# 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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### 'Spring' physics

I'm trying to put together a struct or a method of some sort that will allow me to check the relative position between two objects, and if they're too far apart, apply a force that will draw them ...
8k views

### how to ignore physics collision of some objects in box2d

I know this sounds silly but I would like some objects to follow physics while others not to collide each other. I tried to achieve them by setting their position exclusively. But then it will ...
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### Self-righting agents that have fallen over

I need insect-like agents that have fallen/rolled on their back/side to naturally re-orient themselves. The agents are modeled as simple cuboids in the physics engine (Bullet) to approximate an ant-...
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### How to calculate the exit speed of ball bouncing off a solid surface

Hey all, I am working on a simple game to include some rigid body dynamics, involving placing (moving & rotating) some springs to bounce a falling ball into a target area. My problem is correctly ...
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### Do I need path finding to make AI avoid obstacles?

How do you know when a path-finding algorithm is really needed? There are contexts, where you just want to improve AI navigation to avoid an object, like a space -ship that won't crash on a planet ...
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### How to make a fan like behavior

I am making a game in Unity. I have an object e.g. cube. I want to release air from it like fan so that when other cubes come closer, it throws them away. What velocity,force etc I will need to do ...
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### Why do Physics Engines use collision margins?

When using a physics engine in a game (such as Bullet), you usually need to define a collision margin for each object. I'm a beginner to game development, and I don't understand the purpose of a ...
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### How to create rope?

I'd like to re-create this game, but I have no idea how to create the rope, or its influences on the ball. Basically, there is a rope, "attached", at one end, to the mouse pointer, and at the other ...
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### Whats the physics behind the doodle jump game?

I'd like to know how we can achieve the doodle jump type physics using andengine. I mean the character is not colliding with the ground blocks when he moves upwards but will collide when he came ...
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### Which Side Was Hit?

I am working on an Android game and I have two objects A and B (both rectangles) and when they collide I simply want to know which side of B was hit. I have detected the collision fine, but I am ...
3k views

### Calculating the angular direction from velocity

I'm trying to calculate the angular direction of a projectile, knowing it's X and Y velocity I can find the magnitude of its movement, but I'm having a hard time wrapping my mind around getting the ...
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### Ball bouncing infinitely and constantly

Alright, so I've got hold of some simple physics mechanics, and am currently trying to implement bouncing. Based on the first answer of this question, I've developed the following algorithm: ...
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### How to lead a moving target from a moving shooter

I saw this question: Predicting enemy position in order to have an object lead its target. My situation is a little different though. My target moves, and the shooter moves. Also, the shooter's ...
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### Is it possible to have concurrent collision detection where every entity acts at exactly the same time?

There are many algorithms that can be used for collision detection. In many cases we check for an overlap in coordinates of an entity. If we make a triangle a,b and c. We have 2 entities at a and b ...
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### Change in direction should slow down object and accelerate in new heading (2D grid-based)

I'm trying to implement some sort of faux space physics in my 2D game. I have a top down view of my space ship. You can change direction and set a speed up to a maximum which then accelerates the ship ...
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### The physics equation for a perpetual seesaw

I am trying to create a game that involves two or more people jumping on a seesaw and propelling each other in the air. I need help with the physics equations Assume no friction and no air ...
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### 2D car physics and high speed turning

I've been looking at the following page, which has been very helpful: http://www.asawicki.info/Mirror/Car%20Physics%20for%20Games/Car%20Physics%20for%20Games.html but have come into problems with the ...
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### Calculate gears rotation for a realtime simulation

Hi I'm trying to do a game with real time simulations of gears. There is a big Gear with inside a smaller gear. I managed to draw gears with different diameters but equal size teeth, but if i try to ...
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### Making AI jump on a spot effectively

How to calculate, in 3D environment, the closest point, from which an AI character can jump onto a platform? Setup I have an initial velocity V(Vx,Vy,VZ) and a spot where the character stands still ...
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### Show path of a body of where it should go after linear impulse is applied

I am making a game with Andengine and Box2D. I have a dynamic body and I apply linear impulse on the body to move it around when the user have touched the screen. Now I want to show the path where ...
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### How do I change the speed of an object without changing path travelled?

I have a ball which is being thrown from one side of a 2D space to the other. The formula I am using for calculating the ball's position at any one point in time is: x = x0 + vx0*t y = y0 + vy0*t - 0....
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### How does 2D Game Physics work? [duplicate]

Possible Duplicate: How do I build a 2D physics engine? If we take the game Angry Birds that had big success lately I were thinking how do they implement the physics in a game like that? Your ...
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### Physics in my game confused after restructuring the Game loop

I'm on my way with making a game in Java. Now I have some trouble with an interpolation based game loop in my calculations. Before I used that system the calculation of a falling object was like this:...
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### Game physics presentation by Richard Lord, some questions

I been implementing (in XNA) the examples in this physics presentation by Richard Lord where he discusses various integration techniques. Bearing in mind that I am a newcomer to game physics (and ...
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### Automatically generate low detail collision meshes

I lately integrated Bullet Physics into my little game engine, but for now I only use basic shapes as spheres or boxes for collision checks. For more realistic physics I need collision meshes for all ...
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### Physics/Logic behind self-bounce

What would a ball look like when it makes itself bounce. Say, for example that the ball had its own "inner power", was made out of (mostly) rubber, and pulled the top of itself inward and then ...
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### 2D Collision in Canvas - Balls Overlapping When Velocity is High

I am doing a simple experiment in canvas using Javascript in which some balls will be thrown on the screen with some initial velocity and then they will bounce on colliding with each other or with the ...
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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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### Orbital mechanics: orbit as a function of time. Universal variable formulation?

