Make Some Cloth Points Follow A NULL? (handkerchief)

[Atom]

Hi All,

I am trying to leverage Cloth Follow Target. The icon shows exactly what I want. The center portion of a cloth grid to track a null. But when I walk through the steps by clicking the icon it never asks me to select the moving NULL that I want to follow.

The icon essentially makes a table cloth.

I have tried Pin To Body as well, but that tool expects my NULL to be a dynamic object. I want to use a keyframed NULL animation to sling a handkerchief around.

 

ap_cloth_follow_target_example.hiplc

[Atom]

The cloth drag example that ships with Houdini 16 is close, but the pin constraint does not seem to recognize all my points. It jumps to the upper-right corner of my selected points. I need the attachment to remain in the center of the selected points, preferably with some kind of soft fall off.

 

ap_attach_cloth_constraint.hiplc

[adrianr]

Feels quite hacky but might spur you onto some new ideas.. 

 

 

ap_cloth_follow_target_sopsolver.hiplc

[Atom]

Thank you Adrian.

That is very close to what I am looking to achieve. When I set it to Leather, I get a fairly nice looking simulation. Do you know of a way to make it track even better? It seems very laggy in tracking the point. Is that just the fabric setting?

 

EDIT: Ok, as I explore the scene more I see the Follow strength slider on the Attribute Wrangle inside of the SOP Solver.

Edited June 3, 2017 by Atom

[adrianr]

I'm just having a chat with friedasparagus about this on the Discord. He's thinking manipulating v directly isn't such a hot idea, so I'm trying to rebuild it with targetP. The lag is just because all I'm doing is getting the normalized vector between the point and the null and adding a bit of it to the velocity every time step, multiplied by the falloff set in sops so the edges don't follow as much as the middle, so it's not like a pinned "You're here, now go here" sort of thing. You can up the follow strength but it gives super funky results beyond a point, further reinforcing the idea that screwing with v directly might not be the best way to go.  

[adrianr]

So this is something using targetP and targetv with the targetdamping controlled in sops pre-sim, so you can pick which bit of the cloth you want to go after your null. I'm guessing the best thing to do is make sure your targetdamping in sops is a value between 0 and 1, which is then multiplied by the Target Damping parameter on the cloth object. 

This feels like a better way to do it, so maybe ignore the way I posted before 

 

ap_cloth_follow_target_targetP.hiplc

[Atom]

Yep, that works great. Thanks again for you help!

[Noobini]

20 hours ago, Atom said:

I have tried Pin To Body as well, but that tool expects my NULL to be a dynamic object. I want to use a keyframed NULL animation to sling a handkerchief around.

p_cloth_follow_target_example.hiplc

so i used the null to control a box, ie. my tabletop, make tabletop a collider...now i can constraint the cloth to tabletop's top faces...effectively, the null still controls the animation