Curtains & Chains - physics

TangoAlpha

Thanks Dudu. Your file does indeed behave as you say. But mine -- the best I can manage is all chain links disperse to the four winds!

That's bullet physics. If I switch to standard physics, Carrara just crashes.

I've also added the test .car file which produced the movie.

https://youtu.be/kru5be6xnr0

http://tangoalpha3d.com/files/ChainTest.car.zip

 

evilproducer

rock livrette said:

Do you have an actual version of Carrara? I remember physics going wild in older versions............well...mh...they still go wild..;-)...

Who? Me?

DUDU

Hi TimTangoAlpha!
Here are two evenings which I try to make the simulation of your file but without success…
But I saw a few things which could create problems:
- the links of your chain are in vertexes and you use the function “Smooth”, I believe that would be better to export them in .obj with the morphs and then, to import them.
- The hot points are very far from the bounding box of each link, it should be centered individually.
I isolated a part of your chain (15 links) and configured the others on “still” to make some tests:
The links fly away after one or two images, no matter the physical adjustments of the scene and the physics properties of the objects (materials).
I also made the same tests after having converted each link into “Primitive modeller”… same bad result… Grrr!
The tests which I made for myself were carried out with links in Spline objects, is there the solution?, I don't know but I arrive at good performances, you downloaded one of them, you could perhaps start again with that as basis?
I have an other urgent work to do for this time but I'll try again later.

TangoAlpha

Thanks Dudu. :)

The reason the hot points are like that is because it started off as a single vertex model (I find it easier to work like that) and I used Edit-> Split Object to break it into separate links
Taking off smoothing made no difference. My posts are open-ended (I take off the polys that are fully hidden) and I wondered if that would make a difference. Sof I filled in the ends. It didn't.
Then I brought your chain into my scene (had to scale it). Guess what? That flew apart too.

Even though there's' hust the fence post prop and a plane, I guess there's something screwy about that scene. So I took my chain and brought it into your scene. It didn't fly apart, but it does still break up into several pieces (see video). But it's progress!

https://youtu.be/rWb02QSvUeg

 

3DAGE

HI Tango Alpha

I don't know if you've solved your Curtain sim issues yet,, but here's a quick example scene, which may help you.

Your first thought of usign a box was almost right, but resizing the box won't work as weel as expected,. you need more boxes.

https://dl.dropboxusercontent.com/u/7907045/Curtains2_phys.car

I'm using a set of "curtain clips" (vertex box models) which are animated to open and close the curtain,

the curtains are attached to these using softbody attach modifiers.(one for each curtain clip).

I've made the curtains in the vertex modeller with a couple of lines and path sweep, ...so there is a pre-folded shape to them.

Generally,. the more realistic the conditions, the more realistic the simulation results should be,..  (given that it's a game physics simulation engine)

Anyway, ....Hope it helps :)

Also,. Carrara's own physics engine was always erratic,. that's why Bullet was added,

TangoAlpha

Thanks 3DAge. I've had to do other things for the past few days, so I haven't progressed any further. I'll take a look at your example tonight.

TangoAlpha

Okay, I've come back to this, having completely reinstalled everything in the interim. Surprise surprise, it all works! I just set attach points along the top to 5 box primitives per side, and moved them.

Now, how can I set the boxes to only start moving at (say) 2:30? I'l like the initial drape to settle before they open...

Hermit Crab

Simply go to 2:30 on the timeline and make a keyframe for each box.  Then move the boxes at a further point in time.  2:30 is quite long for a straight vertical drape to settle.

TangoAlpha

Thanks Marcus. The original mesh is not quite straight - there are a few kinks and bulges to give it a bit of motion (otherwise it just looks like a regular zig-zag. 2:30 was about the point where I thought it looked just right! (sans box motion)

3DAGE

HI Tim :)

You should be able to move the start keyframes for the boxes forward in the timeline,.so that the animation begins when you want it to

or Alt click, drag to copy thr start keyframes to 2sec's,. and make the tweener "discreet"

TangoAlpha

Thanks, that makes more sense - there was a little button labelled 'Make Key frames', but it didn't seem to do anything!

3DAGE

you need to manually create the keyframes by clicking in the timeline,. after selecting the (Add key frames) tool,.

Note :,. You need to re-select the (Pick) "Arrow tool" in the Sequencer,..  when you're done making keyframes,. Not the main Arrow (move) tool on the toolbar.

I still get hung up on that one sometimes.

Select then ALT+drag to make new ones is often less laborious

 

Generally,. moving the first keyframe in the timeline is ok, for most objects. apart from Figures like Daz or Poser imported figures, moving those initial keys can / will cause issues. ....best to use NLA to position the figure animation where you need it to happen.

Just a thought,. you could make your control cubes into an animated group, to get an NLA track and then you can use NLA clips to open,. close,. NLA's can play in reverse and you can change the timing for different instances of the same clip.