cloth measures


#1

i’m using EzFlex, however i have a problem, i cannot estimate cloths’ sizes.
For instance, about what sizes a skirt can be? length? weight??
when i enter the length 0.5 meter and weight 0.5 kg it stretches too much and i cannot get the results i wish.
do you have any idea??
thanks…


#2

I am dealing with the same problem… Anyone outhere?


#3

The appendix actually does a decent job of explaining how syflex calculates the clothe.

It also has a java script calculator in which you input various numbers and it computes what the syflex settings should be.


#4

As I understand it…

input : L (length), T (time), M (mass), SA(surface area), TM(total mass)

         gravity = 9.81*(T*T)/L
         mass density = TM/SA 
         spring stiffness = 12500*(T*T)/M
         spring damping = 5*T/M
         global damping = 0.25*MD/T

Mass(M):

lb = 454
1/2 lb = 227
1/4 puund = 111
gram = 1
kilo = 1000

Time(T):

film = 0.041666
ntsc = 0.03333
pal = 0.0347078

Lenght(L):
mm = .01
cm = .1
m = 1
inch =.0254
foot = 0.3048

Surface Area(SA): 
mel cmd: polyEvaluate -area <mesh,selection>



 surface area part is interesting..

Say you make a default polyPlane
then run “polyEvaluate -area” on it , should return 0.999999, lets round that to a 1.

divide what you want total mass of your cloth to be by SA

I want the cloth to be equal to it’s SA, so…

1/1 = 1 , so that makes the pPlane1 mass density = 1.

Sounds and is really simple.

if your to run syInfo on your solver node, it would report something really close
to 1,

this works for any SA

say your SA is 45.121

45.121/45.121 = 1 , notice the massDenisty attr will be very close to 1.

If I wanted cloth to twice as heavy

(45.121*2)/45.121 = 2

massDenisty = 2

 lenght(L) only affects gravity..

From the above formula, notice (L) only affects gravity …
which will relate how heavy your cloth feels…

I’ve been useing inch lately (.0254)
not that my show/production is working in inches, but I
like the result it gives with what I’ve selected for mass.

 time(T) affect both gravity and spring stiffness

From the above formula, time is used for in every part except mass density,
I stick with what the projects working time unit is ( film in this case ).

 mass(M) affects springs stiffness, and spring damping...

I don’t know where 12500 comes from but that is what the syflex god suggests…

I’ve been using 1/4 pound lately (111)

So when you put this all together, I usually start with something like this…

$L=.0254
$T=.041666
$M=111
$SS=12500*($T*$T)/$M;
$SD=5*$T/$M;

mass density =1 ( TA/SA )

str = (($SS)(SA2));
shr = (($SS)(SA1.5));
bnd = (($SS)(SA.05));
str_d = (($SD)*(str)1);
shr_d = (($SD)
(shr)1);
bnd_d = (($SD)
(bnd)*1);

self envelope is a global umber so it denpend on your working units
so if your character is 6 units high (6 cm for me)
self env should not get mych larger than .1 for thickness

what I find interesting is once I’ve set the above values, I play with
M and L to adjust the feel of the simulation. It almost acts like
maya cloth scale and sample settings…

if I change
M=1000
L=.1

from inch and 1/4 pound

the cloth sims much loser…


#5

thanks a lot for this very useful information…


#6

also, a couple of things…

in the docs, the equations call for the use of $T
it is suggested that you use 1/fps. ie, film is 24 fps use 0.041666

this IS the case for inputs into the “caluulator”, however, this is only the case in some of the equations that the calculator uses internally, sometimes it actually uses 24

anyway… you only really need to know that if you are going to write your own calculator (which I recommend) because of 1 of jMartins points… and my next one…

everyone thinks the calculator in the docs is rubbish (sorry gerard) but is is actually correct… sort of…

Gravity - is correct
Mass Density - is correct (but you can change it)
Cloth Spring Stiffnesses - is correct
Cloth Spring Damping - is correct
Global Damping - is correct RELATIVE TO YOUR MESH

remember all the input information is about the scene NOT the mesh…
work out the relationship between the calculator output and your average faces per square unit (numberOfFaces/surfaceArea) and you will have a nice sim every time.
and even get presets working :wink:

.j


#7

I think this should be :slight_smile:
mm = 0.001
cm = 0.01
m = 1

Luca


#8

right u r , thanks for the correction,


#9

I’m writing my own calculator and I have been struggling with all the issues poeple have brought up. If it was possibly could I get some more clarity on this statement? Where would you use that number (numberOfFaces/surfaceArea)? How can I implement it into my calc? thanks a ton


#10

Hi friends.

am giving my sycloth values,

SA(surface area)=949 TM(total mass) = 976.523 Time (film) = 0.041666

Length=?( which value i need to take here)

What is the length how u r calculating L=.243 from where u got this value?

these all are my cloth values, Please explain something about how u r calculating the values of

$L=.0254
$T=.041666
$M=111==============which mass value?, is this syflex defult or any other mass ?
$SS=12500*($T*$T)/$M;
$SD=5*$T/$M;

mass density =1 ( TA/SA ) ===========what is TA ?

str = (($SS)(SA2));
shr = (($SS)(SA1.5));
bnd = (($SS)(SA.05));
str_d = (($SD)*(str)1);
shr_d = (($SD)
(shr)1);
bnd_d = (($SD)
(bnd)*1);

i went all these formulas still am not getting .

please explain me …

thx


#11

As a user u can always contact http://www.syflex.biz/ at support@syflex.biz

If u having problems trying to come out with those numbers just contact them they will help you. That is there job.


#12

TA is short for total area or total mass that value / surface area will get you the number to feed the solver mass attr

in your example, 949 is your cloth SA, if you want the feel of twice as much mass, putting
a 2 in mass attr will be = to 949*2/949

for mass unit…
111 is equal to 1/4 pound and is what I often use for my mass unit

454 is a pound
1000 is a kilo

the larger the mass unit the heavier cloth should feel/sim.


#13

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