Sculpting and Grooming a Humanoid Cat Character with ZBrush and XGen

Introduction

I'm Nathalie Appert, a 3D Character Artist specializing in texturing, look dev, and grooming. I recently graduated from Think Tank Training Centre's CG Asset Creation program. I have a BFA in Photography from New York University. I wanted to work as an architecture and real estate photographer, but I had difficulties finding clients.

I thought I should add to my skillset to stand out from other photographers, so I tried 3D modeling for virtual home staging. I ended up enjoying 3D a lot more than I expected, and after a couple of years of teaching myself Blender and Substance 3D Painter, I decided to do a full career switch and join Think Tank to consolidate my skills and specialize in character creation for film.

During my time at Think Tank, I worked on four projects, one per term. My first project was a 3D recreation of an illustration by Simz. The second one was Tamara, a simple character created in 6 weeks to get familiar with the full character pipeline. The third one was The Moth Breeder, a full character where I focused on hand-painted textures and learned grooming with XGen. The fourth and latest project is Rhein Noc.

Rhein Noc

For our projects at Think Tank, we often have to search for concepts to recreate in 3D. During my intermediate term, I came across this concept by Rynir that I found really cute. At the time, it was still too complex for me as I did not know how to create hair and fur.

However, it kept a special place among the hundred other concepts that I had saved. After I learned to use XGen for The Moth Breeder and enjoyed the process, I decided it was finally time to work on Rynir's concept.

My initial goal was to create a portfolio project that I could be truly proud of, something that I believe could fit in a movie or show. I wanted to create a character that would've inspired me to work hard on my craft two years ago, something that I would've been so impressed by that I would think, "There's no way I can get to that level."

I wanted to prove my past self wrong, that it's possible to get there with dedication. My Think Tank classmates and alumni were my biggest inspiration. Ember Pettersen, Sriram Venkatesh, and Hemant Kunj are just a few whose work inspired me from day one of joining the school. I wanted to create a groom-focused project because I believe the groom and look dev of a project really makes a difference in the final look.

Too often, I have seen great modeling or sculpting that loses appeal because of bad texturing or rendering. I wanted to show my skills at both creating fur and a hairstyle. Here is some work that inspired me and that I used as a reference throughout my project.

Modeling

The trickiest part about modeling was getting the proportions correct and creating a harmonious mix between human and animal features. To save time on sculpting, since it was not the main focus of this project, I started with my body mesh from my previous project, The Moth Breeder, and made adjustments to fit the proportions of a young teenager.

I like to retopologize in Maya early on, soon after my blockout stage, when I have my primary forms set. It makes it a lot easier for me to sculpt in ZBrush on good topology, and I can always adjust it later.

I spent most of my time refining my secondary shapes for the body and did not go too in-depth into tertiary shapes, like skin and muscle details, since most of it would be covered by fur. For the head, Tony Camehl's sphynx study came in useful, as it laid down cat proportions in a way that I could easily compare to human proportions, for which I used Anatomy for Sculptors.

I would have both cat and human references side by side and decide which way I wanted to lean toward and how to match the concept as well. At this stage, there is no magic recipe to get the perfect mix. It's a lot of iterating, going back and forth between versions, and working on other parts of the model to come back later with a new eye. Even when I was satisfied with the face in A-pose, I had to make more adjustments after he was posed.

At the start of the project, I decided that the final showcase of my character would only be posed, so I would not have to worry about hair simulation, and I would only have to create one version of the groom.

This also meant that I only started modeling the clothes and accessories after I posed my character. I used Marvelous Designer for the shirt, the pants, and the armband cloth, which I then brought into ZBrush for some shape and fold adjustments.

The belt, the pouches, the sheath, the sword, and all the smaller accessories were modeled in Maya first. Just like with the body, I like to work on good topology when I'm sculpting in ZBrush, so I always prefer to model my low poly in Maya. This way, I also don't have to do any retopology.

The concept had a lot of rope and string elements, which I created with curves that I turned into geo using Maya's sweep mesh plug-in. To create the stitches on the belt, the pouches, and the armband, I used MASH in Maya to distribute them and placed them using curve wrap.

I did my UVs in Maya after modeling and before bringing the models to ZBrush. I find it useful to have UVs mapped out early on, since it avoids having to copy and paste them in ZBrush, and it's a convenient way to transfer attributes in Maya. For the body, I unwrapped the model while it was still in A-pose so I could have mirrored UVs for the limbs.

It then makes it possible to texture symmetrically in Mari with a posed model. Once I finished sculpting, it was time for the groom. I divided my body into different scalps, since the fur on each part would look different and have its own description in XGen.

