Creating a Medium-Length Hairstyle for a Woman in Houdini

Introduction

Hi everyone! My name is Artem, I'm 31 years old and I'm currently working as a Grooming Artist on a freelance basis. I work on creating various character hairstyles for commercial cinematics, animated commercials, entertainment TV shows, movies, and projects with various digital doubles.

I started my introduction to CG in 2018 when I got a job in a company as an Exterior Visualizer and ran 3ds Max on my work PC for the first time.

After a year of work, I realized that visualizing industrial models and exteriors was too boring for me. I decided to explore something new, in a different direction. During that period of time, I came across Andrew "Charly" Krivulya's YouTube channel. He was creating incredible and complex hairstyles while sharing hair tutorials. I got really interested in it and decided to try to do something similar.

That's how I was introduced to Ornatrix, is a tool for creating digital hair and fur. I'm still working in this plugin as I find it intuitive and easy enough to work with, you can create incredible hairstyles for your characters with it.

A huge advantage is that Ornatrix exists for Maya as well as for 3ds Max, Cinema 4D, and even Unreal Engine 5, which gives it a great advantage over other plugins. I have tried other tools, such as XGen and Yeti, and they are good in their way, but I opted for Ornatrix in Maya.

Creating Hair in Houdini

As of late, I decided to try out the Houdini hairstyling tool as I believe it is a tool with endless possibilities. I would be remiss if I didn't try working in it. I've seen cool artists post incredible projects on ArtStation with hairstyles done in Houdini and I've made it my goal to do something similar someday!

I want to clarify that by the time I decided to make this hairstyle in Houdini, it was my second experience creating hairstyles there, and I had two weeks of experience with Houdini in general. I decided to compare the process of creating hairstyles in Ornatrix and Houdini and figure out where it would be faster and easier to create the same hairstyle.

I didn't use too many references to work with as I already had an idea of what I wanted to get. I chose a few photos from the Internet to capture the general shape of the hairstyle, and I also found some photos with details such as the hair parting place and "baby hair." Of course, if you have a set of photos of the actual hairstyle from different angles, it's better to use them as they will help you in your work and speed up the hair creation process.

So after I collected the references, I imported the head model into Houdini. Then I subdivided the mesh and started painting the hair Density Mask using Attribute Paint. This is very convenient to do in Houdini as you always have the possibility to switch quickly between masks, mirror masks (instead of painting the whole thing), add blur or multiply/fold/subtract masks between each other.

You should also create a VDB of the head meshes so that you can use it later without encountering problems with guides/hair penetrating the head.

After I drew the preliminary hair Density Mask, I proceeded to create the guides. I grew each guide separately so I deleted all the guides created by Houdini automatically. Using the Guide Groom node (analogous to Edit Guides in Ornatrix) and the Draw brush, I draw the initial overall shape of the guides and then used the Sculpt brush to comb these guides using references for help.

I don't fill the surface of the head with guides too tightly. I usually do a lot of guides where the shape of the hairstyle changes a lot and I need to be sure to replicate it. When I've done the total amount of guides, I add a few more Guide Groom nodes where I incorporate intermediate guides. For this, I use the Plant brush, which is perfect for this task (interpolation between the guides takes place and you practically don't need to comb the resulting guide).

I've noticed that in Houdini, you need more guides for normal hair interpolation than in Ornatrix. I think in Ornatrix, I could have used half as many guides.

After I've made the basic shape of the guides, I gradually start creating the hair. To do this, I use the Hair Generate node and first use the Hair Clump node to bundle the hair. I plug the guides into the correct input so that the bundling occurs on them.

I go back and draw a new mask for the Hair Clump node to remove the areas where I don't want to have a clump area, such as the temple area. Then, I add another Hair Clump node, but with smaller bunches.

In the next step, I incorporate a few Frizz nodes with different frequency settings, followed by another Clump node. Additionally, I create several Guide Mask nodes to select a random set of individual hairs to which I will later apply other Frizz and Bend nodes for added realism. For the tips of the hair, I also include the Bend node with a range of bend angles. Toward the end, I introduce the Set Length node and randomize the hair length within a range of 0.9 to 1.05, providing a greater sense of realism.

To create "Baby Hair" I use a similar approach.

Rendering

For rendering, I use Maya with Arnold. I work in it as the shader setup is quite simple. I can do various experiments with the hair shader and render it quickly.

I unload the hair as "alembic" from Houdini and import it into Maya as Ornatrix Alembic. I do it this way because it's easier for me to work and customize with such an object, I can disable most of the hair in the viewport and leave 100% on the render.

For lighting, I used a studio HDRI Map + some rectangle lights to emphasize certain areas of the face and hair.

For this work, I used VFace textures from XYZ Texturing as it is very convenient and easy to work with. I transferred the textures to my mesh using WRAP from R3DS. I finalized the albedo in Substance 3D Painter and created roughness there using the Utilities map. I transferred Displacement to my model and made some final adjustments in ZBrush. Then I proceeded to bake a new Displacement. After customizing the skin material, I began customizing the hair.

In the hair shader, I use several nodes. First, I employ the Ramp node to darken the roots of the hair, as I find it enhances realism. Next, I incorporate the aiColorJitter node to add variation to the base color. When working with blonde hair, I use a low melanin value, as increasing this value darkens the hair. If I aim to achieve a PBR hair shader, I avoid using diffuse color and solely rely on the base color.

Final Words And Tips For Artists

To summarize this work, when comparing the process of creating hair in Houdini and Ornatrix (using a simple hairstyle as an example), I don't notice any significant differences. The pipeline is 90% similar, with only minor variations. However, I anticipate noticing differences when working on more complex hairstyles such as curly heads or braids, but that's a story for another time.

Lastly, I would like to advise artists who want to explore grooming not to hesitate to experiment with the hair creation process and try different techniques and software programs.

Frankly speaking, it doesn't matter which software you use, as any of them will allow you to create whatever you want. Begin with simpler hairstyles to grasp the fundamentals of creating guides and building hair from them. Remember to use references, as they provide valuable information for your project. More practice and you will succeed!

My YouTube channel with short tutorials on Ornatrix is here. CharlyTutors channel with lots of tutorials on Ornatrix that can help you. Here is HadiKarimi's channel with interesting lessons on creating hairstyles in XGen. The last one is Yuriy Dulich's channel with interesting lessons on working in Yeti: click here. 

Artem Erikenov, Grooming Artist

Interview conducted by Theodore McKenzie