# Tagged Questions

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

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### 2D Platformer Collisions

I've basically asked this question before, and I know it's been asked probably a billion times, but I still can't seem to do it. All I want to know is how I should go about doing basic 4-way, ...
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### Isometric Collision Detection

I am having some issues with trying to detect collision of two isometric tile. I have tried plotting the lines between each point on the tile and then checking for line intercepts however that didn't ...
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### How to handle pixel-perfect collision detection with rotation?

Does anyone have any ideas how to go about achieving rotational pixel-perfect collision detection with Bitmaps in Android? Or in general for that matter? I have pixel arrays currently but I don't know ...
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### 2D AABBs and resolving multiple collisions

Okay, so this is a problem I've been trying to figure out for quite some time. Mine is a 2D platformer game with a world made up of (usually) immobile tiles and mobile sprites, both of which use AABBs ...
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### Given a plane and a point, how can I determine which side of the plane the point is on?

Given the point Vector pos = new Vector(0.0, 0.20156815648078918, -78.30000305175781, 1.0); and the plane (triangle) Vector a = new Vector(-6.599999904632568, 0.0, -78.5, 1.0); Vector b = new ...
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### 2D object-aligned bounding-box intersection test

I have two object-aligned bounding boxes (i.e. not axis aligned, they rotate with the object). I'd like to know if two object-aligned boxes overlap. (Edit: note - I'm using an axis-aligned bounding ...
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### AABB - AABB Collision, which face do I hit?

To allow my objects to slide when they collide, I need to : Know which face of the AABB they collide with. Calculate the normal to that face. Return the normal and calculate the impulse that to ...
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### Minecraft-style player-gound collision detection

The title pretty much says it all... (Minecraft is a game consisting of evenly-spaced cubes for terrain, like voxels) Note: I am using C# XNA. I am pretty sure AABB is the way to go, yet I don't know ...
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### 2D collision-detection middleware

(This question was split off from http://gamedev.stackexchange.com/questions/3345/) Are there any recommendable middleware available for 2D collision detection? I believe I've heard that Box2D could ...
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### Collision Detection with SAT: False Collision for Diagonal Movement Towards Vertical Tile-Walls?

I'm developing my first tile-based 2D-game with Javascript. To learn the basics, I decided to write my own "game engine". I have successfully implemented collision detection using the separating axis ...
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### Side detection on Rectangle collision detection?

How can I determine which of the sides on a Rectangle that was hit by another Rectangle (or Circle if that's easier)? I originally tried creating 8 subrectangles for my main rectangle - one for each ...
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### How do I create a player movement system in Farseer?

My group of students is helping produce a a 2D platformer. We tried making a pixel-based collision system which fell through. Now I am trying this physics engine on for size and see new ways to create ...
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### Reflect angle on pong clone [duplicate]

I'm working on collision detection for a pong clone. I've calculated the angle of incidence but I can't find any information on how to specular reflect the angle I found. The code for calculating the ...
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### In Cocos2D, how do I check for collisions against an arbitrary user-drawn shape?

I want to detect a collision between a sprite and a user-generated shape of some sort. For example. There are 3 objects on the screen. The user takes their finger and draws an abnormal shape around 2 ...
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### Finding roots/zeros for collision detection?

For the most simple of 2D games, I have implemented a posteriori collision detection (overlapping rectangles) on the x/y Cartesian plane, but am now interested in understanding the basics of a priori ...
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### Ellipsoid v. Box collision detection

I'm trying to write some collision detection code. ATM i have the code properly resolving Ellipsoid v. Ellipsoid collisions, and Box v. Box collisions, but Ellipsoid v. Box collisions doesnt work. ...
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### Tile based collision detection failing when player is going too fast

I'm creating a side scroller and I'm have a problem with my collision detection. The collision detection works perfect when the player is falling at a constant speed, but when I implement more ...
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### SAT, How Do I Find The Penetration Vector?

I've just successfully implemented Separating Axis Theorem (SAT) in my game but I was wondering how do I find the penetration vector? I heard it can be useful for collision response. e.g. The harder ...
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### How to calculate the direction a ball must bounce

I have a tile engine I have made. I can detect collision between the ball(the player) and the tiles. When a collision is detected all the colliding tiles are stored inside a list. My question now is, ...
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### Game is responding very slowly?

I have a very simple app which removes buttons and re-adds buttons to certain layouts when a button is clicked. The problem is, this process is taking a very long time. My question is: How can I make ...
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### Ball vs 45-degree slope collision detection

I have a simple game in which the player moves a ball around. The ball bounces off of walls. Right now I have square walls(■) implemented: I use simple bounding-box collisions to check if the player ...
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### Circle-Rectangle collision in a tile map game

I am making a 2D tile map based putt-putt game. I have collision detection working between the ball and the walls of the map, although when the ball collides at the meeting point between 2 tiles I ...
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### box2d with lines

I have a very simple platform game builder and I've specified the ceilings, walls and floor as line segments. A line has a winding, or normal; you can determine the direction that a line should be ...
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### How do I create a custom collision map for clickable areas on a map?

