# Tagged Questions

Collision detection is the determination of whether or not two or more entities make contact with each other during gameplay.

541 views

### How to detect if a ball will collide with another, and the normal vector of the collision?

So I have a 2D game involving balls (circles) colliding. I want to be able to detect if two balls will collide before it happens, and the normal vector of the collision if a collision is going to ...
320 views

### How do you prevent AABBs from passing through each other?

I know what an AABB is, but I don't know how you would check for collision with an object that is going really fast. If an object goes fast enough, it can skip over other bounding boxes without it ...
1k views

### Using uniform grids for collision detection - Efficient way to keep track of what a cell contains

I was looking for an efficient way to implement collision detection in a 2D game. A way that won't result in an O(n^2) level of complexity. A lot of people recommend to use Uniform Grids for this ...
2k views

### How do I detect multiple sprite collisions when there are >10 sprites?

I making a small program to animate the astar algorithm. If you look at the image, there are lots of yellow cars moving around. Those can collide at any moment, could be just one or all of them could ...
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### 3D RTS pathfinding

I understand the A* algorithm, but I have some trouble doing it in 3D to suit the needs of my RTS Basically, in the game I'm making, there will be agents with different sizes of OBB collision boxes. ...
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### How does the SAT collision detection algorithm work

There are a lot of tutorials and sample code available showing how to implement the SAT collision detection algorithm. But can someone explain, without math or code, what are the general principls ...
771 views

### Collision Detection Problems

So I'm making a 2D tile based game but I can't quite get the collisions working properly. I've taken the code from the Platformer Sample and implemented it into my game as seen below. One problem I'm ...
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### Collision detection in libgdx

I am currently writing a little zelda like game and have a little bit of a problem with collision detection. It works but the the character stands to far away from the object. Here is my player ...
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### Tools to generate convex collision geometry

Does anyone know tools to generate convex collision geometry from given 3D model? For example, UDK's Static Mesh Editor can do this; Valve instead recommends to use smoothing in 3D editor. Desired ...
3k views

### How to detect which edges of a rectange touch when they collide in iOS

I'm creating a basic "game" in iOS 4.1. The premise is simple, there is a green rectangle ("disk") that moves/bounces around the screen, and red rectangle ("bump") that is stationary. The user can ...
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### Storing rigid body collision shapes in local or world coordinates

I'm writing the beginnings of a lightweight 2d rigid body engine (in javascript, as a hobby project), and i'm debating whether to store collision shapes in local or in (updated as needed) world ...
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### How to detect screen boundary using AndEngine GLES1?

I am using the AnalogOnScreenControl to move my sprite around the screen. I would like to restrict the sprite so it can not move outside the screen boundaries. I have tried putting a line at the ...
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### How can we match polygon data structure with a background image

I am referring to this fireball game. The ball will collide with background, which is in polygon form. I was wondering, how I can match my polygon data structure with the background image. Say, I ...
166 views

### AABB collision resolution issues

I'm trying to make a character collide with some tiled terrain. I have an issue with the collision resolution, and after days of shooting in the dark ant not finding any relevant help online, I'm no ...
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### Voxel terrain collision detection with AABBs

I'm working on implementing collision detection on voxel terrain (Like Minecraft) with AABBS. Right now, I have it so I can tell if a point is within a voxel or not, I do this by having a 2D byte ...
491 views

### JBullet - Detecting when 2 objects collide?

How can I detect when 2 collision objects collide with JBullet? Currently, all body types are going to be of type RigidBody. I have quite literally been trying to find the answer of this for over 2 ...
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### How can I determine which direction a 2D collision is occurring from?

The problem is as follows: Think 2D Zelda (Links Awakening, A Link to the Past) style movement where you can run into walls from any of the four cardinal directions, or basically up, down, left, and ...
3k views

### Platformer raycast collision detection

I'm using Unity to create a 2D platformer. For collision detection, I'm using raycasting to detect any possible collisions with specific collision layers, and adjusting the desired delta x & y ...
1k views

### Collision detection optimization for a top down shooter

I'm relatively new to game development and have been trying to learn how collision detection is coded. I mostly work with Actionscript 3, but I'm learning C++ on the side. I've been wondering how "...
2k views

### implementing collision detection and handling for tiled 2D world with smooth wall sliding

Im using SFML 2.1 for graphics and my game structure follows SFML book quite closely (SceneGraph implementation etc) My world consists mostly of characters (around 1-400, moving around) and tiles (...
298 views

### Roguelike 2D Collision Detection

I'm just a normal guy trying to do some basic collision detection but I suck at it. I either get stuck in a wall or I go in reverse in the wrong direction trying to update the player position to a non ...
2k views

### Effects of collisons: broken glass, damaged cars, how are they created?

My question is related in particular to achieving the effects of collision in game engine, how is this done? I have searched a bit, read from the internet and went through a few tutorials, and saw ...
1k views

### Closest point on an ellipsoid

I need to know how to get the closest point on the surface of an ellipsoid to another point. I had an idea, but apparently i was wrong, and oversimplfying. What i did was squash the ellipsoid and ...
1k views

