# Tagged Questions

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

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### 2D soft-body physics engines?

Hi so i've recently learned the SFML graphics library and would like to use or make a non-rigid body 2D physics system to use with it. I have three questions: The definition of rigid body in Box2d is ...
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### Movement prediction for non-shooters

I'm working on an isometric 2D game with moderate-scale multiplayer, approximately 20-30 players connected at once to a persistent server. I've had some difficulty getting a good movement prediction ...
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### Channelling an explosion along a narrow passage

I am simulating explosions in a 2D maze game. If an explosion occurs in an open area, it covers a circular region (this is the easy bit.) However if an explosion occurs in a narrow passage (i.e ...
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### Physic of an arrow in flight

What are the formulas which represent the horizontal and vertical displacement of an arrow in flight (as well as it angle)? I would like to make sure that I take into consideration the arrow's fluid ...
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### 3D Ball Physics Theory: collision response on ground and against walls?

I'm really struggling to get a strong grasp on how I should be handling collision response in a game engine I'm building around a 3D ball physics concept. Think Monkey Ball as an example of the type ...
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### Problem with impulses in my physics engine

I'm currently developing a small 3D impulse-based physic engine for a CS project. It uses GJK for collision detection and is kind of stable at the moment. Nevertheless, I'm not satisfied with my ...
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### Tried and true basic movement physics (jumping, not walking through stuff)?

If I sat down long enough, I'm sure I could make this happen, but I don't want to reinvent the wheel if I don't have to, especially if XNA has patterns in place for doing this. For now, I'm working ...
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### How are physics or graphics components typically built in a component-oriented system?

I have spent the last 48 hours reading up on Object Component systems, and feel I am ready enough to start implementing it. I got the base Object and Component classes created, but now that I need to ...
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### Bringing a Box2D, Physics Enabled game Online?

Lets say, to simplify the problem of online games a bit, my goal would be to run a near identical simulation on multiple computers in sync. Would sending commands be a good idea? Now if only sending ...
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### How do I detect the direction of 2D rectangular object collisions?

After this question, I need some more help. How can I find out which side of a rectangle a collision came from and react accordingly? The blue arrows are the paths that some circular objects ...
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### Angle of Reflection

I have this "Breakeout style" game. I have a cannon at the center, blocks around the cannon and pads around the blocks. This is how the game looks like: I've managed to get the collision per ...
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### Determining player.isFalling() through change of y?

I'm currently using Box2D and my character is a bunch of fixtures in Box2D. I was wondering if, to determine if a player is falling, detecting a change in Y position would be appropriate? Are there ...
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### What maths should I learn for game programming, and what aspect of programming does it relate to? [duplicate]

Possible Duplicate: What math should all game programmers know? Obviously a good knowledge of maths is essential for good programming, my maths isn’t the best ( I didn’t pay attention in ...
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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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### 2D game physics, doing it right

I have a ball that you can make jump, I have a sneaking suspicion I'm doing this wrong. It works now, to the extend that gravity pulls the object down toward the ground, but I'm having trouble ...
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### Simple physics for modelling ship/submarine movement

for a first iteration of my sim, I need a very basic physics model for ship/submarine movement. I'd guess it might be a good approach to use vectors here (ship heading but also considering sea states ...
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### Recreating retro/NES style physics with intentional imprecision

Background: I'm having a problem getting the jump curve correct for a retro platformer remake project of mine. The original game is for the NES, and the player's velocity is stored in two separate ...
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### ways to make a physics engine

Hey so i've been looking into real time physics engines, which led me to the crazyLaggoa multiphysics engine by thiaga costa, and brought up the question of: What are some possible ways, ideas that ...
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### Collisions between players at spawnpoints

I am working on a FPS/MMORPG and ran into a problem at spawnpoints, when I enabled collision detection between players. Neither player would be able to move if both spawned at the same time, because ...
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### Why is my velocity decaying?

Programming in Java. Tinkering around with physics. My entities all have position and velocity. In the main loop, all I'm doing is applying gravity and bouncing off the edges, like so: // add ...
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### Are game programmers aware of all the physics derivatives?

I am trying to study XNA for game programming. XNA has many methods that can simplify developer's life, such as reflecting the vector when it hits a solid plane. I know these are good and developers ...
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### How can I easily implement swinging in a platformer game?

I'm developing a game in which player can use ropes to swing (just like what Spiderman or Bionic Commando did) and I'm having problem implementing this behavior. Can anyone help me how to do this, I ...
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### Is there a 2d physics engine that can model fluids and gases? [closed]

At this point the platform and programming language don't matter I would just like to know if something out there exists for this. Any help is appreciated.
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### Collision Detection/Response in Vector-based levels

I have a 2D side scroller whose levels are stored as vectors (that is, a bunch of lines) which looks like this: How would I detect that I'm colliding with one of these lines, and react accordingly (...
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### Should I use animated objects or use the physics engine on iOS scenes with lots of rigidbodies?

