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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195
votes
10answers
55k views

When should I use a fixed or variable time step?

Should a game loop be based on fixed or variable time steps? Is one always superior, or does the right choice vary by game? Variable time step Physics updates are passed a "time elapsed since last ...
66
votes
5answers
31k views

Good 2D Platformer Physics [closed]

I have a basic character controller set up for a 2D platformer with Box2D, and I'm starting to tweak it to try to make it feel good. Physics engines have a lot of knobs to tweak, and it's not clear to ...
48
votes
7answers
6k views

2D Platformer AABB collision problems

I have a problem with AABB collision resolution. I resolve AABB intersection by resolving the X axis first, then the Y axis. This is done to prevent this bug: http://i.stack.imgur.com/NLg4j.png ...
47
votes
3answers
12k views

2D water with dynamic waves

New Super Mario Bros has really cool 2D water that I'd like to learn how to create. Here's a video showing it. When something hits the water, it creates a wave. There are also constant "background" ...
43
votes
3answers
1k views

How to determine which thrusters to turn on to rotate the ship?

The configuration of the ship changes dynamically, so I have to determine which thruster to turn on when I want to rotate the ship clockwise or counter clockwise. The thrusters are always axis aligned ...
36
votes
6answers
7k views

Analysis of Mario game Physics [closed]

I know there's a breakdown of Sonic the Hedgehog physics found here, and I was wondering, does there exist a breakdown of any of the Mario games? Something similar to this but for Mario is what I'm ...
35
votes
3answers
8k views

Why do we use the Pythagorean theorem in game physics?

I've recently learned that we use Pythagorean theorem a lot in our physics calculations and I'm afraid I don't really get the point. Here's an example from a book to make sure an object doesn't ...
35
votes
4answers
2k views

Movement prediction for non-shooters

I'm working on an isometric 2D game with moderate-scale multiplayer, approximately 20-30 players connected at once to a persistent server. I've had some difficulty getting a good movement prediction ...
34
votes
2answers
6k views

Water/Ocean simulation and physics

I'm looking for some references about water simulation, and how to model it's interaction with bodies (like boats, ships, submarines). I've found a lot of references on the visual aspects of water ...
30
votes
6answers
5k views

Implementing a wrapping wire (like the Worms Ninja Rope) in a 2D physics engine

I've been trying out some rope-physics recently, and I've found that the "standard" solution - making a rope from a series of objects strung together with springs or joints - is unsatisfying. ...
30
votes
2answers
2k views

How'd they do it: Destructible environments in BF:BC2 and BF3

How did the folks at Dice create the destructible environments in the more recent Battlefield games? Did they just assemble the buildings out of predefined sub-regions that break apart when there is ...
29
votes
6answers
9k views

About floating point precision and why do we still use it

Floating point has always been troublesome for precision on large worlds. This article explains behind-the-scenes and offers the obvious alternative - fixed point numbers. Some facts are really ...
27
votes
11answers
6k views

Do 2D games have a future? [closed]

I'm currently working on a 2D soft-body physics engine (since none exist right now -_-), but I'm worried that there's no point to spending what will most likely be years on it. Although I love ...
26
votes
2answers
2k views

Calculating the rotational force of a 2D sprite

I am wondering if someone has an elegant way of calculating the following scenario. I have an object of (n) number of squares, random shapes, but we will pretend they are all rectangles. We are ...
26
votes
2answers
3k 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 ...
26
votes
5answers
3k views

Simulating pressure in a grid based liquid simulation

I have a 2D grid based water system in my XNA game, we have a method using cellular automata to simulate water falling and spreading. Example of water flowing down a slope: Each tile can contain a ...
25
votes
5answers
8k views

Lag compensation with networked 2D games

I want to make a 2D game that is basically a physics driven sandbox / activity game. There is something I really do not understand though. From research, it seems like updates from the server should ...
23
votes
7answers
2k views

Multithreading 2D gravity calculations

I'm building a space exploration game and I've currently started working on gravity ( In C# with XNA). The gravity still needs tweaking, but before I can do that, I need to address some performance ...
23
votes
4answers
2k views

What is the point of “delta” in this code? Does it reflect a standard thing in game dev?

I know very little about game programming but would like to learn more. I am trying to understand the code for this game. I am trying to understand why the code is passing a "delta" to ...
23
votes
2answers
19k views

How to make a character jump?

I am currently making a game in C# using Direct X 9.0. The game remake is Donkey Kong NES. I have nearly everything completed, but I am having problems with the physics of Mario's jump. I have ...
22
votes
4answers
2k views

Momentum and order of update problems in my physics engine

This question is a "follow-up" question from my previous one, regarding collision detection and resolution, which you can find here. If you don't want to read the previous question, here's a ...
22
votes
3answers
3k views

Pros and cons of different integrators [closed]

When creating things like physics in games you need an integrator. I've seen Verlet integration mentioned several places as a great alternative to Euler integration. For instance in the famous ...
22
votes
6answers
2k views

How can I Intercept object with a circular motion

I am creating a 2d space game and need to make the spaceship intercept a planet. I have working code for straight line intercepts but cannot figure out how to calculate the planets location in a ...
21
votes
5answers
25k views

How can I implement gravity?

How can I implement gravity? Not for a particular language, just pseudocode...
21
votes
7answers
3k views

Optimizing gravity calculations

I've got a bunch of objects of varying size and velocity which gravitate towards each other. On every update, I have to go over every object and add up the forces due to gravity of every other object. ...
21
votes
2answers
1k views

Correctly Implementing a “Double Jump”

I'm working on a 2D iPhone game using Corona (Trial version, so I can't use their forums). The game involves the character falling through the sky, and I'm trying to implement a "double jump" for the ...
20
votes
3answers
2k views

How does one avoid the “staircase effect” in pixel art motion?

