# Tagged Questions

A shape made up of a connected set of points that are all equal distance from a center point.

5k 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

### Circle inside circle collision

In one of my projects I have a game area in the shape of a circle. Inside this circle another small circle is moving around. What I want to do is keep the small circle from moving outside the bigger ...
1k views

### Circular Bullet Spread not Even

I'm creating a bullet shooter much in the style of Touhou. Right now I want to have a very simple circular shot being fired from the enemy. However, the spacing is very uneven, which isn't very good ...
8k views

### How do I find the intersections between colliding circles?

I want to find whether 2 circles with radii r1 and r2 intersect, and if so, where they do so. Is there a simple solution?
717 views

### HLSL Circle all white

I have been trying to get my shader code (HLSL) to draw a simple circle but after a day and a half I am getting nowhere. It seems people are using the x^2 + y^2 = r^2 and remap texcoords but I only ...
206 views

### Drawing circles at the background of a 3D scene and updating their size

So, here is what I am trying to do in Unity 5 (using C#). I want to draw a a 2D circle at the background of a 3D scene and apply a texture/image to fill it. Just like it would be if the circle was in ...
728 views

### Animation of moving circle by square's outer surface

I want to make this animation in OpenGL, here I attached a simple gif how I want it to looks like: Main problem is that I can not figure out how to move by corner - circle should smoothly move by ...
8k views

### How to draw a smooth circle in Android using OpenGL?

I am learning about OpenGL API on Android. I just drew a circle. Below is the code I used. public class MyGLBall { private int points=360; private float vertices[]={0.0f,0.0f,0.0f}; private ...
1k views

### How to bounce a 2d point particle off of a circular edge

In a prototype I'm building, a particle can spawn anywhere within a larger, confining circle. Important to note is that the particle will not spawn in the origin of the larger circle, but anywhere ...
8k views

### Drawing a circle in OpenGL ES Android, squiggly boundaries

I am new to OpenGL ES and facing a hard time drawing a circle on my GLSurfaceView. Here's what I have so far. The circle class public class MyGLBall { private int points=40; private float ...
175 views

### How can I merge the corners of fractally-generated borders so they look natural?

I'm using a fractal generator to generate borders around a rectangular area. It works great, but my problem is with corners. A naive implementation when the left border overlaps the top border: ...
5k views

### OpenGL GL_LINE_STRIP produces arcs with visible line edges

Another member mentioned an issue while drawing arcs with GL_LINE_STRIP. He has GL_LINE_SMOOTH enabled. The question is, how could he avoid the tiny gaps between vertices without increasing their ...
1k views

### In Box2D, how can I check for bodies within a circle?

I'm trying to sample random positions to find one that is sufficiently far from other bodies. Hence I'd need to test for bodies within a given circle. So far, I've used b2World::QueryAABB around my ...
117 views

### Moving objects in a circular path, and also moving the whole group

I have 8 elements distributed in a circle, with a common center. All of them move along a circular path, just like the poster in this question asked: Moving an object in a circular path This solves ...
375 views

### How to “merge” multiple intersecting circles so that only the outer edges of each show?

In my RTS (In Unity) each unit or building has strategic circles in a similar fashion to SupCom. If you have multiple units or buildings selected it looks like the picture to the left. I want to make ...
296 views

### Intersection between moving circle and some squares

I'm developing a 2D game made of squares. What I need to do is check if a circle collides with any of the squares as it moves. I have a raycast function to check the same idea, but using a point. I ...
733 views

### How can I make a spline out of three points that define circular arc?

I was looking at the descriptions of various curve techniques here and noticed the mention of circular arcs. I want to implement something like this, but I'm not quite sure what the correct formula to ...
164 views

### How to calculate max region/area of 2d circles?

I have some 2d circles on a plane, each has its own minRadius and maxRadius. When two circles collides, both of them will shrink their radius, so the actual radius of a circle is in range [minRadius, ...
134 views

### Draw 3D ellipse in monogame/xna

I am programming a 3d solar system (simulator). To describe the path of a planet I wanted to add 3D rectangles.. and draw them. But this ; no surprise; decreased the frame rate extremly. Also it does ...
216 views

### 2D multiple circle collision response

I'm trying to implement simple 2D circle collision system. There are circles with different radiuses and velocities (the larger the circle the slower it is). Contrary to all the questions on the Stack,...
98 views

### Detect collision that happen between frames, between slices of moving, rotating circles?

To detect a collision between two circles, we check if the distance between their centers is smaller than the sum of their radii. To detect a collision between a slice (in this case half) of a circle ...
330 views

So I've been scouring the interwebs for a couple of days with regards to how to implement sprite masking in XNA 4 and C#. Coming from a pet project I did in Flash, this was pretty easy as masks are ...
124 views

### Objective-C SpriteKit – How to make a circle of buttons

I have some code in a project already, but I'd like to change it up a bit. Currently, my code creates an empty node called _buttonLayer and then create some buttons to add to it. My buttons start from ...
1k views