I have a scene with lots of houses and other objects. These objects will be bombarded from the sky. How to handle these kind of settings having in mind that you want the physics to be as realistic as ...
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### Converting 2D Physics to 3D

I'm new to game physics and I am trying to adapt a simple 2D ball simulation for a 3D simulation with the Java3D library. I have this problem: Two things: 1) I noted down the values generated by the ...
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### Correctly Implementing a “Double Jump”

I'm working on a 2D iPhone game using Corona (Trial version, so I can't use their forums). The game involves the character falling through the sky, and I'm trying to implement a "double jump" for the ...
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### How to balance a ball on a rotating plane?

I'm doing some research and I really don't want a physics engine when a simple mechanism will do. I have a ball that will be balanced on a plane. The ball will always be "stuck" to the plane and ...
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### What is your Unity 3D physics engine budget for iOS games? [closed]

I'm testing Unity for a game that I'm building, and I've touched its limit. My test scenario: a wanna-be house with 200 elements (cubes rescaled) no textures, box colliders and rigid bodies for each "...
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### How do I rotate a segment + normal so that the normal is (0,-1) and the segment is now axis aligned

I have an arbitrary line segment, which may or may not be axis aligned along with its normal eg: Segment(Coord(-1,-1), Coord(1,1), Coord(-1, 1).normalize) which represents a line segment with a 45 ...
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### in Unity3d, how to automatically create fixed joints in a wall of cubes?

I want to create a wall: width 6 cubes height 7 cubes therefore I have 22 cubes on the margins and 20 cubes inside. For each of the margins cubes(except the corners) I have to set 3 fixed joints, ...
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### Controls for physics-enabled game object

I'm trying to put together 2D game on Flash ActionScript. Game objects positions are updated by physics library and I'm trying to control them applying forces and updating these forces every frame. ...
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### Havok physics with a wide range of object scales

So typically Havok works best with normal human sized objects with a gravity of 9.8m/s^2 and dealing with everything in meters. In my Game though there will be a large variety of scales from ...
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### Web workers for HTML5 game physics simulation?

A bit related to this question. The idea is to guarantee the same physics behavior as much as possible. Would it be possible to run fixed time step physics on a web worker? The UI would update ...
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### Why do objects interpenetrate in this simple collision solver?

The code below is from a Microsoft XNA sample here. This is quite a simple rigid body simulation that ignores many physical effects (such as angular momentum), but it does try to push objects (spheres)...
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### Physics engine recommendation which can simulate pool game correctly? [closed]

I'm making a pool-game like game. This game requires correct (or very accurate) reflective bounces. I tried Box2D and Bullet Physics, but they both have this problem. If there is a wall on top of ...
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### How can I make bodies that do not stick to the wall in Bullet Physics? [duplicate]

Possible Duplicate: Physics engine recommendation which can simulate pool game correctly? I made a Billiards scene with Bullet Physics, but I've got a problem. When the ball is slowing down ...
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### Can I change shape of a rigid body after it created in Bullet3D?

I'm beginning Bullet3D. Can I change collision shape of a rigid body after it created? A rigid body accepts a collision shape when it's creating, but it's hard to find options changes the collision ...
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### Gravity strength in first person games

In our game, we set the acceleration due to gravity to the appropriate value of 9.8 m/s^2. Although physically correct, it feels more like moving around on the moon.. It feels about right at a value ...
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### Splitting an object into two

I'm using Farseer physics engine. I have a simple rectangle body and would like it to split into two pieces given a starting coordinate (where the bullet enters the object) and ending coordinate (...
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### 2d Collision detecton axis aligned boxes

I have recently run into some trouble with my collision detection. My game is composed of a map made out of axis aligned squares. The player has an x and y velocity, and I want to know how I can find ...
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### Mouse joint isn't restricting the ball from going to the other part of the screen

I'm developing a application in cocos2d using the Box2D framework, but unfortunately I am having issues. I'm not able to restrict the orange ball in the half screen area, taking the image below as ...
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### How to apply numerical integration on a graph layout

I've done some basic 1 D integration, but i can't wrap my head around things and apply it to my graph layout. So, consider the picture below: if i drag the red node to the right, i'm forcing his ...
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### Basic Box2D collision detection

I don't understand how to listen for collisions in Cocos2D/Box2D. Say I have two dynamic circle bodies. One is very small and the other is relatively large. When the small circle collides w/ the ...
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### Finding the point of collision

I'm writing a 2D rigid body simulator. The objects being simulated are convex polygons. My question involves how to decide on the "point" of collision, so that when I apply a response force, I can ...
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### 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 (...
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### Animated examples of different interpolations formulas: any link? [closed]

I remember having spotted a link to a huge page with different equations to non linear interpolation curves, for example if you want to stop a car smoothly, etc. Those can sometime be useful to ...
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### Physics for a 2.5D platformer with a plane that curves

I'm creating a 2.5D platformer in XNA which uses 3D models that are constrained to travelling along a 2D plane (just like Trine). To make things tricker, however, I want the 2D plane itself to be ...
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### Adding air drag to a golf ball trajectory equation

I'm developing a 2D golf game in VB.NET 2005, but I am stuck on how to implement air or wind drag that should affect the ball. Already I have these equations for projectile: Vo ...
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### Kepler orbit : get position on the orbit over time

I'm developing a space-simulation related game, and I am having some trouble implementing the movement of binary stars, like this: The two stars orbit their centroid, and their trajectories are ...