in case you've been using some implementation of simulation stepping function based on, or similar to what is described in this article:
GafferOnGames: "Fix Your Timestep!"
..then, you might be interested in 2nd opinion on these matters,
actually, after completing intensive research there was a realization that it turns out almost "everyone" is using some version of this algorithm with interpolation, including popular Physics engines, libraries and commercial console and PC games
..anyway, there is "a paper" on this,
and some 'bonus material' that actually turns this tech. paper into an Allegory Novella and couple of more other things.. how wonderful!
TITLE: Three Bugs With One Stone ..allegory continues
(RealTime Allegory Novel, Technical Paper and Chronological account of an Algorithm discovery)
..there you can find some bits of discussion related to these issues, but not present on the internet anymore, like this for example: Quote:
-"ok, cazy i'll prove it via logic, just because i'm feeling a bit evil now.."
//------------------------------------------------------------
Aug 30, 2008
>>"This code handles both undersampling and oversampling correctly which very is important. "
- not really,
unless somehow you can make your physics calculations in zero amount of time.. but, you seem to know that and call it "spiral of death"
..i'm just saying you should remove word "undersampling" from the same sentence with word "correctly"
//------------------------------------------------------------
Aug 30, 2008
>>"..but at least its theoretically correct"
- not really,
unless there truly is such thing as "correct theory" that does not work in practice
>>"..i shipped this technique in 'freedom force' from irrational games.."
- then it is an example how it does not work - scrolling speed goes from fast at the edges of the map to slow and jerky depending on the scene complexity and number of moving objects
not that it matters much as i see the game scored 'Outstanding 9.3' on IGN, congratulations!
cheers
//------------------------------------------------------------
Sep 3, 2008
>>"plus i don't see where you are interpolating render state between two sim states -
* are you doing that?
* do you understand why we need to do that?
* do you understand what temporal aliasing is and why we need to do the interpolation?"
- no, im not doing that,
..actually more i look at it - more it feels "out of the place"
>>"your technique is not identical to mine.. this violates the desired constraint of this article, that you are always stepping forward with a fixed dt"
- well, call me crazy,
but that interpolation you're talking about seem to goes against all the desired constraints of your article - it actually changes the "state" outside of fixed time steps, no?
//------------------------------------------------------------ |
Chapters:
I) Genesis, anecdote
II) Divina Commedia, abysm spirale
III) Seraphim snd Nephilim, the chronicles
IV) Aspidochelone, physiologus
V) ..alegoria continua
..among other themes,
book most obviously and most practically addresses these issues:
Quote:
---------------------------------------------------------------------
Common bugs in Havok, PhysX, Bullet, ODE, Ogre, Newton.. SOLVED!
Bug 1.) Few subSteps: "Moon gravity effects"
bUg 2.) A lot of subSteps: "Spiraling to death"
buG 3.) Interpolation VS. Temporal Distribution
Common mistakes and bugs related to fixedTimeStepping - UNCOVERED
4.) Design-Time Planning and Recognition of Hardware Min. Sys. Requirements
5.) "Scaling the World": Gravity, Mass, Size and Hidden Effects of fixedTimeStepping
6.) Jitter, Wobbles, Choppiness and Slowdowns: Unstable Physics & Smooth Animation
---------------------------------------------------------------------
Quick Overview: www.geocities.com/ze_aks/test/sampleTest.html
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[Edited by - Ravuya on October 1, 2008 12:26:50 AM]
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Posted - 10/1/2008 12:43:16 AM
Posted - 10/1/2008 1:22:51 AM
