-"Eris in Greek mythology,
the Greek goddess of discord, quarrel, strife and conflict. Sometimes equated with the war goddess Enyo, her name translates into Latin as Discordia. The solar system's largest known dwarf planet, is named after this goddess.

So, after all, there was not one kind of Strife alone, but all over the earth there are two. As for the one, a man would praise her when he came to understand her; but the other is blameworthy: and they are wholly different in nature. For one fosters evil war and battle, being cruel: her no man loves; but perforce, through the will of the deathless gods, men pay harsh Strife her honour due.

But the other is the elder daughter of dark Night (Nyx), and the son of Cronus who sits above and dwells in the aether, set her in the roots of the earth: and she is far kinder to men. She stirs up even the shiftless to toil; for a man grows eager to work when he considers his neighbour, a rich man who hastens to plough and plant and put his house in good order; and neighbour vies with his neighbour as he hurries after wealth. This Strife is wholesome for men. And potter is angry with potter, and craftsman with craftsman, and beggar is jealous of beggar, and minstrel of minstrel.

The most famous tale of Eris recounts her initiating the Trojan War.
The goddesses Hera, Athena and Aphrodite had been invited along with the rest of Olympus to the forced wedding of Peleus and Thetis, who would become the parents of Achilles, but Eris had been snubbed because of her troublemaking inclinations.

She therefore, in a fragment from the Kypria as part of a plan hatched by Zeus and Themis, tossed into the party the Apple of Discord, a golden apple inscribed - "Kallisti" (To the Fairest One) - provoking the goddesses to begin quarreling about the appropriate recipient.

The hapless Paris, Prince of Troy, was appointed to select the most beautiful by Zeus. Each of the three goddesses immediately attempted to bribe Paris to choose her. Hera offered political power; Athena promised skill in battle; and Aphrodite tempted him with the most beautiful woman in the world: Helen, wife of Menelaus of Sparta. While Greek culture placed a greater emphasis on prowess and power, Paris chose to award the apple to Aphrodite, thereby dooming his city, which was destroyed in the war that ensued."

-"Harmonia in Greek mythology,
the immortal goddess of harmony and concord, corresponding to the Roman goddess Concordia, daughter of Ares and Aphrodite (War & Love), rationalized as closely allied to Aphrodite Pandemos - the love that unites all people, the personification of order and civic unity.

Harmonia is renowned in ancient story chiefly on account of the fatal neck­lace she received on her wedding day. The necklace had wrought mischief to all who had been in pos­session of it, and it continues to do so.."

Stepping the simulation correctly - living la vida loca
(Intel Software Network, Havok Physics Engine Public Forum)

September 7, 2008
but really,
we have situation like this..

[MISSING-REPEAT]

although obvious,
this may pass unnoticed - "undersampling" is theoretically and practically only possible if the time to execute one simulation step is smaller than the fixed time step being simulated ..in a real-time that is

simDT < fixedTimeStep <-- !!!

"Half-solution A"
..here's 2nd scenario and one of the ways to avoid spiraling singularity by treating it as a 'special case' ..it is actually your old algorithm until simDT >= STEP at which point we have no choice but to slow down the simulation speed if we insist to stay with the same fixed time step - the difference is that this implementation will not spiral "down to death" and no capping will occur which should result in smoother animation and still preserve accuracy and determinism... furthermore, this little addition will try to compromise between keeping high FPS and high as possible simulation frequency depending on fpsTensor variable..
//---------------------------------------------------------------------
while( theBeatGoesOn )
{
nowTime= getCurrentTime(RTN_SECONDS);
accum+= deltaTime= nowTime - lastTime;
anmDT= deltaTime - simDT;
if(cnt>0) simDT/= cnt; lastTime= nowTime; cnt= 0;
while( accum >= STEP )
{
stepSimulation( STEP ); cnt++;
accum-= (simDT >= STEP)? simDT+(STEP*anmDT*fpsTensor) : STEP;
}
simDT= getCurrentTime(RTN_SECONDS) - lastTime;
renderScene();
}
//---------------------------------------------------------------------
(R) All rights reserved, don't you dare use this code unless you can prove to me you're human being.
Use of this algorithm in commercial products without my permission will be cheerfully taken to court.

