Our thanks to Scott Eaton for this tutorial. For more of his excellent work, head to www.scott-eaton.com.
This tutorial first appeared in issue 81 of 3D Artist.
This tutorial walks you through the steps of blocking in an écorché study of the face in ZBrush.
Écorché is the age-old practice of sculpting or drawing the body without skin in order to study the forms of the underlying anatomy. Here we build up the main anatomical forms of the face and discuss their importance to portraiture.
Sculpting or drawing a face is one of the most challenging things an artist can attempt. Most artists wander in the dark when creating a portrait – placing planes and locating features based only on observation and experience. With lots of practice this can lead to good results, but everyone can benefit from a road map that helps them work faster and better.
Knowledge of facial anatomy is just that – a guide to the forms and regions of the face. The face, like the body, is a puzzle of interconnected anatomical pieces. Once the artist learns common shapes and connections he can quickly block in a likeness.
The goal of this tutorial is to familiarise you with these common anatomical structures.
Step 1 – Fit the skull
We first need to get the skull to fit the volume of the reference portrait supplied. Turn on transparency and adjust the proportions with a large Move brush. The areas of the skull that should be superficial (ie near the surface) are the eye orbits, the zygomatic arch (cheek bone), bridge of the nose and forehead. The rest of the skull has muscle, fat or cartilage between it and the surface. It is important to appreciate where the skull is closest to the surface so we can use these as landmarks when constructing a portrait.
Step 2 – Place the masseter
The masseter is the first of two skeletal muscles that we need to place. Skeletal muscles connect bone to bone and articulate a joint (as opposed to facial muscles which articulate the skin to create expression). In this case we are connecting the mandible (jaw) to the zygomatic arch. The masseter creates significant surface form on the face and needs to be located correctly. In ZBrush, block in the shape with your preferred geometry creation method, then subdivide and detail.
Step 3 – Understand the temporalis
The temporalis is our second muscle of mastication (chewing). This muscle combined with the masseter, give humans a wider range of motion for biting and chewing. The temporalis is a large, distributed fan-shaped muscle that anchors to the skull along a crescent (the temporal line) that stretches from the upper-lateral corner of the orbit back to behind the ear. This distributed muscle body converges, focusing its power, and passes behind the zygomatic arch, grabbing onto the anterior point of the mandible called the coronoid process.
Step 4 – Construct the nose cartilage
The nose exhibits an amazing amount of variation in life. It is important to understand that despite this variety, all noses are built from the same three pieces of cartilage and a small bit of fat. The septal cartilage establishes the midline of the nose. The complex shape of the alar cartilage creates the ball of the nose, and the lateral cartilage creates the side walls of the nose. Finally to funnel in the air we have a wedge of fat that creates the nostril of the nose. Using your best construction skills, construct this geometry over the nasal opening of the skull.
Step 5 – Place the eyeball
An adult human eyeball is approximately 24mm in diameter, there is small variation in this but it is a very useful average. The most common mistake in people’s portraits (in CG anyways), is that they always make the eyeball too large, wedging a grapefruit into the orbit and then trying to get the eyelids to fit properly. Here, with a correctly sized sphere (do it visually as our skull is not to scale) centre the eye in the orbit, and move it forward to the point where the bone of the orbit still protects it.
Step 6 – Make eyelids using tarsal plates
The eyelids have two stiff plates of cartilage in them called tarsal plates. These form the foundation of the lids and are anchored to the orbits by something called the canthal ligaments. The medial (inner) canthal ligament is visible on the surface and so creates important surface form, the lateral one attached inside the rim of the orbit and is not visible. Paint a mask on the eyeball and then use Subtool>Extract to make your tarsal plates. Use your favourite geometry creation method to place the ligaments, then DynaMesh the result together.
Step 7 – Construct orbital fat
With the eye and lids in place you can see the large cavity we need to fill with orbital fat. Orbital fat is packed all the way into the orbit and is what cushions and holds our eyeball in place. With age we can see this fat pushing out of the orbit, giving us characteristic bags under our eyes. Construct half a donut of fat and locate it in the space between the tarsal plates and the rim of the orbit.
Step 8 – Put in the oribicularis oris
Our lip/mouth muscle is the first of two orbicular (circular) muscles on our face, made of concentric rings of muscle fibres, which pull inward in various combinations to make a variety of lip shapes and phonemes. The muscle is extremely complex as many surrounding muscles will
pass fibres into it. Here we show the deep cheek muscle, the buccinator, merging into the orbicularis oris from the sides. The buccinator originates above and below the molars and passes fibres into the deep section of the orbicular muscle.
