Point Deform Losing Orientation [SOLVED]

[GlennimusPrime]

I have a single Vellum hair with many points.

To help make the sim faster and also keep its rigidity, I've first resampled the hair before going into the solver.
Everything works well here, the hair is bouncing and coming to a halt exactly how I'd like it.

Next I'm using the Guide Deform SOP to transfer that Vellum dynamic movement back onto the higher res original curve.
This is where my problem starts. The point orientation has now lost its data. Is there any way to point deform one object to another and keep the point orientations correct?

I'll attach a simplified .hip showing the issue with both the correct and incorrect point orientations.

Any help is greatly appreciated!

Orientation_Problem.hiplc

Edited June 7, 2022 by GlennimusPrime

[ryew]

AttributeTransferring the orient attribute from the 3rd Guide Deform output seems to partially work, though a bit fiddly to smoothly interpolate.  However, you'll need to interpolate the orient from the low-res sim regardless since your high-res curve doesn't start with one defined, so perhaps it's a start (apologies if you've already gone through that route, no workarounds were mentioned)

 

[GlennimusPrime]

Thanks @ryew Apologies I did not mention I had tried this method already.

While working on the first level of hairs (I'm building a dynamic tree), each new level becomes less and less stable with this method unfortunately.

I think it is ok that the input curve comes in without the orient attribute, as it will always come out of the Vellum solver with one.

I tried many different ways again after posting this with no luck unfortunately - Another option I can try is sticking with just the high res input curve and cranking up the constraint iterations and substeps until the hair curve is rigid enough to be as solid as a tree trunk.

The only problem here is the sim time. Things start to get unmanageable when just a single curve needs to be 25+ substeps with over a thousand constraint iterations!

If anyone has any methods for keeping Vellum hair rigid I'd love to hear

[GlennimusPrime]

I ended up solving the issue by first using the Orient Along Curve SOP (which is an amazingly handy SOP that can do so much more than just this!) to first build the orient attributes,  before the hair curve goes into the Vellum network, then point deforming the low res hair curve back onto the high res one.