# Questions tagged [collision-detection]

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

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### Different collision effects on different objects

I'm a beginner to Corona and game development. I am using a variety of objects in my game. On collision, they all perform the same function. I want them to do different things, and also want some ...
2k views

### Make my NPC “see” gameobjects around him in Unity

I have a walking NPC that will "see" the wall in front or behind him (2d gameplay) and that will react accordingly. I was thinking to attach him to an invisible collider that would react to objects ...
883 views

### Ball bouncing within polygon

I saw there are quite a number of articles and sample code regarding ball bouncing within a rectangle. Is there any articles or sample code regarding ball bouncing within a polygon? I try to look ...
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### 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 ...
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### Have a simple enemy detecting he touch a wall to make him stop/turn around

I am doing a very simple scene with a cube sliding on the "ground". Once the cube reach a wall, he is blocked. I want to detect the wall to make the cube go in the other direction. I used ...
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### Degrees to Coordinates

Hey, I'm creating my second game ever, but this time - using Java. Before I used Pascal and CRT module! =D It's 2D game where you need to drag the ball with mouse from location A to location B. Right ...
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### Operations on multiple overlapping layers not working

Hi I am developing a game in android just like Farmville by Zinga. In that game we have to place elements in the diamond shaped field so the don't overlap each other. Now I did coding for placing the ...
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### How to create a realistic 2D Role-Playing game collision detection?

I’ve always wanted to create an old-fashionned 2D Role-Playing Game like Star Ocean, Final Fantasy, Sword of Mana and even the “Tales of” series, and I guess a lot of people do. But before even ...
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### Help with Collision of spawned object(postion fixed) with objects that there are translating on screen

Hey guys I am creating a game using Corona SDK and so coding it in Lua. So there are 2 separate functions, To translate the hit objects and change their color when they are tapped The link below is ...
6k views

### 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) ...
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### Flash AS3 Tower Defense Problem

I am working on a tower defense game in Flash. Right now most towers find the the nearest enemy in range (enemies are in an array), get the enemies coordinates, and fire a bullet. When it hits the ...
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### 2D Rope Collision Detection

I'm wanting to create a rope that can collide with objects like in the following youtube video: 2D Game Physics Rope I'm thinking that you implement the verlet integration which uses points and ...
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### Finding the point of collision

I'm writing a 2D rigid body simulator. The objects being simulated are convex polygons. My question involves how to decide on the "point" of collision, so that when I apply a response force, I can ...
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### 2d Ray intersection

I've recently picked up a class which creates 2D Rays and detects if the ray is intersecting any bounding boxes passed through it. ...
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### Collision Problems

I'm having some troubles with a 2D platformer type game (there's more to it, but that's all that matters for this question). I had collision with the platforms working fine, but if the character hit ...
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### A ball hits the corner, where will it deflect?

I need to brush up my trigonometry and hope you can help here with a simple mathematical model. Here is my model so far in the image attached. I am aware that the frame animation has other problems ...
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### Collision test solution for hack&slash game

I want to ask you what is the best way to deal with collisions in hack&slash game, I know that collisions must be very accurate. My first idea is to use sphere bounds ( I making hack&slash in ...
584 views

### XNA 2D Collision Detection without GetData()

I'm currently working on a Worms game which involves terrain deformation. I used to do it with .GetData(), modifying the color array, then using ...
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### Determining if a character is within the field of view in XNA

I'm trying to creating a field of view for the camera I'm making for a game. It rotates around a circle for 180 degrees while the head moves accordingly. I'm going to bound the field of view within an ...
2k views

### Are Loose Octrees Too Loose?

I've been reading Real-Time Collision Detection and for loose octrees it recommends expanding each node's AABB length by a factor of 2, making its expanded volume 8 times as large. I am surprised ...
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### Correct order of operations in a platformer game loop

I've run into an issue with my Mega Man engine, and the structure of my game loop is making it very difficult to fix. With Rush Jet, or any falling platform, Mega Man needs to stay attached to the ...
1k views

### Android collision detection of a 3d object based on a 2d projection

I am writing a game for android. We have an orthographic view setup, but the characters (ships, projectiles, etc). The enemies / characters will be able to rotate about the x axis. The problem is that ...
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### Quad trees/grid based collision - putting logic into action

First of all, I've only been writing my own game logic for a short while, so I apologize if this might seem straight forward. I've been reading a lot about quad trees and grid based collision ...
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### per pixel based collision detection