September 7, 2008
(Re)Designing an API...

>>"Thus newbie code.. / ..more newbie-friendly / ..so that newbies have an easy time / ..also be newbie-friendly / easy for newbies.. / The newbie developer.. / what newbies pass.. / really help the most to the newbie end user"

- how in the world.. newbies?
there is no such thing really.. that logic is artificial and when forced to existence can make you only do the wrong things.. you SHOULD NOT design *anything* for newbies, never, ever... the closest thing to that misthink is a designing 'graphical user interface' for children or handicapped... no TVs for newbies, no remote controller for newbies, no Xbox for newbies, no C++ for newbies..

because in practice it means - trying to accommodate for someones ignorance, assumptions and every other way people can be foolish... plenty of those, futile attempt obviously, eh?

look,
you dont really have to think about API and "interface" at all, not as such - make your code SMALLER, not necessarily in the number of characters or even lines of code but smaller in the number of *terms* you define to communicate information and response throughout the program.. of course it does almost always practically lead to less lines of code, less variables, less function calls, less arguments.. less of everything

and by doing so,
you would most certainly make it faster and more memory efficient as well - but the best of all, simplicity and bare logic is all you need to accommodate newbies - it will be *easy to learn*

"All other things being equal, the simplest solution is the best."
-Occam's razor

September 7, 2008
hi,

sorry i wasn't really replying directly to you.. this could answer.. let me copy/paste...
- it is a DESIGN TIME DECISION, this means that you must be aware of how much time it takes CPU to execute stepSimulation() when designing an application and as same as you have little FPS counter at the design-time, so you should have "simDT" and if that number ever gets to "red" (close to fixedStep) you try to design with larger fixedStep or you try to optimize, basically im saying - its the CPU that is critical for determining and deciding on min. sys. requirements becuse of (simDT * N) ..GPU scales much better, smoother

..in any case, in the design time,
you want to go for the largest possible fixedTimeStep you can get by (lowest frequenct eg. 10Hz) just so you can support that lower class CPU or you have more time to render..

[MISSING-REPEAT]

September 7, 2008
oh, sheesh!

im sorry.. i was stupid enough not to read much of what was going on before in the thread except to notice the confusion..

let make it clear,
in no way i was talking to you or anyone, it was all copy/paste just because its related topic..

cheerio

September 7, 2008
could you implement the algorithm i gave and make the graphs with same computers and same application so we can compare, please?

i promise it will be smooth/smoother ..thank you!

btw,
did you manage to extract "your" answer from all the stuff above?

September 7, 2008
change this:
--------------------------------------------
// time accumulator
static float elapsed = 0.0f;
elapsed += timeSinceLastFrame;
// update using time slicer
while( elapsed > m_timestep )
{
m_world->stepDeltaTime( m_timestep );
vdb->step( m_timestep );
updateDisplay( m_world );
elapsed -= m_timestep;
m_physicsStepsLastFrame++;
}
--------------------------------------------

to this:
--------------------------------------------
m_physicsStepsLastFrame= 0;
static float elapsed = 0.0f;
elapsed += timeSinceLastFrame;
while( elapsed >= m_timestep ) //<--- ..or equal
{
m_world->stepDeltaTime( m_timestep );
vdb->step( m_timestep );
elapsed -= m_timestep;
m_physicsStepsLastFrame++;
}
updateDisplay( m_world ); //<--- out of the loop
--------------------------------------------

..and you'll probably be fine as it is, if not try smaller "m_timestep" ..i suppose its const. value something like 0.0166 so try LARGER STEPS like 0.033

but even better,
give me an equivalent of - getCurrentTime(RTN_SECONDS)

and i'll make you even better loop,
but then you make those graphs for me, how's that?

now i dont know a thing about Havok,
but something tells me you dont want to be using this "approxTransformAt()" ..just a wild, wild guess

September 7, 2008
there is no need to talk about anything else but those few lines of code we already have there, all we need to talk about is how to modify it slightly.. forget everything for a second, especially "approxTransformAt()" for now at least

..then, when we modify your loop and make it perform different algorithms, i would like you to take the screenshots of those graphs, i actually need you to do that because only you have your computers and Havok installed i only have my computers and i dont have Havok at all..

can you do that?

