# 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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### Are collision detection always O(n^2)?

Are physics engine able to decrease that complexity, for example by grouping objects who are near each other and check for collisions inside this group instead of against all objects ? (for example, ...
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### How can I make a character walk on uneven walls in a 2D platformer?

I want to have a playable character who can "walk" on an organic surface at any angle, including sideways and upside-down. By "organic" levels with slanted and curved features instead of straight ...
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### 2D Spatial partitioning alternatives to spatial hashes and quadtrees

I've been trying to implement a spatial partitioning algorithm in my game, but both spatial hashes and quadtrees aren't what I'm looking for. My level size is not supposed to have a limit (only Int32 ...
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### How do I prevent raycast car wheels sliding sideways?

I've been writing a non-realistic car physics engine as a learning exercise, using this article as a reference. I have a car that correctly collides with a terrain and applies the correct suspension ...
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### How can I simulate shattering glass?

I need to make a simulation with stone thrown through a glass window. How can I accomplish that? I mean, I was thinking about making a 3D model of a stone and glass in 3D Studio Max 2012, shatter the ...
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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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### 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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### How do I make a vehicle move to a point and stop without overshooting or oscillating?

Ok so consider we have a vehicle like the one I described in my answer to this question, with a 2D position, velocity, angular velocity, and drag/friction. It can accelerate and break by a variable ...
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### Calculation of Inertia Tensors

Bit of a complex and lengthy question that, I'll admit, I don't quite understand very well yet so I will try and explain as best as I can. Short Version: Is there a general c++/physx formula out ...
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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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### 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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### Can I jump from A to B?

I'm making some rudimentary AI for my side-scroller and I need to know whether an AI unit can reach point B from point A simply by taking a jump. Flight trajectory of my characters is a bit unusal as ...
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### Multiplayer platformer - Are server corrections normally required with a single client on the server?

I am currently working on a rather simple multiplayer platformer. I read quite a bit of articles on the techniques used to hide latency, but I still fail to get my head around certain of the concepts. ...
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### Drone targeting

Imagine a "drone" and a target point on a 2d plane. There are eight parameters: P = my position Q = target position V = my velocity I = my moment of inertia w = my angular velocity s = my angular ...
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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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### How to implement 2d explosions that will cause damage taking into account covers and distance?

How can I implement a 2D explosion in a way that it will cause less damage to characters that hide behind crates or other cover? Ideally damage will depend on the strength of the cover (e.g. metal ...
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### Physics simulation methods for large delta times?

What physics simulation methods are most suitable for really big delta time (hours to weeks)? In addition, would I face any problems combining different methods for big and small delta times?
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### How do I fix objects “popping” or jittering in physics engine?

I've got a simple physics engine that solves collisions by simply correcting the position of overlapping bodies (just circles for now) directly, as opposed to just changing the velocity or applying an ...
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### Who know how to implement the 2D bone animation showed in the game?

I wonder how do they implement the bone animation in the flash game http://www.foddy.net/athletics.swf Do you know any study materials which I can start to learn 2D bone system from? I just ...
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### How to simulate feather fall in box2d?

I am working with AndEngine with Box2d extension, but general answer or a concept idea will be appreciated too. I have feather-like objects in a 2D side view world that I want to be part of the ...
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### What are the common character animation techniques used in tile based hack&slash games?

I wonder what kind of animation techniques are used for creature and character animation in modern hack&slash type tile based games? Keyframing for different actions may be one option. Skeletal ...
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### multiplayer networking with physics

I'm curious how multiplayer networking with physics is implemented in racing games. We have a physical world with multiple fast-moving vehicles controlled by different people. Let's say that vehicles ...
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### Finding the contact point with SAT

The Separating Axis Theorem (SAT) makes it simple to determine the Minimum Translation Vector, i.e., the shortest vector that can separate two colliding objects. However, what I need is the vector ...
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### Simulating an object floating on water

I'm working on a top down fishing game. I want to implement some physics and collision detection regarding the boat moving around the lake. I would like for be able to implement thrust from either the ...
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### Realistic slow-falling snow algorithm?

