Rig and simulate Hair Curves on Blender 3.3

(copy/paste of what I have posted on reddit)
The required geonodes to make rigging and dynamics hair(with cloth sim) possible are in this file https://studio.blender.org/films/heist/gallery/?asset=6072

Hair_deform & generate_proxy

Create any mesh and add generate_proxy then select the haircurves & apply it
Put Hair_deform on the haircurves and select the proxy you just generated

(If you do any modification to any of those objects, you must re-generate another proxy, you can still add additional genodes that can modify or add additional curves, but it must be under hair_deform)

Also the generated mesh will have a lot of vertices, so you need to optimize your hair curves and use geonode to generate more children https://www.youtube.com/watch?v=dUuRmcUQK_s by Johnny Matthews

It’s the same concept as this tutorial https://www.youtube.com/watch?v=W97e8xIVoqE by Nick Burkard

But using geonodes

To Simulate hair with cloth physic

You need to create another proxy for the proxy and extrude faces, otherwise you won’t have any collision. Also it easier to weight paint faces than invisible vertices

Update: Surface Deform need to be the last modifier for interpolated hair curves to work, you will also need to activate the checkbox for: ‘Surface Rest Position’ in the interpolated hair node nvm doesnt work with hair_deform, sorry for the bump

Only if the body or scalp is using armature modifier. This doesnt apply if you are using Child of constraint/Armature Constraint, you wont have hair shifting/moving issue with constraints.

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Step 0. this guide assumes you have surface deform geometry node already

Step 1. append the geometry nodes from https://studio.blender.org/films/heist/gallery/?asset=6072

append these nodes too: https://johnnygizmo.gumroad.com/l/habif by Johnny Matthews

Step 2. Make a backup of your hair curves. Optimize your curve hair, if you want to have dynamics hair(w/ cloth sim). Use the density brush. Separate the hair into multiple section if you have to.

If you choose to skip this step, you can still rig it, but your proxy mesh will have way too many vertices and your viewport performance won’t be great

Use the geometry nodes that you just appended to generates children(if you know how to create interpolated children, it would be even better, I don’t know how to do that.)

Step 3. Turn off any geometry nodes that can generate children, apply them if you have to(resample can be applied), because the Generate_proxy will create an exact copy of your hair curves with its visible nodes.

Add a hair deform geometry node and move it above. Geometry nodes that can generate or move the curve need to be under hair_deform

The Hair_deform requires a proxy to work correctly
Turn the visibility off for the hair_deform for now otherwise you cannot use the generate proxy.

Step 4. Create any mesh(Suzanne, Plane, Grid…) and add a geometry node then select the generate_proxy
image


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select the hair curves
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apply it
image

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Step 5. name your proxy


Do not edit the mesh! You can add an armature modifier, but you won’t be able to see your weight paint, because there is no face. you can assign it to the hair_deform and turn back on every nodes that aren’t visible

Step 6. Duplicate your proxy and name it

Select the mesh you just duplicated and go in edit mode select everything and extrude by 0.001


(OPTIONAL for the cloth modifier)Do not let go of your selection. Create a vertex group and assign them, it’s for the cloth modifier


Add another vertex group and call it whatever you want. I named it “pin” though.

Weight paint it


Set the cloth modifier, I am no expert in blender sim, I find it most of the time buggy. maybe someone has a good preset that they can share.
image

Step 7.Add Surface deform to the original proxy and select the proxy with the cloth modifier.

Make sure to bind it with no deformation, so go back to frame 0 or 1 and bind it. (because of the cloth modifier)

Step 8. TURN OFF ray visibility for cycles and set the viewport display(EEVEE & Cycles) as wire for the the proxies

Step 9. Make sure turn back the hair curves and its geometry nodes. if you follow correctly and I didn’t mess up you should at least have something like this, when you add an object with the collision modifer

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Step 10. If you do not want clipping hair, you can add this geonode:“Curves Aboves” by Johnny Matthews and add these nodes to the geometry node(I have no idea if this is the best way to edit it, Geometry node is still too complicated for me)

you can add a “resample” to make the hair a bit smoother again and reduce hair clipping through mesh.

Sorry I did not cover the rigging part, but it should be like this https://www.youtube.com/watch?v=gTdRGZA4TXA

DON’T FORGET to parent the proxies to the “head” bone or Data transfer the vertex group from the body mesh and then assign an armature

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If the hair are flying around, then select the vertices from the denser area in edit mode and add some of them into the no_self_collision vertex group or don’t use self collision

Or redo it from Step 2.

This post is underrated. Not many Blender 3.3 hair guides out there. Thank you!

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This is pure gem for GN hair simulation. advanced skill. Thank you for your detailed explanation.

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Better method here by munorr:

https://munorr.gumroad.com/l/bgen

edit:
no longer free
but not that expensive https://munorr.gumroad.com/

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B-gen is amazing but it only works for hair & braids, not for a piece of fur or beard, as it should deform with the body (facial animation/shapekey anim, armature/surface deform modifier ect…) For this the Hair_deform & generate_proxy method from the Einar demo file is supposed to work, but in my test the Hair_deform node setup makes the curves disapear when doing anything in the scene. (rendering, hiding any collection ect…) it works when turning the hair_deform off and on again, but as rendering a frame makes it disapear again, you’ll only see it in viewport.
In my case it’s for example a piece of fur on the clothes, the proxy generated with the node setup is driven with surface deform by another proxy of a portion of the body.
So in viewport I can see it seems to work, but the fur vanishes when doing anything includidng rendering, until turned off and on again.

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Does this problem appears in 3.5.1 version?

ah nice it seems to work in 3.5.1, but only if we move frame by frame, jumping on a frame in the timeline doesn’t synch the hair_deform on the right frame. Or maybe it just takes some time to snap into place.