### Collision Filtering in Box2D

I have four bodies in my Box2D World. Each are polygon shape, with some physics parameters. Now when the game start, I need one of the bodies from the World (BodyA) to not be allowed to collide with ...
3k views

### Why do we use physics engines for collision testing or raycasting?

There is a thing I don't understand about game engines: why it is so common to use physics engines to do raycasting or collision testing? Say that you have a 3D scene loaded in your scene manager (...
1k views

### I need help with 2D collision response (of stacking rotating polygons, with friction and gravity, for a game)

Hi I am looking for suggestions on how to write a collision response for game programming purpose (so not a scientific simulation). I am dealing with 2D polygons that are rotating, and I want them to ...
2k views

### Collision Detection problems in Voxel Engine (XNA)

I am creating a minecraft like terrain engine in XNA and have had some collision problems for quite some time. I have checked and changed my code based on other peoples collision code and I still have ...
4k views

### Circle-Rectangle collision resolution

I have a non axis aligned rectangle, like a car, in my game. I have to check and resolve the collision between the rectangle and circle, which is stationary. I have found lots of ways to determine ...
2k views

### Create bullet physics rigid body along the vertices of a blender model

I am working on my first 3D game, for iphone, and I am using Blender to create models, Cocos3D game engine and Bullet for physics simulation. I am trying to learn the use of physics engine. What I ...
6k views

### When would a mesh collider be better than primitive colliders

I have been reading through the Unity Manual and have come across some interesting information about mesh colliders and primitive colliders. It got me wondering if using many primitive colliders would ...
5k views

### How do I detect pixel-level collision using andEngine?

I'm developing a game for Android using andEngine, and I need to detect collisions only when two objects visually collide (not in blank space of the image). In J2ME, I'm able to do that using ...
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### Fast 2D collision detection in an unbounded space

I'm trying to do collision detection on a large number of entities of greatly varying size in an unbounded space. The entities are circles, so it's relatively easy to check if two are colliding. ...
642 views

### Collision detection - make sure the player touches the object exactly

I know this is really something I should be able to figure out on my own, but a solution is evading me. Okay, here are a few relevant parts of my code. bool Game::Col(int x1,int y1,int w1,int h1, ...
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### How do I detect a line collison in LIBGDX?

I am drawing a continuous line using Pixmap. I want to check for a collision / intersection of my line with the already drawn line.
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### Collision detection between axis-aligned bounding box and bitmap (pixel perfect) terrain

Working on a Worms-type game, I have my objects in bounding boxes and they sit on the pixel terrain. Currently I am able to successfully do the collision detection for objects when they enter the ...
3k views

### 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 ...
144 views

### Rendering after interpolating, renders inside/outside other objects

So, we're working out our interpolated render-coordinates during our render call and it's doing a fantastic job of smoothing everything out. All is great and collision detection is working to a ...
4k views

### Unity, changing gravity game & stopping character when he hit a wall

i am currently working on a 2d puzzle game in the unity engine. One of the aspect of this game is the possibility to rotate the level of 90°. It also rotate the gravity. The main character is not ...
1k views

### Collision Detection for a 2D RPG

First of all, I have done some research on this topic before asking, and I'm asking this question as a mean to get some opinions on this topic, so I don't make a decision only on my own, but taking ...
995 views

### Tile based map and collision; getting stuck

I'm trying to make my character move around a tile map with collisions. Everything works fine except for one thing. I show you a picture with the problem: http://i.stack.imgur.com/ZWI7x.jpg That is, ...
811 views

### Checking Collisions In 2D Platformer With Tiles

My team and I are developing a 2D platformer with C++/SDL/OpenGL, and we already defined a collision system, but we have a problem checking collisions with the tilemap. The tiles of the tilemap are ...
1k views

### 2D platformer multiple rectangle collision cause jitter

I posted this question two weeks ago: 2D platformer corner collision and I implemented NoobsArePeople2's solution. Problem is, when player intersects two rectangles that are inside each other, he ...
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### Tile map collision is not working properly

I am having problems setting collision between my sprite and the tiles. I have only done the code for colision for moving upwards but some places on the map it moves up and some places it doesn't. ...
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### How can I know in which direction 2 balls will go in billiard game?

When a ball is struck, how can we know in which direction both balls will go when ball is struck? I know the angle at which the ball strikes the other ball matters, but how can we calculate that angle?...
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### Entity to tile collision detection (C++, SDL)

I'm currently trying to handle collisions between entities and a tilemap, but I've hit a problem. My tiles are stored simply as integer tile IDs in a multidimensional array, and I wanted to perform a ...
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### Cell height with heightmap for collision detection

Hello everyone I'm programming a game with c++ and openGL. My world is generated from a heightmap (100x100 matrix with values 0-255) and now I need a function that returns the actual height based on ...
2k views

### How can I cancel a contact in a b2ContactListener?

To know when contacts happen we can derive from b2ContactListener and implement our own solution which is great. I'm wondering is there anyway we can cancel a contact, that is to say when we hit begin ...
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### Randomly spawning bitmaps on cnvas

I need some ideas in order to finish algorithm. I'm randomly placing objects (bitmaps) on canvas without overlapping. Time needed to finish it is my problem. When I need to spawn for example 80% of ...