a simple collision system, which will probably be primarily used for 2D platformers, and I've been planning out an AABB system for a few weeks now, which will work seamlessly with ...
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### Physics System ignores collision in some rare cases

I've been developing a simple physics engine for my game. since the game physics is very simple I've decided to increase accuracy a little bit. Instead of formal integration methods like fourier or ...
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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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### A Star pathfinding algorithm, multiple node set optimization

I'm trying to determine if this is an optimization I should pursue or if this is way to complicated to be worth my time. I've successfully implemented the A Star Algorithm for my video game. I used ...
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### How to implement throw curve with virtual height in a 2D side-view game

I am working on a 2d side-view soccer game that looks like this image: But now I stuck on how to implement parabola pass ball. I have found many questions corresponding to my problem: Calculating ...
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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 ...
1k views

### When and how should I apply forces in a Cocos2D + Box2D game?

I have some small circles just rolling across the bottom of the screen in my Cocos2D/Box2D iOS app. The bodies are dynamic... so I make them roll by applying a horizontal force to the center of mass ...
310 views

### Calculating impulse with multiple collision points

In my amateur 2D rigid body physics engine for a game I react on collisions between two bodies with an impulse j (formula 11) as explained here. To calculate this impulse I need one contact point P ...
1k views

### Movement & Physics in an entity-component system

I'm currently playing around with entity-components systems and got started on the movement/collision/physics parts and would like to have some pointers! It's a basic 2D sidescrolling game, with the ...
1k views

### Moving a body in a specific direction using XNA with Farseer Physics

I have a custom polygon attached to a body, which looks like this: What I am trying to accomplish is getting the body to move according to wherever the tip of the body is. So far this is what I've ...
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### Collisions between moving ball and polygons

I know this is a very typical problem and that there area a lot of similar questions, but I have been looking for a while and I have not found anything that fits what I want. I am developing a 2D ...
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### 2D Ragdoll - should it collide with itself?

I'm working on a ragdoll fighting game as a hobby project, but I have one dilemma. I am not sure if my ragdoll should collide with itself or not, i.e. if ragdoll's body parts should collide. 2D ...
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### Good ways to edit arbitrary collision shapes for 2D physics engine?

Assume you have several 1024x1024 textures which contain an arbitrarily shaped and relatively complex cave system whose walls need to have collision polygons defined. The polygons need to be convex to ...
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### Calculate point of circle–circle collision between frames

I need to find the exact XY coordinate where a circle collides with another circle calculated between frames. This means that I take the coordinate of the moving circle on the previous frame and take ...
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### Realistic 2D Planetary Physics Engine?

I'm doing a spaceflight simulator in C++ (using Allegro 5), and I realised that I could just use a physics engine instead of writing my own physics. So that's what I'm doing. Since this is going to ...
1k views

### Non-physics character movement in a Box2d Environment

I am in the process of creating a physics platformer. However, I want the player movement to feel very old-school(as in: non-physics like), which means that the character: Should always move equally ...
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### 2D Motocross physics

I'm looking into making a 2D motocross bike game with plausible physics. It should look like this: For a first try, I've created only the player (a motocross driver) and the map (consisting of ...
11k views

### 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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### Moving object through nodes in Quadtree

I'm working on my own quadtree for use in games for physics (collision detection to be exact) but am unable to move an object from one node to another node. What I'm doing is if some object is to be ...
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### How to implement server side physics?

I am working on 2-player 2d sidescroller. How should I implement the physics on the server? Use one world for every game or use a big world in which I add every 2 player that start a game? I have ...
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### What to do after detecting OBB-OBB intersection

I'm using this code to detect intersections between two OBBs. The problem is that i don't know what to do after detecting it. I tried using a simple algorithm: if (collision detected) { ...
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### Nape physics - Moving a body

Hey I'm currently getting started with physics engines and I set up a body (box shaped) which represents my character. Question: Which methods can I use to move a Nape.Body aka my char? I tried so ...
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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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### How can I smoothly rotate a joint to an angle? [duplicate]

I would like to set the speed of my Box2D revolute joint on every update such that it rotates to a desired angle and stops. It should ramp down as its angle approaches the desired angle. My first ...
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### How to Make Objects Fall Faster in a Physics Simulation

I used the collision physics (i.e. Box2d, Physics Body Editor) and implemented onto the java code. I'm trying to make the fall speed higher according to the examples: It falls slower if light object ...
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### Simple 2D hair simulation/manipulation

I would like to simulate very simple hair in a 2D environment, and will need to be able to "brush" the hair. What I want to do: A 2D character is facing squarely towards the player. The player can ...
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### How should I implement basic spaceship physics?

I am new to 2D game development. I've made several games, but they've made almost no use of physics. Now I want to try making a game that uses some basic physics to look more realistic. The game ...
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### How to obtain “gravity” and “initial impulse” given “desired time to reach max height” and “desired max height”?

I'm developing a 2d fighting game, using time steps based on frames ie, each call to Update() of the game represents a frame so, no variable time at all. My jump physics code doesn't need to consider ...
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### Arc'd jumping method?

Okay, so I'm making a platformer, and I wanna know how I can make a arc'd jump easily. Like what Mario does in super Mario Bros 1. Any ideas on a simple way to accomplish this?
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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?