• 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
Norman Barrows

"fix your timestep" question

6 posts in this topic

with respect to the following article:

 

http://gafferongames.com/game-physics/fix-your-timestep/

 

 

at the end, where he's interpolating values based on fractions of a time step left over,

 

am i to understand it that for example, the physics simulation is on time step 4.5, and he uses that .5 left over to interpolate between time steps 3 and 4, to come up with values for timestep 3.5, then draws the interpolated state of the simulation at time step 3.5 when the simulation is _actually_ at timestep 4.5? IE drawing based on an estimated past state, not the true current state of the simulation? And always draws ~1 frame behind whats actually going on?

 

i take it that the physics engine and render engine running slightly out of phase temporally (~1 frame) has no major impact on gameplay? 

 

and without interpolation, you get the temporal aliasing of the occasional 2 steps per frame when the accumulator rolls over?

 

and interpolation is really only required for deterministic games ?

0

Share this post


Link to post
Share on other sites
No, I don't think that's what the article is saying (although I haven't read it in a long time and I am not re-reading it to answer your question). The reasonable thing to do at time 4.5 is run the simulation up to step 5, and then interpolating between steps 4 and 5. Notice that it's OK to compute the state at time 5 now, because it can only be affected by inputs available at time 4, which we have.
2

Share this post


Link to post
Share on other sites


Notice that it's OK to compute the state at time 5 now, because it can only be affected by inputs available at time 4, which we have.

 

tricky!  ; )

 

so interpolating between current and next isn't a problem, as next is based on current's input. this does assume a certain order to input, render, and update though, doesn't it? 

 

in the end, they're endless loops, so the particular order doesn't always matter, or two orders may be functionally similar, but not both start at the beginning of the game loop. 

 

render, input , update is simply an out of phase version of input.update,render, that starts with render instead of input on the first iteration. once the loop is running, there's no real difference. only perhaps as far as which "step", "turn" or "frame number" you say something is on.

 

i use the render, input, update ordering. so there, one might say i render step 4, then get input for and compute step 5. on the next game loop iteration, i draw step 5, and get input for and compute step 6.

 

from this description you can probably tell i take a very different approach to the main game loop as far as coupling / decoupling the input, update, and render parts of the code. thus my interest in the topic. 

0

Share this post


Link to post
Share on other sites


You forgot the most important reason, and that is choppy framerate.

 

So its really all about smooth high speed animation then? run update() at 30 fps, and let render() scream at full throttle, and just interpolate between frames, like animation tweening, eh?

0

Share this post


Link to post
Share on other sites

 


You forgot the most important reason, and that is choppy framerate.

 

So its really all about smooth high speed animation then? run update() at 30 fps, and let render() scream at full throttle, and just interpolate between frames, like animation tweening, eh?

 

 

yes, interpolation is nice...

 

note that interpolation (and also extrapolation) may also be relevant in network games, partly as the server may send out delta-frames at a relatively slow rate, and also ping-times may be potentially significant. so, it may be necessary to extrapolate ("guess") where things are at the current time, rather than exactly where the server said they were, ...

0

Share this post


Link to post
Share on other sites


note that interpolation (and also extrapolation) may also be relevant in network games, partly as the server may send out delta-frames at a relatively slow rate, and also ping-times may be potentially significant. so, it may be necessary to extrapolate ("guess") where things are at the current time, rather than exactly where the server said they were, ...

 

as a hard core flight sim fan, the mere mention of simulation inaccuracies like lag and prediction makes my skin crawl! <g>. i want to simulate, not play a mere game.

 

however i do realize they are a necessary evil required for networked titles.

 

i've only added multiplayer to one of my games ever. it was a flight sim, and ran in lockstep. the protocall was proprietary, and so robust that you could unplug the phone line and not lose sync. however it was not 100% bulletproof. i don't think any protocall can be. you can only ACK ,ACK's so many times. eventually you have to take it on faith that the last  "i got your ack" goes through

 

.

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