# 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.

716 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 ...
375 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 ...
775 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 ...
320 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. ...
621 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 ...
388 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 ...
778 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 ...
257 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; // ...
439 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 ...
4k 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 ...
466 views

### How do you calculate the rotational velocity of a flying object?

When a arrow shaped object is fired it slowly adjusts it's rotation to match the direction it is moving. But what is the actual physics behind it? The question is: How many degrees does the ship ...
288 views

### Grid collision - finding the location of an entity in each box

I am trying to implement grid-based collision in a 2d game with moving circles. The canvas is 400x400 pixels. Below you can see the code for my Grid class. What I want it to do is check inside which ...
3k views

### Do two balls of different mass bounce different heights?

There are two balls and the only difference between them is the mass. Both are dropped from the same height on to the floor (static object with infinite mass), would both balls bounce up to the same ...
369 views

### Creating a vehicle using a physics engine [closed]

What is the theory behind creating a generic 3D vehicle in a physics engine? What I would like to know is what parts should I stick together to make the vehicle, how they parts should stick together, ...
1k views

### How to calculate a bounding rectangle of a polygon?

Polygon poly = new Polygon(); poly.getPoints().setAll(5d, 15d, 15d, 25d, 5d, 30d); How do I calculate the Polygon's height and width? There is no poly.getWidth() or poly.getHeight() method in javafx....
72 views

### Lateral Friction Phisics

I am trying to create a physics engine for my game, and need to cancel out any lateral velocity for when entities turn. I have tried to mimic this page's example, but it is not working. I have objects ...
929 views

### Can I jump from A to B?

I'm making some rudimentary AI for my side-scroller and I need to know whether an AI unit can reach point B from point A simply by taking a jump. Flight trajectory of my characters is a bit unusal as ...
755 views

### How to do collision detection for fluids in 3D? [closed]

Is there an algorithm or a technique which can detect the collision between 3D fluids? I currently treat my fluids as dynamic meshes. Is it possible to find collisions with these, or will I need a ...
2k views

### Gerstner wave function simplified?

The gerstner wave function is a commonly used method to calculate waves and simulate water in video games and movies or most 3d simulations. It is however quite complex so it is very hard for young ...
750 views

### 3d Water Simulation formula questions

I have created a Grid: At each point along the grid, is a vertex (Intersection Points): Each of these points has an x,y,z position. Vector3f(x,y,z). In an attempt to animate the grid into a group ...
129 views

### Where should the collision response/resolution code go?

I've got a collision response/resolution function that does the same for any pair of two entities. It's is in the World class right now. But right before that function is invoked, I have some entity-...
45 views

### Calculating Friction due to rotation from ball bounce? [duplicate]

In this question asked by codemonkey, The rotation will depend upon: upon impact, on: Initial Speed of the ball hitting the surface (magnitude of ball velocity vector) Friction co-efficient of ball ...
1k views

### How does this formula for generating water waves work?

I have been trying to implement the wave equation described in this paper ("Water Simulating in Computer Graphics," Kai Li and Liming Wu) in Java. Part of the paper discusses modeling waves as a sum ...
54 views

### How should I model rotation caused by bounce friction? [duplicate]

In my Java2D simulation, I have a disc which, when it bounces off the boundary of a 2D region, begins to rotate, as if it had gotten some spin from the wall. I'm having trouble relating the ...
795 views

### RK4, Derivatives, Understanding Game Physics

Gafferon Games has a great article on RK4 Integration for building physics simulations which can be found here: Integration Basics Personally my mathematics and physics knowledge could use ...
992 views

### Simple collision detection implementation [closed]

I'm making a game with C++ where the program extracts the lines out of an image (via openCV), stores them in an std::vector< std::vector< int > > and the builds a tile map out of it which is ...
2k views

### Slope polygon collider 2D causing box collider 2D to 'bump' while sliding on it

I'm doing procedural terrain generation. So far I've created the mesh, and attached a 2D polygon collider to it. The terrain is made up of hills going up and down. After doing so, I put a 2D rigid ...
351 views

### How to take into consideration gravity when moving AI

I'm making a 2D game. There is currently a helicopter flying around, controlled by the player. It's controlled using the arrow keys: UP, LEFT and RIGHT. It's speed along the y axis is dy, and speed ...
112 views

### How to apply logarithmic type formula for speed?

I want my character's speed to ramp up using somewhat of a logarithmic formula. I am confused about how specifically I would implement this. I want the character to move fast with a little movement as ...
1k views

### Applying a torque to a different centre of mass

In Unity I have an object with a circle collider attached to it and when I apply a torque to this object's rigidbody2D, it rotates as expected. However, I have now attached a sub-object to this object ...
683 views

### Does client side prediction sync with the server in the past?

I've spent some time now messing around and just trying to learn dead reckoning and client side prediction for the fun of it. Most of what I do doesn't need it, so i've never had a need to go down ...
3k views

### How do I get parabolic movement in Unity using Rigidbody2d?

EDIT: It was the Animator after all. Apply Root Motion basically nullifies any physics based work. I "know" this answer but I can't figure out what can possibly be wrong. My code is in FixedUpdate(). ...
917 views

### How should I implement basic spaceship physics?

I am new to 2D game development. I've made several games, but they've made almost no use of physics. Now I want to try making a game that uses some basic physics to look more realistic. The game ...
31 views

### Steer a flock towards a target? Like in pikmin? [duplicate]

Can a flock be steered towards a target ? I've seen that flocking behavior has the alignement behavior, but can it be directed and steered toward a goal ? http://www.youtube.com/watch?feature=...
159 views

### How do I calculate the motion of 2 massive bodies in space?

I'm writing code simulating the 2-dimensional motion of two massive bodies with gravitational fields. The bodies' masses are known and I have a gravitational force equation. I know from that force I ...
49 views

### What does it mean to cross a scalar with a vector in a 2D plane?

At the moment, I'm following this page to create a physics engine. As per that page, I need to cross angular velocity by a distance vector to get relative torque and such, but I'm not sure how (in a ...
854 views

### Physics engine deltaTime and force acceleration

I am working on a physics engine that uses basic Euler integration to compute forces. So, here is the thing: function applyForce (rigidbody, force) { rigidbody.forces.add(force); } function ...
706 views

### Use both AddForceAtPoint and change velocity property?

I'm using Rigidbody2D for some game objects. It seems that when I AddForce() or AddForceAtPoint(), the game objects are mostly affected on the Y axis and hardly at all on the x axis. I don't ...
185 views

### How can I compute the movement of an object along a parabola?

I am working on a simple 2D game. In the game, I have a 'robot' that throws a ball towards another robot, in the shape of a parabola. Both 'robots' have the same Y coordinate. The program knows the ...
2k views

### OBB Collision Resolution: Jittering with Long Rectangles

I have been working on a physics simulation module. Almost everything works properly, but I am having an issue, which I have demonstrated in the following video. http://youtu.be/2L17y9Lme0Q As you ...