I am trying to model a two dimensional orbit for a two body Kepler problem but have gotten stuck when introducing the time variable. For a satellite with known semi major axis (a), eccentricity (e), ...
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### Tracing a 2d path through multiple gravity fields

For a projectile starting at origin O, an initial velocity V, and several stationary planets P[n], how would I pre-calculate and store the path it would take without actually stepping through each ...
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### 2D Polygon Triangulation

I am creating a game engine using the JBox2D physics engine. It only allows you to create polygon fixtures up to 8 vertices, To create a body with more than 8 vertices, you need to create multiple ...
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### How is 'mass' handled in video games?

Mass is one of the basic scalar quantities, which is required in most rigid body physics calculations. Does every, EVERY, object which moves in a game get mass defined in the code, or is it allotted ...
582 views

### 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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### How to make bird to fly using box2d

I am new to Box2D, I have set gravity to 10. How to make an object fly in space even though the gravity is 10. What are the properties I need to set to make object fly? Is there any different approach?...
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### Soft body, where to start learning?

I want to ask you about some resources to learn simulating soft bodies, do you know some good knowledge sources? I asking because I want to make car crash simulator, I've made something but it didn't ...
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### What causes Box2D revolute joints to separate?

I have created a rag doll using dynamic bodies (rectangles) and simple revolute joints (with lower and upper angles). When my rag doll hits the ground (which is a static body) the bodies seem to ...
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### 2D AABB collision response

I'm making a simple platformer, and I wanted simple collision handling. So I gave all my objects an AABB hitbox and tried to resolve collisions. However, I can't get it to work. My main character has ...
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### How do I set an object's speed to arrive in X seconds?

I want to move an object to a point in the game world, I have the distance value which is far the player should move. I want to complete the movement in X seconds. I have tried many equations and ...
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### How To Program a fully controllable spring (Damped) motion

i'm working on a project that needs realistic 2D Animation, none linear motion you might say, i have tried many things such as Hermite Curve and a few other motions and in the end Spring Motion. ...
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### Self colliding cloth physics

I've previously simulated cloth using Verlet integration but couldn't successfully get the cloth to collide with itself in an efficient way. The reason being is because I used a brute force algorithm ...
353 views

### How can I synchronize ocean waves over the network?

I've been performing a little bit of research in my spare time on ways to increase the interactivity of environments in a networked game or simulation. One of my areas of research is fluid-dynamics ...
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### How do you calculate the rotational velocity of a flying object?

When a arrow shaped object is fired it slowly adjusts it's rotation to match the direction it is moving. But what is the actual physics behind it? The question is: How many degrees does the ship ...
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### Calculating impulse propagation through a rigid body after a collision

I'm working on a game. I need to work out what the impulse is at different points on a body as a result of a collision. For example, in the following diagram, if there is a collision that results in ...
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### Predicting physics/trajectory for pool/billiards games

I'm thinking of making a quick proof of concept of a billiard-style game mechanic, where the player has perfect information of what is about to happen. Here's a good example: I'm only mildly ...
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### Implementing Separating Axis Theorem (SAT) and Minimum Translation Vector (MTV)

I was following codezealot's tutorial on SAT and MTV and trying to implement it myself but I've come a cropper when it comes to getting the correct MTV. Here is my example: (Cue pretty pictures...) ...
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### Physics for Android Game

I'm making a 2D game for the Android phone, one that involves falling balls. I want to use a physics engine to properly simulate the balls falling and hitting other objects. I'm currently using Phys2D,...
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### Pseudo-magnet implementation with chipmunk

How should I go about implementing "natural" magnet on a certain body in chipmunk space? Context is of simple bodies lying in the space (think chessboard). When one of the figures is activated as a ...
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### How to apply friction vector to acceleration in top-down 2D game?

I'm making a top-down view 2D RPG game, meaning the player can move in any direction on a 2D plane, and I'm trying to implement a somewhat realistic non-orthogonal acceleration/friction physics model ...
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### Is this a correct backward Euler implementation?

I want to simulate a mechanic object like this: init acceleration a; init velocity v; init position x; loop { get delta time dt; v = v + a*dt; x = x + v*dt; } I use the velocity (which is the ...
255 views

### Pathfinding with inertia

I'm currently working for pathfinding for a game where units are moving, but they have inertia. Most typical pathfinding algorithms (A*, Djikastra, etc.) are simply designed to minimize the length of ...