Say I had a map like the one displayed above. What would be the best method of creating a collision map for each individual state where I can click individually?
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### New Vector Calculation for Elastic Collision of Circle and Fixed Rectangle

I am writing a fairly simple breakout-style game for Android phones. I have successfully detected the collisions between the ball(s) and bricks. The problem that I am having is in calculating the new ...
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### Collision Detection Efficiency

I've just written my first successful collision detection code, and it works great for a small scene of actors (player + 4-5 obstacles). However, I realize that since it checks every possible ...
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### libgdx - collision detection with tiled map java

currently, I am working on a 2d rpg game which is similar to final fantasy 1-4. I can load up a tiled map and the sprite can walk freely on the map. However, I will like to create a wall for it to ...
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### Collision detection between 2 irregular shapes

I need to implement a collision system for a vertical-shotter and the bullets can have any type of shape; i've implemented the shape class with an array of choords and an array of lines which have the ...
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### How are trajectories calculated and transmitted to other players in Multi-Player?

I play alot of COD4. And can see tracers for gunfire, missles, care packages fall from helicopters etc. There is alot of activity. I am curious to know the algorithm (at a high level) that manages ...
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### Updating entities in response to collisions - should this be in the collision-detection class or in the entity-updater class?

In a game I'm working on, there's a class responsible for collision detection. It's method detectCollisions(List<Entity> entities) is called from the main gameloop. The code to update the ...
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### Checking for collisions on a 3D heightmap

I have a 3D heightmap drawn using OpenGL (which isn't important). It's represented by a 2D array of height data. To draw this I go through the array using each point as a vertex. Three vertices are ...
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### Which axis-aligned line does an AABB collide with first?

I am making the collision resolution system for my 2d top-down game, and I managed to find a solution where I query which surfaces of other AABBs the current entity can collide with in the next frame. ...
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### Collisions not working as intended

I'm making a game, it's a terraria-like game, with 20x20 blocks, and you can place and remove those blocks. Now, I am trying to write collisions, but it isn't working as I want, the collision ...
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### missiles skip in collision detection

I'm trying to work on spaceinvader. I have problem that missiles or the bullets skip frames due to its fast speed. I tried to use the previous position of the bullet in the collision check, but still, ...
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### two balls stick together in a pool game? [closed]

when multiple collisions occur between balls..sometimes they stick together..mostly in cases of either of the balls having high velocity..can somebody explain pls
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### How to implement a 2d collision detection for Android

I am making a 2d space shooter using opengl ES. Can someone please show me how to implement a collision detection between the enemy ship and player ship. The code for the two classes are below: ...
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### How to avoid circular dependencies between Player and World?

I'm working on a 2D game where you can move up, down, left and right. I have essentially two game logic objects: Player: Has a position relative to the world World: Draws the map and the player So ...
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### Hexagon collision detection for fast moving objects?

A object has a position and a speed vector. Usually only the position is used to check if two objects collide, this is problematic for very fast moving objects as it can happen that the object moves ...
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### How to optimize the distance function?

While developing a reasonably simple RTS-like game, I noticed my distance calculations were causing an impact in performance. At all times, there are distance checks to know if a unit is in range to ...
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### How do I make A* agents avoid other agents?

I'm implementing a multi agent A* algorithm on a tile map. Agents move only in the X and Y axes. I avoid collisions between them by checking where the others are when calculating paths. It works fine ...
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### Triangle-triangle continuous collision detection

I am making a 3D game engine and I use continuous collision detection. I am using Sphere-Trees to cull primitive collision checks to a minimum. However, I'd like to perform continuous triangle-to-...
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### Collision Resolution

I know quite well how to check for collisions, but I don't know how to handle the collision in a good way. Simplified, if two objects collide I use some calculations to change the velocity direction. ...
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### Collision detection and response in an Entity System

More fun with an ES... Currently, I have a few systems: Renderer (Renderable attribute, Transform attribute) Motion (Movable attribute, Transform attribute, Renderable attribute [for bounding boxes,...
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### Collision detection with curves

I'm working on a 2D game in which I would like to do collision detection between a moving circle and some kind of static curves (maybe Bezier curves). Currently my game features only straight lines ...
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### How can I optimize a collision engine where order is significant and collision is conditional based on object group?

If this is your first time on this question, I suggest reading the pre-update part below first, then this part. Here's a synthesis of the problem, though: Basically, I have a collision detection ...
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### How do I handle Isometric collision detection?

I would like to make an isometric run-jump style platformer. The player should be able to jump on top of platforms above the floor, hit the side of objects etc. I'll be using a 2D game engine so I ...
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### Falling Blocks and complex shapes

I currently have a simple Tetris-like game and have come across a problem I cannot solve. Unlike Tetris where there is a single falling shape, I have multiple, potentially interlocking shapes that ...
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### Continuous Physics Engine's Collision Detection Techniques

I'm working on a purely continuous physics engine, and I need to choose algorithms for broad and narrow phase collision detection. "Purely continuous" means I never do intersection tests, but instead ...