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Sanctuary
02-05-2003, 11:11 PM
hi guys, i need your help on this one, but first i must apologize for my english (not my mother language). The problem is that i need an electric cable with real gravity effect, below is a list of ingredients i use in my scene:

- 2 locators (to control ends of the cable)
- 1 NURBS curve with 6 CVs (to deform the cable)
- 6 clusters, 1 on each CV of the curve
- 1 NURBS cylinder with lots of spans for good deformation
- 1 wire deformer (put on cylinder and curve and Local influence = 1)
- 1 poly floor (passive rigid body)
- 2 little poly cubs (active rigid body)
- 1 gravity field

To deform the cylinder i`ve decide to use an wire deformer, so i`ll use that curve for this. To produce the deformation i`ve put a cluster on every CV of the curve (which is wire deformer). Now i`ve start to point constrain the clusters like below:

cluster_1 constrained to locator_1 (constraint value = 1)
cluster_2 constrained to cluster_1 and cluster_3 (constraint value = 0.5 for both)
cluster_3 constrained to cluster_2 and cluster_4 (constraint value = 0.5 for both)
cluster_4 constrained to cluster_3 and cluster_5 (constraint value = 0.5 for both)
cluster_5 constrained to cluster_4 and cluster_6 (constraint value = 0.5 for both)
cluster_6 constrained to locator_2 (constraint value = 1)

to use the gravity effect i`ve point constrained cluster 3 and 4 like below:

cluster_3 constrained to cube_1 (constraint value = 0.5)
cluster_4 constrained to cube_2 (constraint value = 0.5)

well every thing looks good but i want to be able to make the NURBS curve to have a fixed length, i mean if i move locator_1 up in Y i want cube_1 to follow according to curve length instead of stretching the curve, so i need to limits the gravity effect on the cube_1 in some way. Now the cubes don`t stop until then reach the floor and that`s not good.


any help, suggestion, comment will be greatly appreciated.

here is the .mb file (use right-click -> Save Target As ...)
http://xr1140.3x.ro/test_file.zip
Sanctuary
02-05-2003, 11:15 PM
screen shot
mark_wilkins
02-05-2003, 11:21 PM
You could add a few more CVs to the curve and use pin constraints to keep the clusters a constant distance from each other. This would not give you EXACTLY a fixed length over the curve but it might look realistic.

-- Mark
Sanctuary
02-05-2003, 11:29 PM
it look realistic enought (dl the file and take a look)

... i need to animate the locator_1 and the cable to follow but not to stretch it ... so i need to limit the effect of gravity field so the cubes will stop before riching the floor
mark_wilkins
02-05-2003, 11:34 PM
I'm sorry, I guess I don't understand what you are asking. I thought you were asking how to keep the cable from stretching past a constant length.

-- Mark
Sanctuary
02-05-2003, 11:36 PM
well that`s one of the ideas ... if i can keep the cable to not stretch too much, i think i get what i need ...
gas
02-05-2003, 11:46 PM
Hi,
Well I write this from a vage memory deep down my head OK but I did a reporters microphone cable once and the reporter was moving around like hell... never mind.... I think I extruded along a path and then I made that path a softbody, with one of the options there and added springs ( I think that was pretty important for the effekt of keeping the same length) to all the CV with some settings, cant remember what but once you get it you know what way to work, but the start and end was lika "dont move" and constrained to a locator so all I did was moving the locator and the cable was working fine, a lot of fiddeling with collision stuff on the floor but it worked better then expected from try one. My problem was that it moved around alot, curved the cable over itself etc. and that made it hard but in your case it should work nice...
sorry I dont remember exactly what I did but in general thats it. gravity ofcource to get the "natural effect of weight" but that crystal clear....
good luck and prepare for many playbacks
gas
02-05-2003, 11:50 PM
hmm, maybe I missunderstood it all, didnt read it to well I mean, oups..
but maybe you could follow that line of working and just add a contraint between a cv on the softbody/springs and the cube...

good luck anyway...
Sanctuary
02-06-2003, 07:32 PM
any other ideeas ? :applause:
alexx
02-06-2003, 08:03 PM
1) how bout adding springs?
2) use cloth if available - there you have control on how much the result stretches

cheers

alexx
Sanctuary
02-06-2003, 09:02 PM
i`m trying springs now, and cloth need too much cpu power
Sanctuary
02-15-2003, 02:07 PM
i`ve solve the "problem", here is the answer (http://xr1140.3x.ro/How_to_make_a_realistic_cable_tutorial.zip)
alexx
02-17-2003, 08:15 AM
is that link ok?
Sanctuary
03-03-2003, 08:03 PM
it`s ok .... use "Save Target As ... "
bambam
03-03-2003, 09:46 PM
I've done this in the past
if you want the cable to stay a fixed lenght scrap your current approch and try this.

ditch the wie deformer you dont need it
put clusters on the extrude curve and let history update it

create a poly cube at each cluster and pin contraint them together
move the pin piviot to each cube center (kind like like a hinge)

if the cable is attach to something make the cube passive

now point contrain each cluster to each cube
Sanctuary
11-11-2003, 09:34 PM
an HTML version can be found on VisualArt.ro (http://www.visualart.ro/tutorials/cablu/cablu.htm) database
Gremlin
11-11-2003, 10:20 PM
bah, you beat me to it!
i was gonna give you that tutorial!! (but from the looks of your first screen shot, it looked as though you were using that technique)

I believe what you were talking about was in the wire deformer node... something about maintaining shape and volume.
eitherway, that tutorial rox... only problem, is that the wire cannot collide with itself!!
Sanctuary
11-11-2003, 11:00 PM
... only problem, is that the wire cannot collide with itself!!

yes ... i know ... when i wrote it i did not need self-collisions, maybe i`ll extend it someday :D
Gremlin
11-12-2003, 12:06 AM
you made that tutorial?! my gawd, extend it like now! ....self colliding cable, would rock!! the possibilities are insane!! :D
Sanctuary
11-12-2003, 06:50 AM
ok, ok .... I`ll see what I can do :)
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