September 8, 2008
have you noticed that i uncovered the bug in Havok design and presented solution?
its only natural that after much time and effort i would like to get some feedback on that?

should i post it in bug-reports or contact someone else in regards to this?

thank you

September 8, 2008
hi,

does Havok implement stepping with "maxSubSteps"?

if so than it is a wrong implementation,
that causes visual bug knowns as "Moon-gravity effect" and it poorly handles the case when physics symulation becoms a bottleneck... should i post in bug-reports?

thank you

September 9, 2008
well, in any case this will work better - whether is implemented inside the library or in the main program loop, so here is the "full-solution A" implemented with Bullet library..

//------------------------------------------------------
int btDiscreteDynamicsWorld::stepSimulation( btScalar timeStep,int maxSubSteps, btScalar fixedTimeStep)
{
m_localTime+= (timeStep < fixedTimeStep*2)? timeStep : fixedTimeStep*2;
saveKinematicState(fixedTimeStep); applyGravity(); maxSubSteps= 0;
while( m_localTime >= fixedTimeStep )
{
internalSingleStepSimulation(fixedTimeStep);
m_localTime-= fixedTimeStep; maxSubSteps++;
}
synchronizeMotionStates(); clearForces();
return maxSubSteps;
}
//------------------------------------------------------

again,
there is no need to change anything anywhere else

..solution B is simply about switching switching fixedTimeStep to some larger value, which might suit some cases better, but the one above is probably more general and give desired visual effect considering circumstances

September 9, 2008
>>"I'd really rather not continue to discuss this further unless you're having an issue using Havok. "

- it is an issue with real-time simulation/animation and therefore is issue with Havok too and in the same time explanation why i dont really need to know a thing about Havok at all..

so, i wish to help other people to solve the issue too, is public forum not the place to discuss and the place where people help each other?

i dont have any issue because i know the solution,
and i have come here to tell you about it, to help you... but you're not required to be a part of discussion, if this is a public forum let public to discuss and say for themselves.. your lack of understanding is not a reason for keeping others to do so

>>"Havok.. The solver is iterative and you can tweak the number of iterations it takes but that's different to substepping a simulation."

- really?
and by "tweak" do you not mean - "set a Maximum number of substeps/iterations"?

>>"The code outlined above is also confusing as you pass maxSubSteps in by value but then ignore whatever value is passed in."

-exactly!!
and it works! ..do you get it?

>>"I'm just being careful here for people reading this thread and seeing you stating that the code above works in all cases as that's misleading."

- this whole thread was misleading because you confirmed the code given was good, when in fact had TWO unbelievably huge errors

now if i did nothing else but fix that, as i did.. surely there should be a little appreciation for that, not to mention that the rest i said is much more helpful and useful, but even if you do not agree ..why so angry?

can i talk to you manager?
your ignorance is seriously getting in the way of PUBLIC BENEFIT, your attitude towards someone who is offering help is very strange ..your emotions should not be a vehicle to CONTROL THE INFORMATION ..let the people have it!

cheerio

September 14, 2008
..surely this is in everyones interest and someone could at least confirm am i right or wrong?

i can only test it as much, and i ask everyone for help,
hope thats not too much to ask.. after all, if it works then we all benefit, right?

thank you

September 16, 2008
in case you were wondering,
but for some reason never got around to ask

Copyright/Intellectual Property..
- but, do humans need such a thing at all?

algorithms... that should be OURS!!
IP is rubbish, we must SHARE and COMMUNICATE if we want to progress!

..this was my WHOLE POINT with silly copyright notice
(btw, since then i got angry, so - patent pending ;-)

good bye,
rainbows and lollipops

//------------------------------------------------------------------------------
"People, I just want to say, you know, can we all get along? Can we get along? Can we stop making it, making it horrible for the older people and the kids?...It’s just not right. It’s not right. It’s not, it’s not going to change anything. We’ll, we’ll get our justice....Please, we can get along here. We all can get along. I mean, we’re all stuck here for a while. Let’s try to work it out. Let’s try to beat it. Let’s try to beat it. Let’s try to work it out."

