# 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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### Correct way to use Farseer Physics in XNA

I am using Farseer Physics for my 2D sidescroller game and I'm not sure how to proceed with it. I currently have a Sprite class (handles nothing but graphics), a GameObject class (contains specific ...
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### Rotating sprite around another sprite

I am building a pool game, and I want to make the cue rotate around the white ball. Here is the live code: http://199.26.84.223/nocol.html Here is the code for the white ball: balls = game.add....
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### Orbits: Combine the Pros of RK4, Symplectic Euler, and Verlet Velocity Integrator

Recently, I've implemented and compared a number of basic integrators for my physics engine. The 3 that gave me the best results are RK4, Symplectic Euler, and Verlet Velocity, but I think I need ...
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### Circle Collision Resolution and Angular Momentum

I have a 2D engine working pretty well that involves rectangles and circles. I just reworked parts of the collision detection/response system for better handling of angular speed/momentum. The ...
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### How do I make a slot car game?

I new to game development with Unity and my first project is a slot car racer. For a realistic slot car-like-driving experience, I first build a track with a channel in the track and a pin on the car. ...
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### “Super meatboy”-ish replay

I'm making a platformer built from mini-levels - and I want to create a sort of a replay of all the player tries that the player did for the level. My question is - what is the best way to record the ...
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### 2D Platformer Collision/Physics Problems

I'm making a 2D platformer similar to Terraria, although I'm having some problems with some collision detection code. I'm using the code from the AppHub Platformer sample, but tweaked so it fits with ...
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### Looking for very simple implicit integration example

I am trying to design a robust cloth system. I have no problem at all simulating things like that using forward integration such as euler, midpoint, runge-kutta, verlet, etc. However, I just can't ...
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### Friction in 2D game

I'm developing a 2D platformer, although this question could probably apply to just about any 2D type physics; What is the equation for friction? I have sort of a hacky type of friction set up in my ...
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### The Physics behind 2D Platformer Games? [closed]

Is there any good book or tutorial that explains the physics behind creating a 2D Platformer game? Such as tile rendering, tile map reading, collision detection, camera movement etc.?
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### Easiest Way To Implement “Slow Motion” and variable game speed in XNA?

I have an XNA 4.0 game that I want to be able to switch into slow motion and back again to full speed every now and then. So if you kill an enemy the game switches into slow motion as they explode ...
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### How does this formula for generating water waves work?

I have been trying to implement the wave equation described in this paper ("Water Simulating in Computer Graphics," Kai Li and Liming Wu) in Java. Part of the paper discusses modeling waves as a sum ...
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### Is knowing physics necessary for game development? [closed]

Is knowledge of physics necessary to design quality games? How important is it? Be realistic and explain a few novice examples of how's mandatory. What kind of physics is necessary, non-calculus-...
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### Dealing with collisions across adjacent static bodies

The Problem: I have the following setup: A, B and C are rectangular static bodies in box2d. p is a circular dynamic body in box2d. The movement of 'p' is solely controlled by the current gravity ...
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### Why are we not using integers in game physics?

We can use integer for game physics (or without physics, simply object representation): mass, position and rotation, where the integers represent, for example, the number of milligrams, millimeters or ...
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### Problem representing torque as a quaternion

Euler angles are much more intuitive to me than quaternions for representing 3-dimensional rotations. In fact, I barely understand quaternions at all. I use quaternions for rotation because people ...
232 views

### How do I make a tile passable in one direction only?

I want that my character can jump through some of the tiles, like Mario does in this video: http://www.youtube.com/watch?v=zIPYzbNrNhc In this video, Mario jumps up through orange platforms, but ...
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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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### Physics timestep questions

I've got a projectile working perfectly using the code below: //initialised in loading screen 60 is the FPS - projectilEposition and velocity are Vector3 types gravity = new Vector3(0, -(float)9....
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### 2D Enemy AI reacting to sound

I'm currently working on a 2D top-down survival game and I'm trying to figure out a good method for enemies to detect player sounds. For instance - if the player fires his gun it should play a sound (...
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### How can glass breaking effect from Smash Hit be achieved? [duplicate]

I saw Smash Hit the other day and was amazed by the physics of the game, specially the shattered glass effect: I've read other posts about this subject but I still feel that they don't share enough ...
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### How to circle a target at a constant distance

I have an AI ship that stops approaching when it gets within firing range, and starts strafing around its target. The problem is that it doesn't circle its target very well. The following code ...
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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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### Farseer - Apply Impulse

I'm new to Farseer and have a simple question. The demos I went through didn't seem to demonstrate what I want. I would like to apply an impulse (not force) to an object at a specific position on that ...
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### Multiple Colliders in Collision

I have an object that has a front collider, left collider and right collider. When a collision occurs, I notice that there are situations where the front collider and left collider/right collider has ...
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### How can I implement fixed joints in a 2D physics system?