Step 9 – Make deep cheek fat pads
There are a couple of fat pads in the deep recesses of the skull that act as cushions for the facial muscles. These deep cheek fat pads sit over the buccinator and squish out into the depression in front of the zygomatic bone and a bit above the zygomatic arch. The volume of these fat pads determine the size of the hollow in a person’s cheek. The man in this portrait has very hollow cheeks so keep the volume small as you construct these fat pads.
Step 10 – Cut oribicularis oculii
The face’s second orbicular muscle covers the orbit and eyelids and is responsible for blinking, squinting and raising the cheek. It extends quite far over the orbital rim and wraps medially to attach to the medial canthal ligament. Here we have cut away the medial half of the muscle to keep the orbital fat and tarsal plate exposed. Use ZSpheres or an IMM Curve brush to get geometry wrapping around the orbit, then flatten it and DynaMesh it. Use the TrimRectangle tool to cut off the medial half.
Step 11 – Build forehead muscles: temporalis and corrugator
These two muscles are important contributors to the expressions of surprise, anger and sadness. They are thin muscles so they don’t create surface form but we certainly recognise the expressions they create. For the temporalis, create a flat sheet of geometry from just above the orbit to the top of the forehead. Medially it stretches almost to the centre, laterally to the temporal line. The corrugator is a small diagonal muscle that spans the space between the base of the nose to a point approximately mid-eyebrow. Place this using a small piece of geometry.
Step 12 – Lift the lip
The human face has a network of muscles that articulate the upper lip. The muscles anchor into the upper edge of the orbicularis oris muscle (as well as intermingling fibres into the lip). They are called (from left to right): levator labii superioris alaque nasi, levator labii superioris and zygomatic minor. They are respectively responsible for wrinkling our nose, sneering and subtly deepening the nasolabial furrow (the furrow that comes off the nose and proceeds down by the corner of the mouth). Construct these like little pieces of linguini. Note: there is also a sneaky corner-lifting muscle not shown here.
Step 13 – Construct the zygomatic major
The muscle, zygomatic major, is our smile muscle. It can be difficult drawing or sculpting a smile but once you understand the origin/insertion and action of this muscle, the construction of the smile becomes easy. Build this muscle from the corner of the mouth out to the lateral surface of the zygomatic arch. It has the widest pull of any of our facial muscles and lifts and stretches the lips when it activates, creating a big smile.
Step 14 – Pull down corners
Just as we had zygomatic major pulling the corner of the mouth upwards to create a smile, we have a corner depressor called depressor angulii oris, that pulls the corner down to create a frown. This muscle pulls on the corner of the mouth but also passes fibres into the upper part of orbicularis oris. Some of this form can be visible on people’s faces. A second small, but related, risorius muscle pulls the mouth wide and slightly downward. Unusually, it originates from the skin over the masseter.
Step 15 – Depress the lip and lift the chin
The opposite of the upper lip lifters (Step 12) is the lower lip depressor, depressor labii inferioris. It anchors onto the jaw just inside the depressor anguli (Step 14) and then ascends, grabbing onto most of the body of the lower lip. This flat sheet of muscle retracts your lower lip showing your bottom teeth. Adjacent to this muscle is the last muscle of the tutorial: the mentalis. This funny little muscle anchors between the lower teeth and chin, and grabs onto the fat pad that covers the chin, raising it when activated. It is shown cut away here.
Step 16 – Construct the malar and midcheek fat
Now that the muscles of expression are in place we need to cover them with subcutaneous fat. We have a critical fat pad, called the malar fat pad, that is located below the bottom of the orbit and lateral to the base of the nose. It helps create the nasolabial furrow. As we age it sags and separates from the other subcutaneous fat deposits. Here we also construct the triangular mid-cheek fat pad, also quite defined on our model.
Step 17 – Build the submental fat and jowls
The last few characteristic fat deposits are located on the lower face and under the chin. The submental fat compartment, our double chin fat, is constructed underneath the chin. Be careful not to extend it out too far to the sides, nor too low. Adjacent to this are a pair of jowl fat compartments, one above and one below the jawline. Construct these like small parcels of fat that gravity has had its way with over time.