September 19, 2008
if you use fixed time steps in your 'game',
whether with your own physics library or Intel Havok, nVidia PhysX, Bullet, ODE...

you are most likely using this algorithm that deals with the maximum number of iterations in the following way:

//-------------------------- *** ORIGINAL algo - capping the NUMBER
cnt= 0;
time= 10;

maxSteps= 5;

while(time > 0 && cnt < maxSteps)
{
step(); cnt++;
time--;
}

//--------------------------
Iterations, cnt= 5
"Time left", time= 5

now, the problem with its practical implementation is in that you have to guess the NUMBER, and it manifests in two ways under certain circumstances:
1.) guess was too low for target CPU - "moon gravity effect"
2.) no matter how high - on some target 'slow enough CPU' it will "spiral to death"

which is not a "real problem",
because you can sort it out in design-time, but the peculiar thing is that it also seem to try to deal with the reminder of the time after the iterations have finished, with -interpolation- , which i think only introduces the errors and its not really necessary?

//--------------------------------------------------------------------------------
+++SOLUTIONS,
this practically solves both problems and removes any errors possibly introduced by interpolation:

//-------------------------- *** 1st algo - scaling the TIME "inside"
cnt= 0;
time= 10;

scaleFactor= 1;

while(time > 0)
{
step(); cnt++;
time--; time-= scaleFactor;
}

//--------------------------
Iterations, cnt= 5
"Time left", time= 0

//-------------------------- *** 2st algo - capping the TIME "outside"
cnt= 0;
time= 10;

if(time > 5) time= 5;

while(time > 0)
{
step(); cnt++;
time--;
}

//--------------------------
Iterations, cnt= 5
"Time left", time= 0

..hope this helps,
but, let me underline that this is not about Physics at all - it is about Graphics, its about Animation, its about FPS.. it is also about Mathematics since it is about an Algorithm ...its not about Physics

* its about the Algorithm that distributes those animation FRAMES per second, in a REAL-TIME

it is a little 'while loop' and only 3-5 lines of code, BUT
- this is the very essence of computer ANIMATION and the core 'function call' of any real-time simulation / game, right?

its not about the Physics,
it may be unfortunate circumstance that it ended up implemented in the Physics libraries, while it really belongs in the main program loop.

there is "a paper" on this and there you can find practical implementation and copy/paste source code to REPLACE your existing algorithm, so this can be easily tested in 5-10 minutes, and the difference is very obvious..

am i right or wrong?

thank you,
gameBoX Linux

September 19, 2008

>>"I guess you want to show me.."

- no, i wanted to do everything for you

in return,
i wanted you to press 'print-screen' button couple of times and post pictures back here

hint:
dont delete previous messages - read them

September 19, 2008
>>"However, we really won't permit rudeness and a lack of respect to other users of the board." - obviously it turns out i have a problem communicating with the most of "the world" ...People are different. Cultures are different, languages are different, moral and ethical norms differ from family to family, form town to town, from country to country and from planet to planet (see Star Trek). English is not my 1st language, i need to use dictionary a lot and i have sense of humor that not many people get, unfortunately. (this also means that it took quite some time to write and try to explain all that) i believe every criticism is constructive as long as you state your reasoning or otherwise show the logic of your conclusion, i even believe you can go as far and say that im stupid as long as you can explain it or at least try to reason your opinion with some arguments - i do not think that i was rude. you will need to quote what i said that you think its rude so i can understand, and improve if it turns out you were right about it for instance, the 1st thing S_W said to me was: -"Hi abaraba, thanks for the lengthy responce." which, to me, sounded like: -"Hi abaraba, but i cant really be bothered to read all thatc" ..and i thought that was rude >>"Please be careful how you address people in the future, if your behavior continues we may have to limit your access to the forum." - i will, and i was ..to the point to still amuse my craziness, but you can go on live your whole life thinking the earth is flat if you like, its not "important" information if you don't care about it, but if you use it in your line of work.. there is just no point in arguing if you are not interested enough to pursue the matter for your own interests but why do we talk about all this - i forgive you! ..now, lets talk about the ALGORITHM

September 20, 2008
>>"I'm sorry if you've been offended by my response abouth the length of your post, this wasn't intended. So here is a video.."
- i dont think you're rude, it just 'came out' that way - maybe lazy a bit ;-)
..but what am i if i dont try to TOLERATE ..i think X-Men movie rather beautifully teach us about that

anyway,
should i go on and submit this here: SIGGRAPH?