I was wondering if anyone had any ideas on how to get per pixel collision detection for the android. I saw that the andEngine has great collision detection on rotation as well but couldn't see where ...
1k views

### Moving objects colliding when using unalligned collision avoidance (steering)

I'm having trouble with unaligned collision avoidance for what I think is a rare case. I have set two objects to move towards each other but with a slight offset, so one of the objects is moving ...
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### Axis-Aligned Bounding Box- once rotated

Creating an AABB is simple. But, if the 3d model has become rotated, how do you update the AABB to become accurate? Or is the AABB supposed to be in local space?
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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 ...
3k views

### Points on lines where the two lines are the closest together

I'm trying to find the points on two lines where the two lines are the closest. I've implemented the following method (Points and Vectors are as you'd expect, and a Line consists of a Point on the ...
480 views

### x axis detection issues platformer starter kit

I've come across a problem with the collision detection code in the platformer starter kit for xna.It will send up the impassible flag on the x axis despite being nowhere near a wall in either ...
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### Collision Resolution

Hey all, I'm making a simple side-scrolling game, and I would appreciate some input! My collision detection system is a simple bounding box detection, so it's really easy to implement. However my ...
580 views

### Creating the “game space” for a 2D game

How does one setup the game space for a game so that obstacles can be spawned? Examples would be ice climber or the iphone doodle jump. Tile maps are limited in size and would need to change often if ...
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### Collision Detection in Java for a game

Im making a game in Java with a few other people but we are stuck on one part of it, making the collision detection. The game is an RPG and I know how to do the collision detection with the characters ...
2k views

### 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 ...
5k views

### 2D Platformer Collision Handling

I am trying to create a 2D platformer (Mario-type) game and I am some having some issues with handling collisions properly. I am writing this game in C++, using SDL for input, image loading, font ...
1k views

### Projectiles in tile mapped turn-based tactics game?

I am planning to make a Laser Squad clone and I think I have most of the aspects covered. But the major headache is the projectiles shot/thrown. The easy way would be to figure out the probability of ...
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### Multiple Sprites using foreach Collison Detection in XNA (C#)

Back again from my last question. Now I was curious I use a foreach statement to use the same shot class. How would I go about doing collison detection. I used the tutorial here on how to shoot a ...
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### Voronoi regions of a (convex) polygon

I'm looking to add circle-polygon collisions to my Separating Axis Theorem collision detection. The metanet software tutorial (http://www.metanetsoftware.com/technique/tutorialA.html#section3) on SAT,...
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### Tile-based 2D collision detection problems

I'm trying to follow this tutorial http://www.tonypa.pri.ee/tbw/tut05.html to implement real-time collisions in a tile-based world. I find the center coordinates of my entities thanks to these ...
812 views

### Breakout clone, how to handle/design for collision detection/physics between objects?

I'm working on a breakout clone, and I wish to create some realistic physics effects for collision - angles on the paddle should allow the ball to bounce, as well as doing curve balls etc. I could use ...
2k views

### Collision detection of convex shapes on voxel terrain

I have some standard convex shapes (cubes, capsules) on a voxel terrain. It is very easy to detect single vertex collisions. However, it becomes computationally expensive when many vertices are ...
7k views

### 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 ...
8k views

### How do I test if a circle and concave polygon intersect?

I have a polygon (sometimes convex, but often concave), and a bunch of circles with different radii. How can I find out if a circle is intersecting/overlapping with the polygon? I could split my ...
2k views

### Pong Collision Help in C# w/ XNA

Edit: My goal is to have it function like this: Ball hits 1st Quarter = rebounds higher (aka Y++) Ball hits 2nd Quarter = rebounds higher (using random value) Ball hits 3rd Quarter = rebounds lower (...
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### How to determine which cells in a grid intersect with a given triangle?

I'm currently writing a 2D AI simulation, but I'm not completely certain how to check whether the position of an agent is within the field of view of another. Currently, my world partitioning is ...
458 views

### How to detect and collide two elastic line segments?

There are 4 moving physical nodes in 3D space. They are paired with two elastic line segments / strings (1 <-> 2; 3 <-> 4). Part I: How to detect the collision of two segments? Part II: On the ...
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### problem with frustum AABB culling in DirectX

I am currently working on a project with a few friends, and I am trying to get frustum culling working. Every single tutorial or article I go to shows that my math is correct and that this should be ...
299 views

### Collision filtering by object, team

I am looking for a good method to determine which objects will be considered for collision with other objects. My current idea is that each object has the following properties: alwaysCollidesWith = [...
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 ...