STEP BY STEP: Cre­ate wind-swept hair­styles in Maya

Learn how to cre­ate re­al­is­tic fea­tures on a stylised model and make in­ter­est­ing hair­styles in Maya us­ing Xgen, Arnold and Zbrush

3D Artist - - CONTENTS -

Crys­tal Bretz re­veals her work­flow

The Xgen hair sys­tem has been the top choice for many artists lately for cre­at­ing hy­per-re­al­is­tic hair­styles. Like many groom­ing tools, Xgen can be a bit of a chal­lenge to learn, but once you get the hang of its great tools you can cre­ate beau­ti­ful hair with ease. In this tu­to­rial you are go­ing to learn how to cre­ate a wind-swept hair­style us­ing Xgen, Maya, Arnold, and Zbrush.

This tu­to­rial demon­strates how to cre­ate hair guides from proxy geo, sim­u­late hair lay­er­ing us­ing Xgen’s clump mod­i­fier, and shade dyed and dam­aged hair in Arnold. You will also learn how to cre­ate stray and art-directed hairs for a fi­nal pre­sen­ta­tion of a still frame that sim­u­lates mo­tion.

01 Cre­ate proxy hair geo Be­fore start­ing any hair­style it’s good to block out a proxy geo. This can be ben­e­fi­cial for many rea­sons. In this par­tic­u­lar case we’re us­ing it to es­tab­lish the vol­ume of hair and how far it should come off the head and we’ll use it to cre­ate our guides from. This has been done in Zbrush with Dy­namesh for this in­stance but can be done in any 3D mod­el­ling soft­ware that you’re com­fort­able with. Once sat­is­fied with the proxy geo, mak­ing sure it matches your con­cept, we’ll Zremesh and ex­port the geo to bring it into Maya later.

02 Prep your scene for Xgen Now that we have our proxy geo we can start to prep our Maya scene to start with the Xgen. The first steps be­fore start­ing the Xgen is to triple-check that your project is set. This is su­per im­por­tant so that you don’t lose work and your Xgen maps save to the proper fold­ers once painted. The next step is to im­port a mid-res­o­lu­tion ver­sion of the char­ac­ter model you will be us­ing for the hair. Make sure this geo has its UVS in UDIM 1001. This is im­por­tant be­cause Xgen uses Ptex when paint­ing maps. 03 Cre­ate hair cap geo The next step is to cre­ate cap geo out of the im­ported mid res­o­lu­tion mesh. To do this we will chop ev­ery­thing off the geo that we don’t need hair on. You will cre­ate this geo to gen­er­ate your Xgen hair on in­stead of your clean model. We will make th­ese cap geos in­vis­i­ble at ren­der time or cast shad­ows so they don’t ex­ist to the cam­era by chang­ing their ren­der stats in the at­tribute ed­i­tor. Al­ter­na­tively, you can hide the cap geo com­pletely when ren­der­ing, it doesn’t need to be vis­i­ble for the hair to show up.

The first steps be­fore start­ing the Xgen is to check that your project is set

The next step is to im­port a mid res­o­lu­tion ver­sion of the char­ac­ter model you will be us­ing for the hair

04 Cre­ate curves from proxy geo Now we’ll im­port the proxy geo we cre­ated in Zbrush ear­lier to cre­ate guides from. This is done by se­lect­ing the edges and con­vert­ing them to curves. While do­ing this step it is im­por­tant to keep in mind the di­rec­tion in which your curve is go­ing. The curve needs to start and be touch­ing the base of the scalp or Xgen will cre­ate a real mess when you gen­er­ate the hair and po­ten­tially crash Maya. The lit­tle square rep­re­sents the start of the curve, you can re­verse the di­rec­tion of the curve in the Sur­faces tab > re­verse Curve.

05 Cre­ate Xgen guides We’re go­ing to cre­ate a new Xgen col­lec­tion and de­scrip­tion with the fol­low­ing se­lected: Splines > ran­domly Across Sur­face > plac­ing And Shap­ing Guides. Now that we have curves rep­re­sent­ing the gen­eral vol­ume of the hair from the pre­vi­ous step we’ll con­vert th­ese to Xgen guides.

We will do this by se­lect­ing our curves and nav­i­gat­ing to the Xgen Util­i­ties and us­ing the Curves to Guides op­tion. Af­ter this we’ll need to cre­ate more guides, as evenly spaced as pos­si­ble, to fill in the rest of the head.