### How to set speed of circular motion

Edit 2 - clarification Just to clarify, the issue I have at the moment is how I specify a time (in seconds) for a complete revolution to occur. My delta is fixed and is 1/ticks per second (1/60). ...
3k views

### Collision between AABB and Circle

I'm programming collision systems for a 2D game engine. The idea is that different systems can interact with each other. So one of the cases would be check collisions between axis aligned bounding box ...
585 views

### How to handle circle penetration

I've been working on cirlce to circle collision and have gotten the intersection method working correctly, but I'm having problems using the returned values to actually seperate the circles from one ...
674 views

### How does this circle collision detection math work?

I'm going through the wildbunny blog to learn about collision detection. I'm confused about how the vectors he's talking about come into play. Here's the part that confuses me: p = ||A-B|| – (r1+...
463 views

### How do I resolve a collision of a circle with two rectangle corners?

I'm writing a simple non-physical one-circle-to-many-rectangles collision detector/resolver. For collision detection, I'm using a very common algorithm, and it's working pretty well. For collision ...
754 views

### Circular movement - eliminating speed ups near Y = 0

I have a basic algorithm to rotate an enemy around a 200 unit radius circle with center 0. This is how I'm achieving that: if (position.Y <= 0 && position.X > -200) { position.X -= 2;...
4k views

### How to draw a circle with WebGL using GL_POINTS [closed]

I'm trying to draw a circle using simple vertices points and a big gl_PointSize value. I found this example and try to reproduce it on WebGL with no success.
68 views

### How to calculate Joystick margins/tresholds?

On Joystick that gives Float position values from -1 to 1 on either of x and y axis, how to implement proper math, that adds "lower" and "higher" circular margin? For example if lower margin is 25% ...
268 views

### How do I make circles bounce off each other realistically?

I'm trying to create bouncing balls with realistic physics. At the moment, when the balls hit each other, they bounce back in the same direction they came from. How do I make them more realistic? I ...
594 views

### Bouncing off a circular Boundary with multiple balls?

I am making a game like this : Yellow Smiley has to escape from red smileys, when yellow smiley hits the boundary game is over, when red smileys hit the boundary they should bounce back with the ...
645 views

### Tangent to a circle through a point

I'm trying to figure out how to calculate the following angle: I know center (p1) and radius (r) of a circle. Given a point p3 I want to calculate the angle a such as the tangent (tan) of the circle ...
34 views

### Circular Movement

if (Keyboard.isKeyDown(Keyboard.KEY_D)) { if (i < 360) { setX((float) (groundState.getX() + groundState.getRadius() * Math.cos(Clock.delta() * i))); setY((float) (groundState....
57 views

### 2d Circle different ARC's Collision detection

The way to detect collision between 2 circles or circle and line . using trigonometry But now i like be able to detect which part of the circle arcs im hitting , for example i divided my circle to 4 ...
56 views

### GJK algorithm in case of circle and polygon?

I wonder if it's possible to modify GJK so I can use it to detect collision between circle and n points polygon. I implemented for polygon and polygon before, and I tried modifying the support ...
66 views

### Revert to closest non intersecting position

First, let me start by saying: Please forgive me if this question have already been asked. I've tried to search but didn't find any solution. (It might be due to my lack of terms). I have two ...
13k views

### How do I make a circular hole inside an editable poly without boolean operations?

I have created a rectangle, then converted it into an editable poly. Then I created a circle and converted it to editable poly too. How to make it so that that the circle becomes a hole in the ...
25 views

### Object orbitting 2D circle java

I'm using this code to make a square that orbits a circle . When i use it however the rect(); is quite far away from the circumference of the circle, i would like to make it closer. All variables are ...
130 views

### How does collisions caculates when developing game in Build an HTML5 Game book

I don't understand authors login when calculating collisions between two circles (bubbles). Here is the Calculating collisions section. Author writes: The bubble being fired follows a set of ...
642 views

### How to solve the overlap of two circles that collide

I have two circles , one of the circles is static the other is moving around. I have a method that checks whether the two circles collide. How to make the two circles don't overlap when colliding? ...
419 views

### Revolve FlxSprites Around a Central FlxSprite in Flash Game made with Flixel

I have been working on a Flash game made in Flash Builder using the Flixel library. I have been trying to dynamically create a group of FlxSprites , and revolve them around a player controlled class ...
772 views

### Why circles are not created if small?

I have changed the scale to my own and now I cant create any object, including circle, if it is of the size which is normal for my scale. I am to create big object first and then modify it to smaller ...
22 views

### Resizing a procedurally generated arc mesh

I have a script that generates a mesh representing a 2D arc. This arc is generated when the game starts based on a size (radians), width, etc... I would like to know if there's any fast way to resize ...
210 views

### LibGDX collision with rectangle and circle

I have 2 objects, A and B, both are classes with only values, so positions and dimensions are only values (float posX,posY). I have a render class which render A and B with shapeRenderer; A is ...
90 views

### Grab all tiles within a radius?

I'm working on a 2D tile based game. I want NPC's to be able to destroy tiles, and ideally I would have a function, which takes a central x,y and then based upon a circular area from that point (...