# 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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### Custom Physics: Preventing objects from losing velocity in certain situation

Illustration: http://s22.postimg.org/7agd30vap/Untitled.png So the little box is my character. The red arrow shows the current velocity(Some force to right + gravity). Below it are 2 blocks which has ...
162 views

### 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 ...
229 views

### Can I make a character solid but not lose non-physics behaviour?

My character can walk around in the world, but walks through other objects, for example a cylinder (stand-in for a cannon). To fix this I added a capsule collider to each of the character and cylinder,...
215 views

### Mobile: Physics and movement actions

I've been using spritekit for a while for a few small games. One thing I've noticed is that spritekit is the first game framework I've used that allows me to apply move actions to physics bodies. (...
287 views

### 2D Enemy AI reacting to sound

I'm currently working on a 2D top-down survival game and I'm trying to figure out a good method for enemies to detect player sounds. For instance - if the player fires his gun it should play a sound (...
405 views

### How to know when all 2d rigid bodies have stopped in unity3d?

Is there anyway to know if all 2d rigid bodies in untiy 3d phisics world have stopped?
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### Moving objects smoothly, bad perfomance

I just finished developing my mini-game on Android and I got some questions about perfomance and generally "how to": If I have 25+ objects on the creeen (just a polygon with 7-8 angles) its starts to ...
408 views

### How do I convert a partially transparent image into polygons?

I'm using GLEE2D, a level editor allowing me to import images, scale them, rotate them, and position them onto layers and export the data into XML format. However, it does not tell me objects' ...
70 views

### How to predict physics movement [duplicate]

How to predict the movement of the body when a force is applied on it like in the https://play.google.com/store/apps/details?id=com.game.basketballshoot I have attached screen shot as reference.
1k views

### 2D Collision in JavaFX - Bad accuracy with .intersects()

I have several Shape objects - Circle, Rectangle and Polygon. I use the built-in .intersects(Bounds1, Bounds2) method to detect collision but it's quite inaccurate. Circle c1 = new Circle(20); ...
115 views

### How to make character gain acceleration?

I want to create more realistic physics for my 2D games. Currently, the character and the other game objects in my games start moving instantly (achieve maximum speed instantly) and stop instantly (...
3k views

### Movement and rotation of bodies in top down game

We are developing a 2D top down game with libgdx using the included box2d as physics engine. We don't want our bodies to accelerate but to instantly move with the wanted velocity. The bodies are ...
426 views

### How to design basic physics and movement behavior for 2D platformer?

I want to make a simple 2D platformer. I know some basic 2D physics and how to implement them in a game. How to make a character jump, accelerate, decelerate, etc. But I have no idea how to actually ...
122 views

### Calculating the point(s) at which two moving objects are a certain distance from each other

Problem This is similar to a Closest Point of Approach calculation, but instead of the closest point(s), I want the points at which the objects are a given distance away from each other. (Imagine two ...
181 views

### How do you calculate the rate of rotation using the accelerometer values in Android for a particular axis?

I am developing a simple game which involves a character moving up and down only along the Y axis. Currently I am using the accelerometer readings to change the Y velocity of the character. The game ...
160 views

### How to apply steering to a physics body correctly when using a physics engine?

I have a top down 2d game that uses a physics engine (Farseer). I'm using the standard steering behaviors to make the AI move around but I'm not sure the correct way to take the so called "steering ...
940 views

### Conceptual - What is the optimal way to combine steering behaviors with rigid body physics?

I am working on a simple 3D space simulator that makes use of the Bullet physics engine. The spaceships are rigid bodies that have a mass and hitbox so that they can be considered for collisions. At ...
26 views

### Handling gyroscope data

I'm working on a mobile game that allows user to rotate player around an axis using accelerometer. In addition to that, to allow fast, almost instant, rotation I thought of using gyro data. It seems ...
359 views

### Calculate point of circle–circle collision between frames

I need to find the exact XY coordinate where a circle collides with another circle calculated between frames. This means that I take the coordinate of the moving circle on the previous frame and take ...
3k views

### Is a separate thread for game loop compulsory for simple games?

I am new to game development. In order to learn I am recreating this game on android platform. You can observe the game-play video at the above link. It is a simple game. I have read a lot of ...
291 views

### How can I calculate force and acceleration?

I have problem of calculating the movement of the object. At the moment, I have a vectors calculated from the center of the screen minus the position of the object. direction vector = centerScreen -...
237 views

### Artillery Simulation [duplicate]

I need some help on a simulation of an Artillery like this one https://www.youtube.com/watch?v=YktWSKo_UbA. I cant figure out how to make the "tomato" to get to the selected spot. Where can I get ...
301 views

### How to impale and stack targets correctly according to the collider and its coordinate?

I'm making another simple game, a catch game, where a spawning target game object must be captured using a skewer to impale it. Here how: At the start, the falling object (in red) will fall in a ...
287 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 ...
202 views

### Relative Position/Rotation calculation

I have 2 objects each with a 3x3 Matrix (Orientation) and a Vector3 (Translation). Both are relative to world coordinates. How do I calculate the position and orientation of object B in relation to ...
1k views

