• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
vadevaman

Timesteps and "timesteps"

8 posts in this topic

Does anyone know a way to "hack" a different timestep under the current timestep?
I know It doesnt seem logical at first, but I remember something done with looping in a fixed update. And then basically damping the resulting values with variables found in the loop. I dont remember how its actually done, but does anyone know the name of this method and can guide me how to use this?

The main reason I ask this is because I have a simulation running at 50hz (1/0.02)
But id like to run some calculations in 1000hz (1/0.001)

 

Basically I'm simulating car physics, the driveline calculations work well at 50hz, but tires not so well. They get really jerky at low speeds, it seems to be the hardest topic in car simulations.

Anyway I'd like to run slipAngle and slipRatio calculation at 1000hz. I found that SAE methods work pretty well at 1000hz, not perfectly, but  good enough to keep the car 100% static at full stop.

 

Or if I dont need a different timestep, then could anyone give me some pointers on how to damp the slip calculations at low speeds? Switching to a velocity based friction model didnt give any good results. I had some notable side effects.

Also as a side topic cold anyone simply explain how's Runge-Kutta working and is it any good or it's out dated?

Thanks!

0

Share this post


Link to post
Share on other sites

I am not familiar with the challenges of writing car physics, but I would try to find a more stable integrator.

 

What is "SAE"?

0

Share this post


Link to post
Share on other sites

Is your time integration explicit? If so, you may want to try an implicit method. Though implicit is more computationally expensive, you can get away with much larger time steps, so in practice it tends to be faster. The downside is its more complicated to implement.

 

Runga-Kutta is fine, you can do it implicit or explicit. It is still widely used in computer modelling. The wiki page on RK is pretty good.

0

Share this post


Link to post
Share on other sites

Drop the Runge Kutta 4th order integration method! Yes, it does an excellent job at preserving energy, and no, it's not very good for game physics. Instead, use the symplectic Euler 1st order or Verlet 2nd order. Alternatively, use impulses instead of forces and drop the integrator completely, which gives the same result as symplectic Euler.

 

Cheers,

Mike

0

Share this post


Link to post
Share on other sites

A simple approach that I've used in my games is:


lagTime = 0;

while (isActive)
{
   frameTime = getFrameTime
   lagTime += frameTime;
   dt = constant frame rate;
   while (lagTime >= dt)
   { 
     integrate(dt);
     lagTime -= dt;
   }
}
0

Share this post


Link to post
Share on other sites

I should just point out to anyone reading this, Runga-Kutta is a family of methods. RK4 or, 4th order Runga-Kutta, is very common but just one method in the family. As other posters have implied, 4th order accuracy is overkill for a game. But that doesn't necessarily rule out the whole family of methods.

0

Share this post


Link to post
Share on other sites

I should just point out to anyone reading this, Runga-Kutta is a family of methods. RK4 or, 4th order Runga-Kutta, is very common but just one method in the family. As other posters have implied, 4th order accuracy is overkill for a game. But that doesn't necessarily rule out the whole family of methods.

 

Correct, it's a family of methods, not a single one. Should be mentioned. But my opinion is similar with the other members. I have implemented 2nd and 3rd order RK just once and never used them again, since they either introduced or removed a lot of energy from the system and generally did a poor job.

 

A few years back I tested a lot of integrators in the hopes that they would improve my simulations greatly above the standards of symplectic Euler. Well, I was mostly disappointed. The only two exceptions are the 2nd order velocity-less Verlet and the family of higher order integrators by David Whysong. These are just awesome, and I use them mainly for high accuracy space physics. If you want energy preservation, these 4th, 6th, and 8th order integrators will definitely do the job:

 

http://www.projectpluto.com/symp.cpp

 

Cheers,

Mike

Edited by h4tt3n
0

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0