06 Paint den­sity mask The next step will be to paint a Ptex map to con­trol where ex­actly we want the hair to grow and how much. The maps are painted in­side Maya with the 3D pain­ter tool. Th­ese will be painted in greyscale, white is more and black is less. You can also paint with grey tones to thin out par­tic­u­lar ar­eas. To start paint­ing you will need to click the Paint­brush icon next to the Mask sec­tion un­der Gen­er­a­tor At­tributes, set your res­o­lu­tion and name it. Then to save your new painted maps, click the Save icon next to the Paint­brush.

07 Paint re­gion map Now we’ll paint a re­gion map to de­fine where the hair will part. With­out the re­gion masks, Xgen will not dis­trib­ute the hair in a nat­u­ral way. This map is also painted in­side Maya, the same way as we painted the den­sity mask. The dif­fer­ence be­tween the two masks is that the re­gion mask is painted in RGB colours in­stead of greyscale. You can find the re­gion map un­der Re­gion Con­trol. If sat­is­fied with your re­gion mask, click the save icon. The re­gion map won’t work un­til you turn the re­gion mask from 0.0 to 1.0.

08 Fine-tune hair Next we’re go­ing to fine-tune our guides by groom­ing th­ese as per our con­cept. At this time, we’ll set the length for each guide, the width and ta­per of the strands, and ad­just the den­sity.

This par­tic­u­lar project has a den­sity of 100, and a width of 0.0105 with a ta­per of 0.2750.

09 Add lay­ered clump­ing This groom re­lies heav­ily on lay­ered clump­ing with Xgen’s Clump Mod­i­fier to cre­ate a nat­u­ral feel­ing to the hair. How we go about do­ing this is by hav­ing three Clump Mod­i­fiers stacked on top of each other. For the first, we will click Setup Maps and se­lect the box guide and save. The next will be set up sim­i­larly ex­cept in­stead of us­ing guides, set the Den­sity to 0.5 and click Gen­er­ate. The next setup is sim­i­lar to the se­cond, ex­cept set the den­sity to an even higher value. You can pre­view each clump­ing layer eas­ily with Color Pre­view.

10 Add noise mod­i­fier Adding noise to your hair can help add more re­al­ism to your groom by adding a no­tion of im­per­fec­tion. This project has a noise with a fre­quency of 1.0 and mag­ni­tude of 0.5 added. You can layer noise as well de­pend­ing on your hair­style or groom but for this style it wasn’t nec­es­sary.

11 Add cut mod­i­fier Us­ing the Cut Mod­i­fier will trim the ends of your hair by a cer­tain length de­fined by you. This can be handy to cre­ate a nat­u­ral look to the tips of the hair. This can be used to de­fine split ends and hair break­age or even freshly trimmed hair.

This hair­style has one cut mod­i­fier added with an amount of: rand(0.5,2.0).

12 Cre­ate stray hairs Cre­at­ing stray hairs is a very sim­ple process with Xgen but it’s very ef­fec­tive for cre­at­ing even more im­per­fec­tion, thus adding more re­al­ism. To do this, nav­i­gate to the de­scrip­tions tab in the Xgen ed­i­tor, then click Set Stray Per­cent­age. Set this value to 4. Now cre­ate a noise mod­i­fier and set the fre­quency to ‘stray() ? .2 : .1’ and the mag­ni­tude to ‘stray() ? 7 : .4’. All of th­ese num­bers can be ad­justed based on your spe­cific hair­style or groom but the ex­pres­sion will stay the same.

13 Cre­ate fly­away/windswept hairs This step is mainly for cre­at­ing the art directed and windswept hairs seen in the con­cept. To do this we cre­ate a new de­scrip­tion within the same col­lec­tion us­ing the op­tions Splines>at Spe­cific Points>plac­ing and Shap­ing Guides. Add a Clump Mod­i­fier and set up the maps to fol­low guides again.

Adding noise to your hair can help add more re­al­ism to your groom by adding a no­tion of im­per­fec­tion

14 Set up Arnold shaders for hair Now we will set up our Arnold shaders for the hair. To as­sign the shader, se­lect the de­scrip­tion group in the out­liner and then as­sign the AI Stan­dard Hair Shader in the Hy­per­shade. Af­ter this is done, to cre­ate the dyed white hair and nat­u­ral brown roots we will use ramps into the Me­lanin, Dif­fuse and Spec­u­lar. Adding more me­lanin will make the hair darker so this is ramped to a 0.8 value. We want the white dyed hair to have more dif­fuse val­ues so this is ramped to white. The spec­u­lar was also tinted slightly browner near the roots.

15 Add fi­nal touches Now is a time you can look over your groom as a whole once it’s ren­dered and make tweaks as nec­es­sary. You can in­crease your stray hair per­cent­age and ad­just your mod­i­fier val­ues if they don’t look right.

This is the time to make sure ev­ery­thing is work­ing co­he­sively and ad­just the el­e­ments that may be fight­ing each other.

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