but it doesnt seem to be very simple procedure,
- and would anyone go on to submit this without checking it out with general public first?
- i mean, i dont even know if this is some misunderstanding, i dont know if im right or wrong?
- simply, i cant be sure, and i can not go on claiming something if i cant confirm my results and my conclusions, right?

would anyone care to discuss this and actually confirm OR prove it wrong, im happy with either.

cheers

September 20, 2008
i suppose by now some bosses at Intel or Havok are aware of my clames of these bugs, but if not could you please make them aware, and could you please call some Havok engineers that are actually working on this part of the library so they could make some comment?

thanks

September 21, 2008
>>"posting emotional responses on your thoughts about "Newbies""
- but, i did say:
>"let make it clear,
in no way i was talking to you or anyone, it was all copy/paste just because its related topic.. "

..actually, if you care to read,
you can follow the 'second quarter' of how i came about to this "discovery", you can find out how the whole 'newbies thing' came about, and if you follow all of the seven pages of that conversation, you can actually see the exact moment when i snapped at the end.. that was the point where i almost completely gave up from the whole "thing"

Genesis, anecdote
-"Snake! You can't do that!
The future will be changed! ..You'll create a time paradox!!"

now, its a month after that..
and im still trying to "convince" people to even listen to me?

September 21, 2008
would you be any less crazy after that?

hope that explains.. and im sorry, whatever i said it was not to YOU, it was anything but personal, no one can blame you for not being aware that some day some crazy guy would come up crazed like this.. sorry, we both got caught up in the butterfly effect..

so, even if i wasnt crazy, which i was, i would most certainly be by now.. its a simple human mechanism that can protect you from the reality... rainbows and lollipops
(the problem is in turning it off)

cheers

September 21, 2008
have you noticed the part when i say -

>"note,
everyone has source code -its yours-, go on, change everything as you like... i will try your Bullet library for newbies and maybe id stand corrected, dont let me discourage you, its only an opinion.."

c'mon people,
you give me all your algorithms i'll try them all out - because i'm making the best game in the world here, so i need all the KNOWLEDGE i can get!

...what kind of game are you making?

September 21, 2008
let me summarize all those capital words... maybe id seem less crazy

i think every game should be like 'Katamari Damacy' in that its COOL when you have the whole EARTH (and beyond) to play with ..and everything should be destructible, people just love to destruct, its fun.. i suppose..

algorithms are knowledge,
* nothing should stand in the way of the knowledge,
IP in IT is bad, Open Source is good

to gain and keep knowledge there should be peace,
* nothing should stand in the way of the peace,
communicate, share, tolerate..

..have i completely lost it?

September 24, 2008
actually, i found some more of these bugs,
we can talk about these too.. its somewhat related to this, but it has nothing to do with Havok, it just seem to be a common mistake..

by the way,
if you think that some of the stuff i said 'came out' a bit odd, we can talk about that too

September 25, 2008
- "Please,
As I was saying, she stumbled upon a solution whereby nearly 99% of all test subjects accepted the program, as long as they were given a choice, even if they were only aware of the choice at a near unconscious level. While this answer functioned, it was obviously fundamentally flawed, thus creating the otherwise contradictory systemic anomaly, that if left unchecked might threaten the system itself. Ergo those that refused the program, while a minority, if unchecked, would constitute an escalating probability of disaster." (theMatrix.t)
//------------------------------------------------

ahm.. there are two stories here,
one story is 'obvious story', its just what it is - a conversation on public forum where im trying to argue, somewhat emotionally, a validity of this bug-report and propose solution to which i would like to have some feedback on.

now,
the other story is a little sci-fi 'Cyberpunk NOVEL', kind of like the Matrix trilogy, hence the preluding quote, but this tale is all in ALLEGORY, i.e. it has symbolic or figurative meaning and its already told, its woven within this real-time dialog/monologue on public forum, its a "real-time allegory novel" if you will.. i hope you will like it, i think it rather obvious and easy to spot..

