Sculpt realistic anatomy in ZBrush

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If you want to go further than just using free 3D models and learn how to sculpt realistic anatomy in ZBrush, this is the tutorial for you.

As you will see, ZBrush is an amazing tool for a project like this because it provides you with the much-needed freedom required when shaping forms.

Download the files you'll need for this tutorial.

01. Look for references

Make sure you have enough reference material before starting

If you're going for a full body anatomy study like I am, then make sure you have enough reference material for each part. You can find some 360-degree pictures of a model in various poses here. In addition, Google and Pinterest are great resources to search for images. 

I decided on Michael Phelps because of his well-defined muscle structure, the huge amount of reference material available and his unusual body proportions.

02. Check body proportions

Use your character's head to get its proportions right

Probably the most important thing in any kind of art – whether you draw, sculpt or paint – is the proportions. It doesn't matter how much attention you pay to detail, rendering and composition, it will all be meaningless work if your character doesn't  look real. 

The easiest way to measure a character is with ‘heads'. This is why I always start by getting my base shape for the face and using the Transpose tool to measure 7.5/8 heads for my character. 

Of course, you need to be aware that there is always an exception. For example, with Michael Phelps, his torso is longer, he has shorter legs and his arm span is bigger than the average person. 

The steps below explain how to measure your character in ‘heads' using ZBrush:

• Once you have finished shaping your base head, turn off perspective (by pressing the P key), select the Transpose tool and draw out a line from the top of the head to the bottom of the chin holding Shift. This will ensure that it's straight.
• In the top menu, go to Preferences > Transpose Units, set Minor Ticks to 0 and Calibration Distance to 1.
• Now if you draw a line from the top to the bottom of the character, you will see that it's divided by heads.

03. Make ZBrush body base mesh

Alternatively, just use ZBrush's base mesh

To get an easier start, you can always use the base mesh that comes with ZBrush, if you're not feeling too confident with your knowledge of proportions. The base mesh comes with the Skull SubTool, so you can always take a look at how it's built.

I don't want to spend a lot of time on proportions, so this time I will use the base mesh. To load the base mesh, do the following:

• Select Lightbox
• Click on the Tool sub palette
• Find and double click on Nickz_humanMale
• Drag it out with the left mouse button on the viewport and click Edit Object (or press T on the keyboard).

04. Make adjustments to the base mesh

Use Transpose Master to adjust your character's pose

I don't find the initial pose of the base mesh appealing, so I will change it using the Transpose Master plugin, and give it a more natural silhouette. Transpose Master combines the lowest resolution of all SubTools and creates a mesh that you can pose together. The pose can then be transferred back to the original SubTools. To use the Transpose Master, work through the following steps:

• Go to Zplugin > Transpose Master and click on TPoseMesh.
• Pose your model by masking out the parts that you want to move, by holding Ctrl to mask and inverting the mask by holding Ctrl+LMB on the viewport.
• Once you've finished with the posing, go back to Zplugin > Transpose Master and click on TPose > SubT.
• Your changes will now be transferred to your original model.

While posing your model, you can always export your pose by selecting TPoseMesh. You can then load it manually by going to the scene with your original model and selecting TPose > SubT.

05. Paint body bone landmarks 

Paint skeleton landmarks to keep track of shapes and proportions

Before I start the sculpting process, I do my best to paint all the skeleton landmarks that are seen on the human body. It allows me to keep a better track of the shapes and proportions. You can paint on your model in ZBrush by following these steps:

• Firstly, fill it with white colour by selecting white on your palette on the left, going to Colour in the top menu and selecting Fill Object. Make sure that your RGB Channel is turned on.
• Select your Standard brush and uncheck the ZADD above the Intensity slider, while keeping RGB turned on. This will ensure your Standard brush only paints the desired colour, without impacting on the surface of the mesh.
• Pick the colour that suits you and start painting your model.

The main landmarks that I usually paint are the sternum, costal cartilage, iliac crest, vertebrae, anterior superior iliac spine, curve of tibia, clavicle, scapula, acromion process, zygomatic bone, mandible and the temporal line.

06. Use subdivisions

The powerful part of using the base mesh is having the correct topology on your body from the very beginning. This allows you to use subdivision levels in ZBrush, which increases the polygon count of a model by replacing each polygon with multiple polygons – the higher it is the more detail you can add. In addition, you can always come back to your first subdivision level and adjust shapes, and this change will be reflected when you come back to the highest subdivision. Let's look at an example of how this works:

• I know that I'm going to sculpt details like veins, skin stretching and so forth on the highest subdivision, as it will give me millions of polygons to work with.
• In case I want to change the bulkiness of his chest, I can always go back to a lower subdivision and add some volume to it. All the detail I added on the highest subdivision won't be visible on the lower one, but it will still be there when I come back to the highest level.

