Game Physics
Hi, I’m Glenn Fiedler and welcome to my series of articles on game physics.
In this series you’ll find information about RK4 integration, the best way to time-step your simulation, rigid body simulation in 3D, spring physics and how to network a physics simulation.
If you find these articles useful, please consider making a small donation to support my writing and help cover hosting costs. Every few years I take time off between game projects to write these articles for you, and that means I don’t get paid to do it!
Thanks!
Glenn Fiedler
gaffer@gaffer.org
Integration is used to determine the motion of an object over time. In this article I show how to correctly integrate the equations of motion using an RK4 integrator instead of starting off on the wrong foot with a stupid Euler integrator.
Even an RK4 integrator is sensitive to the amount of time you step when integrating. Decouple your physics timestep from the display framerate so that your simulation behaves exactly the same way each time it is run.
Leap ahead from integrating single values to integrating the entire physics state for a cube in three dimensions. Introduces rotational physics concepts including orientation in 3D, angular velocity and momentum, inertia and torque.
Explains the physics of springs and how to apply them to control physics simulations. Learn how to implement joints, constraints, motors and basic collision response.
How do network games synchronize physics over the network? This article explains the core techniques used in today’s first person shooters and shows how you can apply these techniques to network your own physics simulations.
This articles are insightful. Very recommended.
These articles have been extremely helpful. Thank you very much!
These articles are very useful but I can’t find any way to navigate to them from your homepage, none of the links lead to these.
Fixed!
Hello Glenn,
Greetings on that series of articles.
Any idea how to integrate Coulomb contact friction in
particle – mesh or particle – particle interaction?
hey mikhail, i don’t know how to do that yet – sorry!
Great articles. Really helped me out. I find that alot of the documentation for this kind of material is generally written in a style suited to mathematicians which I find difficult to interpret. Thanks!
yeah you and me both, its like they actively try to make it hard to read
Hey glenn I was wondering, do you know a lot of calculus ? Do you study daily ? I’ve seen most people pick the formulas and general algorithms to make their physics but they usually don’t know what exactly the formulas mean.
i’m a self taught programmer, i have no degree but i’ve gone to a few university courses to brush up on some more mathematics – and i did advanced math in highschool, so i have decent background, but really *nothing* on somebody who went through actual physics or electrical engineering maths
in otherwords, i have “programmer mathematics”, meaning i learn what i need to do what i want to do, and not much more
so i don’t do calculus daily, just when i need it. and usually, it’s very VERY slow
but a key thing is that i always try to understand, as deep as i can what i am working on… so I do know the taylor’s theorem basis for RK4 and understand it, and i can derive it if necessary. the only thing i’m a bit fuzzy on in the whole physics articles is how to calculate the spin quaternion to integrate the orientation from angular velocity. i don’t fully understand the mathematics behind that, but the rest i’m pretty solid on.
if you want to study something to get a deeper meaning of the physics equations, i highly recommend taking a look at baraff’s siggraph courses on physics simulation (google for it) – this is a good place to get a good understanding of the mathematics and ideas behind physics simulation
in fact really, you could just look at my articles as a poor man’s version of his papers, covering much the same material, but with a programmer focus instead of a mathematics focus
cheers