> I was in the quest to program the perfect algorithm, but.... I CREATED A
> MONSTER!!!
>
> ha ha ha...
>
> Before, my algorithm didn't consider the conservation of the cloth's
> velocity (in each vertex of the mesh), and I thought it should, and I
> rewrote major parts of my code to allow this. But obviously I did
something
> wrong, because this looks AWFUL!
>
> I hope I can be easily fixed...

I hope so - it looks so good to start with, very fluid.


--

Rick

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*lool*
That's indeed a funny one.
For me, it looks like it repells from itself and the surface without any
loss of energy. It has no inner friction anymore, similar to a fluid. Maybe
a little bit of "rubber-cloth" *g*

regards
SY

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"Peter Popov" <pet### [at] vipbg> wrote in message
news:im4l4ugpvb45knh0ruj5b3p8s191lsk3gv@4ax.com...

> <fcu### [at] yahoocom> wrote:
>
> >Before, my algorithm didn't consider the conservation of the cloth's
> >velocity (in each vertex of the mesh), and I thought it should
>
> Err... it is energy that has to be conserved, and momentum, not
> velocity. Of course velocity will be conserved if there are no
> external forces, but then the animation will be rather dull, won't it
> :)

Hi Peter,

Tomas Lake made a similar observation, so I'm reposting my answer:
{
I did not expressed myself properly: I'm really not trying to conserve
the velocity. My first algorithm did an estimation of the motion directly
from the forces, not with the velocities. I thought that having explicitly
the velocities would improve the behaviour of the cloth.
}

After much struggling with the results obtained from this theory I believe I
will return to my old style simulation.

> If I were you, I'd use some sort of feedback to keep the energy and
> momentum of the system from growing beyond what is expected from the
> influence of external forces. You will thus eliminate most of the
> discrete integration errors, which are especially painful in the
> forward Euler, which I believe you use (everyone does on their first
> try at cloths :) )

Yes, I'm using forward Euler. Yesterday I gave a big thought on how to use
other solving methods, but I haven't implemented them. I hope I can find
some time to test these new ideas.

Thanks for your comments!

Fernando.

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Okay, i don't even know what forward Euler is, but i'll give my intuitive
two cents and risk sounding like an idiot.  What if you multiplied the
velocity of the cloth by a constant x such that 0>x>1 every iteration, or
when the cloth is transmitting energy to itself, so to speak, you did the
same sort of thing?  It looks like it's retaining it all, never coming to
rest.  The initial rippling does have some realism to it, in a way that the
previous animations don't, maybe a fix of that sort would be an effective
middleground?.  in any case, it looks a whole lot like water, which is very
neat.  i like it, realistic or not.


news:3c4a2e8d@news.povray.org...
> I was in the quest to program the perfect algorithm, but.... I CREATED A
> MONSTER!!!
>
> ha ha ha...
>
> Before, my algorithm didn't consider the conservation of the cloth's
> velocity (in each vertex of the mesh), and I thought it should, and I
> rewrote major parts of my code to allow this. But obviously I did
something
> wrong, because this looks AWFUL!
>
> I hope I can be easily fixed...
>
> Fernando.
>

Post a reply to this message

<fcu### [at] yahoocom> wrote:

>Yes, I'm using forward Euler. Yesterday I gave a big thought on how to use
>other solving methods, but I haven't implemented them. I hope I can find
>some time to test these new ideas.

Try implicit Euler first, as its simplicity is next to that of the
explicit (forward) Euler method, though it's much more stable. I don't
know how this will affect cloths, I know it affects solids in a
realistic way, i.e. avoids unrealistic stress concentrations.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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Hi Michael,

I'm glad you liked it, even though it was quite bizarre.

About your suggestion, I also thought of using a similar idea, in which I
would slowly "dampen" the velocity and loose that energy. However, (please
don't kill me) I don't remember very well what where the exact results of
this modification, but I do recall that it didn't solve the problem as I
wanted so I discarded it.

I'll post soon my latest experiments, which I think you will like.

Thanks for your ideas and comments!

Fernando.

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"Michael McKnight" <nes### [at] hotmailcom> wrote:
[...]
> velocity of the cloth by a constant x such that 0>x>1 every iteration, or
[...]                                             ^^^^^

ahem ???

--
[Talking about cardriving]
"People are opstacles?
Oh...I always treat them as bonus points..." [Ian Burgmyer in p.o-t]
// Jan Walzer <jan### [at] lzernet>

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what?
sorry i emailed you on that one, i'm a bad OE user.

"Jan Walzer" <jan### [at] lzernet> wrote in message
news:3c4c0722@news.povray.org...
> "Michael McKnight" <nes### [at] hotmailcom> wrote:
> [...]
> > velocity of the cloth by a constant x such that 0>x>1 every iteration,
or
> [...]                                             ^^^^^
>
> ahem ???
>
> --
> [Talking about cardriving]
> "People are opstacles?
> Oh...I always treat them as bonus points..." [Ian Burgmyer in p.o-t]
> // Jan Walzer <jan### [at] lzernet>
>
>
>

Post a reply to this message

"Michael McKnight" <nes### [at] hotmailcom> wrote:

> what?
[1]

> sorry i emailed you on that one, i'm a bad OE user.

yeah... it seems so ...
for the email-thingie: You know, that you can customize the toolbars for news
independant...
I, for myself, deleted the ReplyToAuthor-Button, so it won't happen again ...

The other thing with outlook is, that it places the cursor at the top, and
cites the
whole message:

But for us humans is should be possible, even to correct this. Simply go down
with the
cursor, and delete every line, in between, that has nothing to do, with the
answer,
you're 'bout to write.

If you want to answer a special sentence, feel free to do so, in between.

Sorry, if you already knew this, but I think it was worth to mention... no
flames intended


> > > velocity of the cloth by a constant x such that 0>x>1 every iteration,
> or
> > [...]                                             ^^^^^
> >
> > ahem ???


[1] I'd prefer to write 0 < x < 1 ... (because 0 < 1, you see ?)

--
[Talking about cardriving]
"People are opstacles?
Oh...I always treat them as bonus points..." [Ian Burgmyer in p.o-t]
// Jan Walzer <jan### [at] lzernet>

Post a reply to this message

> Sorry, if you already knew this, but I think it was worth to mention... no
> flames intended

no problem, i'm really not feeling the heat.  :)

> [1] I'd prefer to write 0 < x < 1 ... (because 0 < 1, you see ?)

wow, i didn't even catch that.  i suppose i should pay more attention.

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