I wanted the body hair to look interesting and not just follow one direction. I gathered multiple references from different angles and drew over the hair flow in Photoshop. Where the anatomy was human, like the arms, the chest, and the top of the hands and feet, I followed references of human body hair. Where the features were more cat-like, such as the face and around the paw pads, I used animal references. 

To have a better idea of how the flow would work on my model, I drew directly on it in ZBrush with polypaint. This made it easy to erase and adjust the flow without having to deal with guides yet, especially since things can easily go wrong or crash in XGen. The more planning you can do before using XGen, the better.

After I finished drawing in ZBrush, I exported the polypaint as a texture so I could use it in Maya to draw my guides. I followed Omar Hesham's technique to draw curves that I would then convert into guides.

For the ears, I did not plan the flow in ZBrush and instead just drew it over a screencap of my model. I decided to divide the ears into three descriptions: one for the back of the ears and the edges, a second for the short hair inside the ears, and a third for the long, clumpier hair in front of the ears.

For the head hair, finding references was a bit trickier since the hairstyle in the concept isn't realistic. I decided to use the short shag and wolf cut hairstyles as main references. I improvised a bit more for the pigtails and styled them based on a mix of real pigtails, wigs, and tassels.

The tail was probably the most challenging for me. I was trying to have the clumps from the concept, but still have the soft and fluffy feel from my cat references.

Texturing

I textured the model in Mari using nodes. I kept the body texturing simple because most of it was covered by fur. The nose, the paw pads, and the claws were some of the uncovered spots with added details. I also painted some veins on the ears that would show through with subsurface scattering, although that was just more for fun since I knew it wouldn't show in the final render.

The eyes were first created in Photoshop by using multiple macro photographs of cat eyes, most of them by Andrew Marttila. I then projected the black and white mask in Mari and added color variations. To keep my character cute and stylized, I kept the sclera simple and only painted a hint of red for the veins.

For the clothes and accessories, I would usually begin with a tiled texture, driving my base colors. I then add color variation and hand-paint any unique pattern. Finally, I add wear in strategic places using Ambient Occlusion and Curvature maps, or by hand-painting it. In Mari, I usually work one channel at a time. Once I finish my base color, I move on to the Roughness and Bump. I reuse nodes from my Base Color or create new ones if applicable.

I like to finish all channels first before testing the textures in VRay for the first time. That way, I have a base that I can work from, I take notes on what needs to be adjusted, and go back to Mari to rework the textures. I go back and forth between Mari and VRay until I'm satisfied with the result.

Lighting and Rendering

For the lighting, I have an HDRI supported by an orange back light, a blue fill light, and a key light on the face. I also have an HDRI and two lights linked to the background only.

I used V-Ray to render my shots. The groom was the heaviest aspect to render, and I had to lower the density of the tail because of excessive render times. At the end, it took between 15 and 45 minutes per frame to render my reel. Without a render farm, I had to let my PC render for two weeks straight for a minute-long reel.

Through lighting and look dev, I usually try to get my raw renders to look as close to the final look that I want. I use Nuke for small adjustments I need to do post-production. For this project, I did not do any complex compositing. I mostly corrected and graded some areas. I had prepared some maps beforehand to add in my render elements to easily select the fur areas I wanted to adjust, such as the eyebrows and the eye marks.

Conclusion

Like with a lot of my other projects, the main challenge is to trust the process. The first days of modeling, grooming, or texturing can be frustrating because it doesn't look great immediately. It takes patience and perseverance to keep pushing your work to reach a satisfying point.

This brings me to my advice for beginners, that it's ok to take your time. I used to compare myself to speed sculpt videos and think I had to create a portfolio piece in a week. Learning 3D art might feel slow in the moment, but if you use your time efficiently and practice consistently, you'll look back on your work and think you progressed and improved quickly.

With this project, I got to learn about animal anatomy and fur. I'm looking forward to working on a full animal eventually, to push those skills even further. Now I'm looking for job opportunities as a Texturing and Grooming Artist in Europe, but in the meantime, I will keep honing my texturing and grooming skills. I plan to learn Substance 3D Designer, and I want to learn grooming in Houdini, since it is commonly used in studios.

Thank you, Emma and 80 Level, for reaching out and giving me this opportunity to write about my project. Thank you to everyone who read this interview. I'm fortunate to be able to share this passion project with you, and I hope I was able to inspire some of you. Come say hi on ArtStation, Instagram, and LinkedIn!

Nathalie Appert, 3D Character Artist

Interview conducted by Emma Collins

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