### Algorithm for randomly generating reachable platforms

I want to randomly generate reachable platforms on the fly for a 2D game. Right now, I am just creating platforms at random x,y positions. Only 4 platforms can exist at once, so once the 5th one is ...
5k views

### How do I make a character capable of walking on walls?

I am trying to get a character to move like a spider: Given a rising slope which a ball would normally not be able to roll up, the spider would slowly crawl up. Similarly, given a mid-air rectangular ...
561 views

### How do I make a cube move by rolling?

I am learning jMonkeyEngine by making some small games with it. I have a simple rectangular cube that I want the player to be able to roll around the game world. When he presses the arrow keys, the ...
421 views

### What are the parameters for btHingeConstraint::setLimit

What does each parameter in btHingeConstraint::setLimit do to the hinge constraint? void btHingeConstraint::setLimit ( btScalar low, btScalar high, btScalar _softness = ...
776 views

### How do I determine a good path for 2D artillery projectiles?

I'm building a little "tank wars" game (like this one). I understand the math, and I am able to define a parabola from the launcher to the objective I want to reach. The parabola depends on the ...
698 views

### Calculating impulse with multiple collision points

In my amateur 2D rigid body physics engine for a game I react on collisions between two bodies with an impulse j (formula 11) as explained here. To calculate this impulse I need one contact point P ...
1k views

### Planet gravity? [duplicate]

I am trying to make a game with the Phaser game engine and would like to implement some sort of planetary gravity. Essentially I just want the player to be able to walk on a circle or orbit a point. I ...
369 views

### Calculating/Predicting a way

I'm just starting with physics, so I'm not always sure about what I'm doing. It's a 2D project but I'm using 3D physical objects like SphereCollider etc.. What I have: Objects floating in space and ...
5k views

### Collider2D and Rigidbody2D, how do they work?

I have been learning JavaScript and Unity for a week now. I learned how to make Cube as a Ground and another Cube as a player and I used this code to make the Player Cube move forward and backward and ...
760 views

### 3D-Physics of a Rubber Ball (Squash)

I'm trying to simulate the environment on a Squash Court on Android with my own physics and using OpenGL for visualization. Basically, its about a rubber ball bouncing around in 3d, not just on the ...
317 views

### Ice sliding physics

I am trying to implement ice sliding physics on a plane for my game. There are a lot of N64 games that implemented them perfectly well, like Banjo-Kazooie, Super Mario 64, Zelda: OoT and MM, etc. ...
606 views

### How do I implement swipe-to-throw in Andengine?

I have a ball sprite and I apply physics to it when the user swipes on it. I'd like the ball to start moving in the direction of the swipe, similarly to how Paper Toss works. How can I do this?
138 views

### Bullet3: Issue with applying force once an object is at rest

I just started using bullet and I'm having an issue where once my rigid body is at reset at the floor it won't move when I apply a force to it. I have created a small demo to show this using the ...
41 views

### Ground hitting system [closed]

I want to know how to make character hit ground and lose health. For example: when character is falling of one meter he losing only a small part of his health, and when he's falling of 10 metters he ...
385 views

### How do I simulate a trampoline?

I'm quite new to game development. I was pretty impressed with the elastic effect I saw in this flash game when the ball hits the trampolines and I'm wondering how to recreate it. I've done some ...
751 views

### Inertia Tensor and World Coordinate conversion

I understand that the inertia tensor is basically a 3x3 matrix. I'm modelling a cube, and the inertia tensor for this shape has values for moment of inertia on the main diagonal of the matrix. All the ...
253 views

### Is there a benefit to applying forces to my camera?

I have implemented a camera system and a rudimentary physics system. I now have a decision to make regarding steering the camera: Option 1 - Update the camera movement directly. eg. position (0, 0, ...
4k views

### Get GameObject to bounce of colliders [duplicate]

I am making a Atari Breakout game with unitys 2d tools and I need to get the ball to bounce of colliders in the scene. If you havent played the game before how it works is if the ball hits the wall at ...
128 views

### Trying to make sprite float up and down [closed]

Using LibGDX + Box2D and my understanding of the answer posted from this question: Here I apply the following impulse: // modify sprite's Box2d Body object int a = 8; // amplitude int f = 1; // ...
410 views

### Collision detection via adjacent tiles - sprite too big

I have managed to create a collision detection system for my tile-based jump'n'run game (written in C++/SFML), where I check on each update what values the surrounding tiles of the player contain and ...
4k views

### Can someone explain Flappy Bird's physics to me? [closed]

I am having a difficult time trying to understand the Flappy Bird physics. I know it seems simple but I kind of suck at math. I am trying to see if I can make a simple game like this but it is just ...
61 views

### Proper Order to Process Each Frame

I'm writing a rudimentary 2D engine and am wondering what the proper or generally accepted order is for handling graphics, user input, sounds, and then other systems like physics. If you have written ...
3k views

### Moving rigidbody2d towards mouse click using AddForce

I cant get my rigidbody2d game object to move to where i click the mouse. The first click works. The object travels to the mouse click and stops. But the second time (or the third time) i click the ...