PIPE­LINE TECH­NIQUES: hair an­i­ma­tion in hou­dini

3D Artist - - CONTENTS -

Alla Chernova on how to cre­ate mer­maid hair

This tu­to­rial will show­case one of the tech­niques for hair an­i­ma­tion. it would work the best for a static char­ac­ter or a mi­nor an­i­mated one, such as my mer­maid. The mer­maid uses float­ing an­i­ma­tion, with­out any ad­di­tional char­ac­ter an­i­ma­tion on the up­per body.

i find Red­shift suits my needs bet­ter than any other ren­der soft­ware, mostly be­cause it al­lows an eas­ier tran­si­tion from Maya to hou­dini and back by us­ing Red­shift proxy. There­fore, for this tech­nique to work, make sure Red­shift is in­stalled for both Maya and hou­dini. it is an easy and use­ful tool for any cg gen­er­al­ist to utilise, with­out need­ing ad­vanced knowl­edge of hou­dini or FX.

We will start from cre­at­ing hair geo in Maya us­ing Xgen, then move to hou­dini for cre­at­ing an an­i­ma­tion it­self, and fin­ish with ex­port­ing Red­shift proxy back to Maya.

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Cre­ate a hair style with Xgen The new Xgen in­ter­ac­tive Groom in Maya is a great tool to cre­ate any hair style you wish. i use the brushes from a screengrab, heav­ily re­ly­ing on freez­ing most of the hair and work­ing from curl to curl. To start, se­lect the scalp faces that will have hair, ex­tract them and cre­ate, from a new geo, the in­ter­ac­tive groom­ing de­scrip­tion. if your char­ac­ter has an­i­ma­tion, you will want to cre­ate a de­scrip­tion on the first frame. Af­ter you’re sat­is­fied with the shape and vol­ume, con­vert in­ter­ac­tive Groom to poly. i did it as one mesh, so Maya can han­dle it eas­ily.

02

Rig hair for the char­ac­ter The mer­maid float­ing an­i­ma­tion is ap­plied to a box, and the mer­maid is par­ent con­strained to it. This way, the ren­dered mesh can be edited or changed at any point, be­cause it doesn’t have baked an­i­ma­tion. For the hair to fol­low the mer­maid, i con­strained it to the box as well. now we have the char­ac­ter with static hair which moves in sync with the body. To move to hou­dini, i ex­ported OBJ of the mer­maid’s body and hair from frame one. This puts the an­i­mated hair in the start po­si­tion, re­plac­ing later static hair in the con­straint.

03 Pre­pare mesh in Hou­dini for an­i­ma­tion To start in hou­dini, i made sure only the tips of the hair geo would be af­fected by noise an­i­ma­tion while the roots stay still. i cre­ated a black/white mask. i sep­a­rated body and hair by us­ing a delete node.

By se­lect­ing hair faces and hit­ting delete over the view­port, blast nodes iso­late the body. By du­pli­cat­ing and in­vert­ing se­lec­tion, i used the same node to iso­late the hair. On sep­a­rated geo i ap­plied black (hair) and white (body) colours ac­cord­ingly. com­bin­ing those two branches with trans­fer at­tributes node al­lowed me to cre­ate a black/white gra­di­ent on the hair.

04

Ap­ply tur­bonoise on the po­si­tion val­ues VOP is a node-bas­ket where i build my an­i­ma­tion net­work. By cre­at­ing VOP in­side i’m get­ting two nodes for my in­put and out­put pa­ram­e­ters. The pa­ram­e­ter i’m go­ing to use is P – po­si­tion.

By cre­at­ing a tur­bonoise node, it cre­ates a black-and­white noise pat­tern. Adding tur­bonoise over P will tell it to off­set the point po­si­tion us­ing noise colour val­ues. in or­der to keep the roots still, i had to mix val­ues of in­put P, that al­ready have a mask i’ve cre­ated with the new po­si­tion val­ues with off­set af­ter the add node.

By set­ting P in the sec­ond in­put, it tells noise to not af­fect the white part of the mask.

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Al­ter noise val­ues For the an­i­ma­tion to look more or­ganic, i added three dif­fer­ent noises on top of each other. The most im­por­tant pa­ram­e­ters to ad­just are: fre­quency, size and time. First, i use a small fast noise, then a medium noise a bit bigger.

On top i added big waves to cre­ate a float­ing feel­ing. it is a good idea to play­blast the noises in­di­vid­u­ally, be­fore com­bin­ing them. For the hair an­i­ma­tion to look smooth, use plenty of geo sub­di­vi­sion. if it’s not enough, you can smooth it in Maya and reim­port the geo.

06

Ex­port Red­shift proxy back to Maya To set the mer­maid scene in Maya, i needed the hair an­i­ma­tion to be ex­ported from hou­dini.

The best way of do­ing this is to cre­ate proxy, which brings in a bound­ing box in­stead of heavy an­i­ma­tion of high-poly geo. To ex­port proxy, i went to Ar­chive in the Red­shift ren­der set­tings, iso­lated the geo i wanted to be­come proxy and ren­dered the se­quence to disk with the cor­rect num­ber of frames. When im­port­ing Red­shift proxy back to Maya, i needed to set up these pa­ram­e­ters for the proxy (image 06). now i can as­sign shader and ren­der the se­quence out.

Alla Chernova artstation.com/allachernova Bio Alla is a 3D gen­er­al­ist. She has a back­ground in tra­di­tional art who stud­ied 3D at the Gnomon School of Vis­ual Ef­fects

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