I'm developing a simple, 2D physics system to complement an entity/component game object framework. So far, I have implemented some basic, tutorial-level physics. An entity that is affected by physics ...
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### Programming Dynamic 3D Water/Waves?

I'm a little bit stuck on how I might go about programming dynamic, interesting water in a game. To qualify that a little bit, I'm interested in creating water with broad, rolling waves that affect ...
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### Determining a sensible gear-like hierarchy for a series of connected objects

I would like a series of objects to behave in similar manner to a series of connected gears. This means that each black object in the diagram below will rotate at a speed based on the ratio of their ...
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### Multiple collisions within a single frame cycle?

So say you want to simulate several objects in two dimensions, just bouncing around in a finite space. Using AABB and sweep tests, it shouldn't be that complicated to calculate single collisions ...
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### Collision detection in 3D space

I've got to write, what can be summed up as, a compelte 3D game from scratch this semester. Up untill now i have only programmed 2D games in my spare time, the transition doesn't seem tough, the game'...
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### Physics or Time-Based Animation In Corona SDK (iOS) Using Box2D

I am part way through creating a Doodle Jump clone for iOS using Corona SDK. I'm currently using the physics engine (box 2D). It's not a straight clone, but I need the basic principles in place to ...
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### Collision response for 2D racing game

The title is fairly self-explanatory. I have a 2D racing game that utilizes per-pixel collision detection (the track is essentially two bitmaps, one for the graphics, one for collision data). The ...
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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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### 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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### Strangeness when simulating a chain

I'm using box2d and I simply hook up 10 points each with a similar length constraint to the adjacent point. When I move 1 point, the others follow just like a rope/chain. Just like one would expect. ...
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### 3D Particle-Geometry collision

I am programming a particle engine for a 3D game written in XNA. I was wondering if somebody could point me in the right direction or perhaps give me some pointers in making the particles collide with ...
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### Finding new position after collision with multiple colliders

What is the most accurate way to find the correct position to where a moving character should be re-positioned as a collision-resolution, after it has collided with multiple colliders? The figure ...
309 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 ...
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### Character Movement in 3D games

I'm either not searching correctly or there is really not a lot of material on Character Movement in 3D games. I'm mostly interested in how people usually implement character movement in games like ...
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### Networked Physics - Interpolation Causes Physics Engine to Explode

A major issue I am encountering right now is that my physics engine (BEPU) and my network interpolation are conflicting with each other. The player is a physics object, and so the physics engine ...
461 views

### Physics-based dynamic audio generation in games

I wonder if it is possible to generate audio dynamically without any (!) audio assets, using pure mathematics/physics and some input values like material properties and spatial distribution of content ...
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### 2D Car Simulation with Throttle Linear Physics

I'm trying to make a simulation game for an automatic cruise control system. The system simulates a car on varying inclinations and throttle speeds. I've coded up to the car physics but these do note ...
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### What is a simple deformer in which vertices deform linearly with control points?

In my project I want to deform a complex mesh, using a simpler 'proxy' mesh. In effect, each vertex of the proxy/collision mesh will be a control point/bone, which should deform the vertices of the ...
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### BEPUphysics collision with generated terrain?

I've got randomly generated terrain which is stored in a indices and vertex buffer. How do I go about using this for collision in BEPU? It seems I can do it with a Mesh but it would be a waste to ...
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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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### 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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### Should the bullet trajectory calculated by server or by client? [duplicate]

In a FPS game like Battlefield or Arma, when playing online, should the bullet trajectory be calculated by the server or by the client?
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### Why isn't this physics code scaling velocities separately?

I'm working my way through this book and I'm trying to work this code out: var squaredVelocity = this.velocity.x*this.velocity.x + this.velocity.z*this.velocity.z; if (...