Cutting with ClothFX or Reactor?

[phormis]

It is not the easiest thing in the world but I can tell you how to do it.

First off I have been meaning to post a tutorial for this on my site. Some one was asking me about how to do this and I posted this animation...

http://www.hyperent.com/Media/TearingCloth_2.mov

Mind you this was a quick and dirty example but it shows that it is possible.

You have the right idea about having two cloth objects.

You need to create a group for each vertex along the edges of the cloth objects. For this example lets say group001 to group050. Depending on how many verts you have along the edge to be "cut"

Then use a "Group" constraint and have the group001 on Cloth object A be attached to group001 on Cloth object B and so on.

Then what you do is animate the scissors "cutting" the cloth. As the scissors "cut" through the cloth you animate the group constraint from on to off. The group will no longer be attached to the other group and the cloth will separate.

It is tedious but it is possible. I have been thinking of writing a script to set up all the groups and constraints but I have been busy lately. As soon as I can I will try to create the script.

-Paul

[Blue]

This sounds like a job for clothReyes, just a matter of checking a checkbox to make cloth tear.

[Jimbo65]

Thanks Paul I will give that a try first... (I had better luck last night running two panels on the same piece of cloth, grouping the points together.. the simulation was much cleaner along the seam line, ussing two pieces of cloth tended to leave gaps in the seam.) I am not 100% clear on animating the groups on and off. But it should not be that hard to figure out.


Also ClothReyes is not that expensive and looks impressive, I may put that in the budget just in case it makes life easier... plus it never hurts to get some added plugins... I have downloaded the demo and will give it a try!

Thanks...

I will post again on my results.

Jim

[Jimbo65]

just an Update on the progress of this project.

ClothReyes was a big waste of money. I has nothing to offer in this situation, the tear feature of the colth was bogus, because it tears along the mesh polygons, which produces a jagged edge and it tears nothing like scissors cutting.

I am having great luck with ClothFX and group to group constraints. The big problem I am having now is the seam. No matter what I do, the constraint type for group to group and cloth to cloth is soft? so the verts open and close as the simulation progresses.

Paul, I was looking again at your movie and there is no seam in there?

How can I create these constraints without the seam opening up?

Thanks

[phormis]

First off, why don't you model the seam into the cloth and set clothreyes to tear at the seam when the scissors cut it?

On to how I did it.

I had three objects...

A) The left piece of cloth
B) The right piece of cloth
C) The two above pieces attached and welded together

All I did was skin wrap C to A and B. Then I used a visibility track to animate the visibility between the three objects (C and AB).

At the start the two cloth objects (A and B) are hidden then when they start to tear I hide the attached version (C) and I unhide the two individual pieces (A and B).

Since you will be cutting over a longer pieriod of time (I guess) you may need to use an animated map to handle the swapping, or perhaps a compositing software (Like Fusion).

Let me know if that helps you out.

Also, under strength for the group, I had a setting of something like 1000 to 5000. My two objects never did separate that much.

-Paul

[Steve Green]

If you're using Skin Wrap, couldn't you use a vertex weld modifier with a low threshold to dynamically weld the object so you don't see the seam?

I tried vertex weld before just on the cloth but it didn't like changing topology.

I just tried the skin wrap trick, but even though the source pieces separated, and the tearing cloth had a division, it didn't seem to want to separate (I guess I just need to play with the skinwrap weighting)

The main drawback with this method, is that the cloth could un-tear if the verts got too close again.

- Steve

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