- its about "good and evil" (Intel/Havok), about the beginning of time (let there be light), creation (Designing API), it is about existence and life (ANIMATION), about humans ("Newbies"), human behavior (ALGORITHM) and "soul" (Source Code)

-its about some supposed "alien" being or some kind of "Architect" 'type of person' - French, Verb. clames - 1. Second-person, singular, present indicative

- it is about the problem, about choice, emotions and truth ..about right and wrong

[ synopsis: after some time of absence 'clames' returns to Earth and finds things ain't going quite as expected. the problem seem to be related to "afterlife" >"but the peculiar thing is that it also seem to try to deal with the reminder of the time after the iterations have finished"; ..'clames' obviously does not have ultimate power and it can not control the future and for some reason there must be a decision... ]

ok, let me explain,
its silly thing to say really, but i didn't mean to pretend as if 'i am' saying this, i just thought its honest and creative.. it just came out that way ;-)

but hey,
dont forget.. the algorithms are still real!

//------------------------------------------------
-"There are two doors. The door to your right leads to the Source, and the salvation of Zion. The door to your left leads back to the Matrix, to her and to the end of your species. As you adequately put, the problem is choice. " (theMatrix.t)

September 26, 2008
aye caramba!
forgive my cheekiness, its all bona fide.. humorous manner

>>"Could you tell me where i must search the answer?"
- are you too speaking in metaphors? if so, i believe 'the answer' lies within..
but, seriously tho, this thread should have answered all your questions - you came to the right place, it was quite a discussion, and there is this odd coincidence and fable about life, universe and everything..

>>"I wonder, if there is any limitation or peculiarity in havok i don't know about? Or its my fault?"
- i think you have a few things too many in that listing,
earlier on in this thread you can find a bit about 'Occam's razor principle'

(rename back to fit)
it would seem, this should suffice:
//-----------------------------------------------------
#define STEP 0.02f
static float accum;

void simulateAndRenderOneFrame(double deltaTime)
{
accum+= (deltaTime < STEP*2)? deltaTime : STEP*2;
while( accum >= STEP )
{
m_world->stepDeltaTime(STEP);
accum-= STEP;
}
renderScene();
}
//-----------------------------------------------------
//--> deltaTime= TIME_SINCE_LAST_FRAME <--!!!
//--> if slow, try larger STEP (0.033, 0.067, 0.1..)

..experiment with STEP and make sure that you pass correct deltaTime ..in addition you may try to understand what was already said here, but that is not really necessary.. let us know how did it go

September 26, 2008
>>"I think the main point of this somewhat blo.."
- im afraid you misunderstood,
not quite sure what your question is as you seem not to be asking.. but actually suggesting something somewhat opposite of what im trying to argue here?

if you're considered about "bloat",
having the generality of your answer and the proximity of the message, you should realize that quoting the whole question was superfluous ..plus, you're wrong, which makes your whole message a piece of bloat actually

please.. please, lets clear this up,
call your boss or someone else who knows..
its quite an important issue, so its only fair to address these questions first:

- would you agree algorithms i propose address and solve the mentioned THREE problems? (YES/NO)
- whats your opinion on how they works in practice - visual appearance compared to original? (DESCRIBE)

until this is proven false,
your information is no less wrong than mine

cheers

September 27, 2008

this is not about Physics at all..

-"You think that's _air you're breathing now?"

..you know,
i just wrote a new book on these matters..
everything is still told in metaphors in this book,
just like it was all along and as it is right now, there is no time like present, they say...

[MISSING-REPEAT]

..the most of the rest of the book is actually right in front of you as i explained before while pointing out some of the metaphors.. the book ends with this quote, already referenced couple of times in the above discussion:

-"I know you're out there.. I can feel you now.
I know that you're afraid. You're afraid of us,
you're afraid of change..

I don't know the future..
I didn't come here to tell you how this is going to end,
I came here to tell you how this is going to begin.

Now, I'm going to hang up this phone,
and I'm going to show these people what you don't
want them to see. I'm going to show them a world
without you..

...a world without rules and controls,
without borders or boundaries. A world where anything is possible.

Where we go from there.. is a choice I leave to you..."

------------------------------------------- The End -------------------------------------------

abaraba1@yahoo.com
http://www.oocities.org/ze_aks/myos.htm