Is there a good algorithm that simulates falling snow? I'm particularly interested in snow that falls slowly, so it doesn't quite fall in a straight line but deviates a bit. Maybe even including ...
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### Tiling Physics using Farseer

I'm having a problem with the Farseer Physics Engine, where in a tiled environment, my object will at times interact with corners of others objects, even if they align perfectly. I've read about ...
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### Changing orientation by applying torques

Suppose you've got an object floating freely in space. You have a vector you want this object to point towards, and a vector representing the direction it's currently facing. From these two, you can ...
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I have a simple top down bike game that I'm trying to add steering to. I would like to know how I use the heading of the front wheel to determine the heading and velocity of the bike. void Update () ...
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### Physics engine that can handle multiple attractors?

I'm putting together a game that will be played mostly with three dimensional gravity. By that I mean multiple planets/stars/moons behaving realistically, and path plotting and path prediction in the ...
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### Make fast thing look slow (Box2D)

I'm working on a game that you control a trebuchet to throw balls to the opponent. It's like a game called 'Medieval Siege'. When the trebuchet is swinging its arm, player need to seize the best ...
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### Connecting physics simulations with different coordinate-systems

I want objects to move between two physics simulations through a "window" and collide with those from both simulations in case they intersect the window plane. The coordinate systems of the ...
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### 2D Physics: storing previous position vs storing velocity

I saw a number of 2d game tutorials and books where previous position of an object was stored in state instead of velocity vector. Velocity is then calculated each frame as a difference between ...
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### What would be a good filter to create 'magnetic deformers' from a depth map?

In my project, I am creating a system for deforming a highly detailed mesh (clothing) so that it 'fits' a convex mesh. To do this I use depth maps of the item and the 'hull' to determine at what point ...
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### Ragdoll on alive creatures: has somebody already implemented it?

I find that a dead creature falling realistically is boring. I wonder, has any game implemented an animation system where the model moves depending of the muscle forces and the velocity of the limbs, ...
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### Determine Resulting Angle of Wall Collision

So I have an object moving in a direction towards a fixed horizontal or vertical wall. How do I compute the angle that the object should bounce off at? The object can approach the wall at an arbitrary ...
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### Physics library internals

I've seen box2d and bullet ports into javascript, but neither of them attracted me particularly, except by source code. It all seemed, after all, quite simple once I looked inside them. But what are ...
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### Making a Box2D ball bounce to constant height

I want to create a game like Doodle Jump. I'm using libgdx and Box2d. I needadvice on how to make my ball bounce constantly and with the same height. I've tried setting the ball's body restitution ...
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### OpenGL vs physics?

I am very new to game programming and I am in my first project. I have come to a point that I need expert advice: Now for the game physics to be able to work on objects, it needs to know each object'...
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### Typical Maximum steering angle of a real car

I'm building a car sim in Unity3D. I'm trying to set the properties of the car to be as realistic as possible. I can't seem to get a straight answer on Google so I thought of asking here. What is the ...
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### How to handle physics of moving platforms in a platformer?

So after a few hours of searching on the internet, I have yet to find a pleasing answer on how to handle moving platforms in a 2d platform game. So I decided to make a simple prototype where you ...
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### How can I factor momentum into my space sim?

I am trying my hand at creating a simple 2d physics engine right now, and I'm running into some problems figuring out how to incorporate momentum into movement of a spaceship. If I am moving in a ...
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### Projected trajectory of a vehicle?

In the game I am developing, I have to calculate if my vehicle (1) which in the example is travelling north with a speed V, can reach its target (2). The example depict the problem from atop: There ...
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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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### Elliptical orbit modeling

I'm playing with orbits in a simple 2-d game where a ship flies around in space and is attracted to massive things. The ship's velocity is stored in a vector and acceleration is applied to it every ...
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### Determing an object's position along a curve over time

I have some objects in my game which are "thrown". At the moment I am trying to implement this by having these objects follow a parabolic curve. I know the start point, the end point, the vertex and ...
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### Calculating Linear force required to hit a specific vertex on a parabola

The idea is a user presses somewhere on the screen and the program will fire an object in a parabola shape from a defined start position that has it's vertex where the user touched the screen. I have ...
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### Get collision details from Rectangle.Intersects()

I have a Breakout game in which, at some point, I detect the collision between the ball and the paddle with something like this: // Ball class rectangle.Intersects(paddle.Rectangle); Is there any ...
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### Differential programming for a vehicle

I am to a point on my vehicle where, when im going fast and turning, the vehicle acts weird because the inside tires are moving faster than the outside tires. So i need to figure out how to program in ...