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Vellum - animated Pin to Target?

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I am struggling to find a solution using Vellum that allows me to modify which points are part of a "pin to target" constraint over time, or their overall strength.  There seem to be workflows for modifying attributes for other types of constraints that work (using a sop solver in DOPs to modify stretch stiffness, etc), but those same methods do not seem to work with Pin to Target. Essentially, I want to be able to have my vellum object pinned to animation in specific locations on specific frames, then over time, change which points are being constrained (usually I would be removing a sub-set of the points, allowing more of the geometry to simulate freely). 


Rohan Dalvi has a great tutorial that goes over a similar workflow using "Stitch Points or "Weld Points" and modifying the Breaking Threshold over time, but this method does not seem to garnish any results when you flip to the "Pin to Target" constraint type. (Link to his video: https://vimeo.com/296601872)


Am I just doing something wrong? Does this feature not exist? Maybe there is a different constraint type that would allow me to pin to animation? Any help would be greatly appreciated!





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Hi Ben,

I'm having the same issue here. Were you able to find a solution?

I also want to update the constrained points over time but it seems like it's not working with the "Pin to target" constraint type.

I've attached a very simple scene.. Basically I'm just trying to transfer an attribute from an sphere in order to detach strings over time.

Any help much appreciated! Thanks!


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You could use targetweight on your points, which is a float variable, and animate that (see the help on grains for that matter). I tend to create a Pin to Target constraint, setting Stretch>Stiffness to Scale by Attribute and targetweight as control attribute.

Also set Pin Type > Soft, Orientation Pin Type > None and activate Pin to Animation.

This should allow you to control the pin strength by animating the targetweight attribute.

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Thanks for your help Ernest, really appreciate it!

I tried what you said and it seems like I'm still not getting it. No matter which attribute I'm animating in SOP, it's not updated over time in Vellum.

I updated my scene applying your advice. Is there something I'm missing?

Thanks a lot!


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I'm struggling with the same issue at the moment. What's strange is that I'm perfectly able to do it the other way around; having 0 pin to target on all points, then adding pin constraints throughout the geo with an animated attribute transfer in a sop solver within the dop network. Then using the dop vellumconstraints, set to update on each frame, to create the pins throughout the simulation. Must be something I'm missing here...

Any insight would be greatly appreciated.


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I know it's been a while but I ended up finding a solution through an older odforce post from vtrvtr.

Basically you want to set a group of points in a "Pin to target" constraint and animate the breakthreshold attribute in sop.

In order to transfer the attribute from sop to your ConstraintGeometry in dop, you need to plug a sop solver in your vellum solver. You will need to check "Invoke Compiled Block" on your sop solver node and add an extra output for the ConstraintGeometry. Inside the sop solver, you'll need to copy the breakthreshold attribute from sop to the ConstraintGeometry.

Maybe there's another way, but it's the only way that worked for me so far! Thanks Vitor!






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Thank you very much splegare and Vitor! That worked great! Never would have figured out that solution by myself. And thank you for sharing the hipfile(needed that).


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Using a SOP solver to generate the animated attributes...
I am doing a similar thing, with pin to target but using @stretchstiffness / match animation to modulate the constraints. 
I have it working, but for the constraints to be working I have to remove the constraint every frame with a VCP node, and rebuild it, but match to animation doesn't work. 
If I kill the VCP remove then match to animation works but the animated constraints don't. Which kind of makes sense. 
I will crack it at some point!
I take it the only reason you need compiled block is so the SOP solver can output both Geo & Constraints seperately? I am a bit confused, I thought the SOP solver would take both automatically and spit both out. I am guessing not as they are individual data streams.

Any help appreciated. Hipfile included.




Edited by Jim M
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