I am rendering sprites at exact pixel coordinates to avoid the blurring effect caused by antialiasing (the sprites are pixel-art and would look awful if filtered). However, since the movement of the ...
20
votes
4answers
4k views

How to deal with corner collisions in 2D?

I'm writing a top down 2d XNA game. Since its my first I'm trying to write the physics and collision stuff myself to learn it. Whenever my player sprite character attempts to move into a position ...
19
votes
4answers
7k views

Is there a 2d physics engine that can model fluids and gases? [closed]

At this point the platform and programming language don't matter I would just like to know if something out there exists for this. Any help is appreciated.
19
votes
6answers
1k views

Data structures for interpolation and threading?

I've been dealing with some frame-rate jittering issues with my game lately, and it seems that the best solution would be the one suggested by Glenn Fiedler (Gaffer on Games) in the classic Fix Your ...
18
votes
6answers
2k views

AI control for a ship with physics model

I am looking for ideas how to implement following in 2D space. Unfortunately I don't know much about AI/path finding/autonomous control yet. Let's say this ship can move freely but it has mass and ...
17
votes
6answers
10k views

How do I build a 2D physics engine? [closed]

The most advanced games I've made are a 8-ball pool game made with the physics engine Box2dFlashAS3 and a platform game with levels. When I did platform games, I've always wished to know how to make ...
17
votes
2answers
4k views

How are physics or graphics components typically built in a component-oriented system?

I have spent the last 48 hours reading up on Object Component systems, and feel I am ready enough to start implementing it. I got the base Object and Component classes created, but now that I need to ...
17
votes
1answer
8k views

Quad tree vs Grid based collision detection

I'm making a 4 player co-op r-type game, and I'm about to implement the collision detection code. I've read a lot of articles and stuff about how to handle collision detection, but I'm having a hard ...
17
votes
1answer
3k views

Ideas for 2D Water Simulation

I am looking for any input on simulating water in 2D, against a rather large (call it) blocked/not blocked array (viewed from the side). I have come up with the following ideas: Cell Automata Do a ...
16
votes
2answers
5k views

Why is RK4 better than Euler integration?

At the end of these great slides, the author compares all the different integrators presented. One way or another, they all fall short except for Improved Euler Integration and Runge Kutta 4 ...
16
votes
1answer
727 views

Recreating retro/NES style physics with intentional imprecision

Background: I'm having a problem getting the jump curve correct for a retro platformer remake project of mine. The original game is for the NES, and the player's velocity is stored in two separate ...
16
votes
3answers
8k views

What is a good book on physics for game development?

I'm looking for a good beginners' book on the subject of physics in game development. Something that focuses on 2D games would be preferable.
15
votes
7answers
24k views

In Pong, how do you calculate the ball's direction when it bounces off the paddle?

I'm trying to wrap my head around this very Hello World-y problem in game development. I've created a TicTacToe game in XNA so I guess the next step would be a Breakout clone. Keep in mind that I ...
15
votes
3answers
615 views

Solids as high viscocity Liquids

A friend of mine and I were discussing different idea for allow materials in a world to be destroyed in a very piecemeal fashion and he proposed the idea of representing solids as very viscious ...
14
votes
3answers
3k views

How do I handle moving platforms in a platform game?

I don't want to use box2d or anything, I just want simple moving platforms (up-down, left-right, diagonal and circular paths). My question is to handle the update order / control hierarchy so that the ...
14
votes
3answers
3k views

How can I create a stretchy, breakable pizza cheese material?

I want to create realistic pizza and allow user interact with it. What I want: What I created: I created model of the pizza (8 pieces) in Blender, then imported it into Unity. The piece of ...
14
votes
2answers
6k views

2D Planet Gravity

I'm trying to make a simple game where a spaceship is launched and then its path is effected by the gravity of planets. Similar to this game: http://sciencenetlinks.com/interactives/gravity.html I ...
14
votes
1answer
2k views

Any fixed-point portable open-source 3D physics engines?

I'm looking for a fixed-point 3D physics engine (basic kynematics and collision detection-resolution... nothing too fancy.) I need fixed-point math because I'd like to have deterministic results, for ...
13
votes
3answers
3k views

Resolving a collision with forces

In my 2D physics engine, I can detect AABB vs AABB collisions, and resolve them by finding the shortest penetration vector and adding it to the AABB's position. Doing this "pushes" the first AABB ...
13
votes
2answers
4k views

In a 2D platform game, how to ensure the player moves smoothly over sloping ground?

I'm developing a physics engine for a 2D platform game. I'm using the separating axis theorem for collision detection. The ground surface is constructed from oriented bounding boxes, with the player ...
13
votes
5answers
1k views

How could you parallelise a 2D boids simulation

How could you program a 2D boids simulation in such a way that it could use processing power from different sources (clusters, gpu). In the above example, the non-coloured particles move around ...
13
votes
2answers
1k views

Resources of realistic water simulation?

I want to study water simulation, with a a demo with source code which using physically-based methods(Eulerian approaches or Lagrangian approaches). How can I get some examples?
13
votes
3answers
2k views

Powder games: how do they work?

I recently found these two gems: http://powdertoy.co.uk/ http://dan-ball.jp/en/javagame/dust/ My question is: How are the physics with so many elements efficiently handled? Am I just severely ...
12
votes
3answers
4k views

2D game collision response: SAT & minimum displacement along a given axis?

I'm trying to implement a collision system in a 2D game I'm making. The separating axis theorem (as described by metanet's collision tutorial) seems like an efficient and robust way of handling ...