07. Block out shapes

Throughout my whole sculpting process, I only use a few brushes: Standard, Dam_Standard, Clay Buildup, Clay, Smooth and Move.

I am not concerned about the likeness at this time; for now I want to focus on getting all the muscles blocked-in with the correct shape and placement. I use Clay Buildup and Smooth to get the shape, by adding clay and smoothing it out until I get what I want. I try to maintain as low a subdivision level as I can. I go higher once I don't have enough polygons for the shapes I want to add.

08. Add muscle volume 

Turn off symmetry before building up the body

I give my model some more subdivisions and start adding volume by using the Clay Buildup and Clay brush on very low intensity settings, going slowly and not overdoing it. 

At this stage I stop using symmetry, because I want to be as close to realistic filling as I can. I have noticed that I get the best results when I turn it off early. In addition, I use Transpose Master (like in step 04) to bend the fingers.

Make sure that you are not focused on one part of the body all the time – jump between them. This will make you see your sculpture as a whole. Also pay attention to your references, as they play an important role at this stage.

Next page: 5 more steps for sculpting realistic anatomy in ZBrush

09. Exaggerate features

Focus on your character's defining features

Sculpting likeness is the hardest task to perform in ZBrush, but also the most rewarding if you manage to do it. However, you don't have to make it perfect, unless you plan to do some close-up renders.

Search for the features that define the person. So for Phelps, it's the length of his face, narrow jaw, big orbicularis oris muscle and protruding ears. 

To help me find these, I look at the work of caricature artists, because they always exaggerate the characteristics of the face.  

10. Create clothing

Find plenty of references to help make realistic clothing

As always, the first thing you need to sculpt believable cloth is reference. Luckily for me there is no shortage of images of Michael Phelps wearing speedos on the internet. The extraction method is a good choice for creating clothing that sticks to the body.

To extract a new mesh:

• Hold Ctrl to paint the mask onto your model. Remember that the new mesh will extract in the same place as your mask.
• Once you're happy with the shape, go to SubTool > Extract and turn off Double, otherwise you will get an extraction on both sides of the mesh. Set your Thickness to 0.001 and click Extract.
• You should see a preview of the mesh that will be generated. Click Accept to create it and it will then appear in your SubTool list.
• Initially, the middle of the mesh is going to be masked. Use your Smooth brush to make the edges even.

To gain better control of the mesh, I use ZRemesher to achieve proper topology by doing the following:

• Go to Geometry > ZRemesher.
• Lower the Target Polygon Count to 0.1/0.2 and click ZRemesher (make sure that your symmetry [X] is turned on for that process).
• Now you have a mesh that you can easily manipulate and position however you like. Once you're done moving it, you can always use ZRemesher again in order to fix the topology.

The final step before sculpting is to give it some thickness:

• Go to Geometry > Edge Loop.
• Lower Loops to 1, set Bevel to 0 and experiment with thickness. It is best to roughly match the thickness of material that you're planning to sculpt.

When the mesh is ready to sculpt, I use the Standard brush with Alpha 37/38/39 to get some nice results with the wrinkles. Don't subdivide your mesh too high – do it step by step. The swimming cap will be done the same way. 

11. Pose your model

An asymmetric pose will make your work look more interesting

Your work will always look a lot more interesting when you break the symmetry even more by changing pose for the final render. I have an interesting pose in my reference folder, so I will try to get something similar – again by using Transpose Master. 

In this case, the rotation of the head and torso, combined with the head tilting upwards, gave an interesting result. Remember that we always have to adjust the anatomy after posing. I need to make his neck muscle more pronounced on one side.

12. Export the model

Decimate your model before exporting it

Before exporting models to 3D applications like Maya or 3ds Max, I need to ensure I will be able to use them. Unfortunately, when working on a mesh that has a few million polygons, this might not be possible.  

I will use the Decimation Master plugin to lower the polycount on the mesh and preserve all the high poly detail. To decimate your model, follow these steps:

• On the top menu, go to ZPlugin > Decimation Master.
• Click on Pre-Process All – this will recalculate all the information about all the SubTools.
• Once complete, select your desired percentage of decimation. For me, 20 per cent usually works perfectly. Next, click Decimate All and you will notice a huge drop in the number of polygons – but your detail shouldn't change.
• Select Export All SubTools. Now you can export everything as a single .obj file to use in Maya.

13. Move into V-ray 

The final step is to import and render your model in V-Ray. I bought premade V-Ray scenes from flippednormals.com and want to make use of them when rendering Michael Phelps. After the purchase you can download everything you need from the website, including a video tutorial on how to set everything up. The wealth of material may seem overwhelming at first, but it won't take you more than five minutes to get a great looking render.

This article originally appeared in 3D World issue 217; Subscribe here!

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