Problems with hair / polymer chains representation

Hello,

I would like to represent entangled polymer chains inside a box (or entangled ropes or snakes or whatever). The chains should be randomly distributed inside a transparent box. I tried this with “hairs”, randomized by a brownian motion, but I did not manage to confine the hairs inside the box… How can I manage what I want to do ?

I also would like to represent a crosslinked polymer network inside a 3D transparent box. For this I don’t even have a starting point… How to do ?

A last question : I don’t manage to make an animation where hair grow, for example out of a head. I created an IPO curve for increasing the “Brown” parameter, but the curve does not seem to be taken into account. Is there a possibility to do this ?

Best regards,

O.C.

Hmmm… I’m not really sure what you mean by “polymer chain”, but if you want a linked metal chain, you can create rough chain links and hook them together and simulate them in the Blender Game Engine. Create normal low res chains, link them, then add subdivision, don’t apply the subdivision, then simulate them falling into the box, and that should give you a good result… that’s the only way I could think of at the moment. I don’t have time to try it out myself but I’ll be back to help you out in about an hour and a half.

Hello,

the term “chain” is misleading. I used it because it is the usual term in chemistry, but it may not have been the best choice. In chemistry, a “polymer chain” is often represented by a simple wire or a simple tube of small diameter. Entangled chains fill the whole volume and there are a lot of them. In fact the best comparison is a plate of spaghetti !

So my question can be turned the following way :

  • how to draw a box filled with spaghetti (with a bit of space around each pasta tube) ?
  • how to draw spaghetti which bifurcate at several places (1 tube becoming 2 tubes) ?

for growing hair out of a box!

you could animate curves with particules system i think

cn you show some pics of what your rying to do might be easier to understand and see what you mean if you can

also there is a script to represent molecules using the way chemist represent these things
but don’t know if this can be applied to polymer !
search the blender nation for it

and cross link polymer still unknow don’t even remember how it looks like !

but i would definitively like to see this an example of this
it might be usefull in futur for other peoples

happy blendering

I did not manage to have hair sprout out of a head. I manage to have hair flow with varying wind or be attracted by varying electrostatic force, but I did not manage to change their length with an IPO curve.

Here is a nice image of slightly entangled polymer chains [from Alexei Likhtman]. Pretty much what I would like to show ! However, in a first attempt, I wouldn’t mind if the chains intersect each other (the self-avoiding chains are certainly harder to calculate)

Here is the idea of crosslinked chains :
http://pre.aps.org/files/cover_image/PREv78i0508.jpg

Does anyone has an idea for building this ?

i can see 2 ways

1 - manually add and edit curves lines
i guess you dont wont this one
or may be a a last solution
it takes longer to do it !

2 - try to do it with particules or hair system

i know it would be longer to do it manually but would allow more control over the location fo each curve and not cross over or criss crossing may be

now it may take some times to experiment with particules or hair system to do this
i’ll try to do some and bring it back here as sample file
but this may take a few days how your not too much in a hurry here!

by the way i’ll do it with 2.49 not 2.5 hope you dont’ mind

2.5 is going to have some changes to particules system so getter wait i guess

so i suggest to check out often to give comments and crits
so we can advance with this model

i’ll try to make one this afternoon later on

Happy blendering

A nice way would be a python script, but I’m not at that level for the moment !

I tried in this direction but gave up because I did not manage to confine the hair inside a box. If you have something I will be very interested !

don’t think a script would be good here
still need to constraint inside a box

mind you that there is the vortex that might do that by keeping the rotation radius insdie teh box but have to experiment with this effect !

may be with a lattice box
http://wiki.blender.org/index.php/Doc:Manual/Modifiers/Deform/Lattice

have to test and see results

salutations

here a first test

with some curves object and particules

see pic

but too regular i guess

ok got some random in space
see pic 2
do you need any texturing on theses ?

salutations

Nice ! How did you do ? Is there a possibility to add a random rotation for each individual polymer ?

do you need any texturing on theses ?
I won’t need texturing for the moment.

Best regards.

here is a sample file
i set only one layer but it could be more then one layer of particules
with several curves giving a more full filling effect
but still it does no respect the cube itself !

i’m also looking at the hair system
this may be another way to do it but have to experiment a little

salutations

I looked at your file and understood how you did : a particule system of objects.
It is indeed difficult to confine this in a box. That’s why I was thinking of a script. I remember I read about a script which could create random vertices inside an object. A slight adaptation could do the jobs (random position + random orientation). However I can’t find that script again.
Let me know if you get something with a hair system !

for script may be open a thread in python forum
may be someone will remember it ?

i’ll e back with hair system and see what it gives

but still not limited to a box
but there is also the keyed particules that might be used i’ll test some more
salutations

Hi, now, after reading, I think I have the level to write a script for this. I may do this in the coming weeks if I find time. However, I am still interested by your ideas about hair.

her is one with hair + curve from a vertical wall

now i did not comb the hair but you can do this i guess

so that should easily confined theses into a cube

salutations

Hi, thank you for this file. You used a particule system with hair and objects.
I feel that the result is too regular. I have not found a particule system giving random orientation of the objects. Some randomness is offered, but it is always too regular.
So I’ll go for a python script. I’ll come back later. Thank you for your help.

Hello,

I wrote a python script which can represent linear or crosslinked polymers (in more general terms, random walks or random networks). It requires numpy.
Example: the following image represents linear polymers inside a torus and a crosslinked polymer inside a sphere.



The code is in the file polymers.py.blend (34 KB) (remove the .blend extension which I just added so that I could upload the file here).

by the way i kust leanr that there is a thread type for particules
but not certain where it is !

i loaded the file but there is no script inside

can you upload it please

thanks

Hello,

> i loaded the file but there is no script inside

for me it works. Just clic and “save as”. The file size is 34817 bytes.
Could you please try again ?

sorry i misread you post

i forgot you added the blend extension after

so i remove it and i got the script

did you check the new thead option for particules systems ?

the pic your showing is not exactly a random threads in space
it’s very specific organisation in space of molecules i think
mind you i’m not in chemistry just know things in general of this field

also you i remember that there is a special script to make molecules
did you see it ?
but this was in 2.49 last year

Thanks