Chapter 1 – Planes of the head and feature placement

Chapter 1: Planes of the Head & Feature Placement

Created by Sarah Choi (prompt writer using ChatGPT)

Planes of the Head & Feature Placement

For character concept artists across concepting and production. Focus: craniofacial structure, features, emotions.

1) Why Planes Matter

Understanding head planes converts organic complexity into manageable geometry. Planes:

Give you consistent proportions at any angle.
Provide clear lighting logic for reads at thumbnail, gameplay, and marketing scales.
Bridge concept and production: good planar design survives retopo, rigging, and LODs.

Think of the skull as a load‑bearing form (cranium) wrapped with soft‑tissue modifiers (fat pads, muscles, cartilage). Planes are where form turns—places light and shadow make decisions. Designing faces is deciding where those turns live and how sharp they are.

2) Primary Masses & Axes

Before features, block in the head as two coupled volumes:

Cranial mass (neurocranium): an egg tilted back. Greatest width ≈ zygomatic arches.
Facial wedge (viscerocranium): a tapered block projecting frontward for orbits, nose, and maxilla.

Establish the three orientation axes:

Pitch (nod up/down)
Yaw (turn left/right)
Roll (tilt ear‑to‑shoulder)

Mark a center line across the facial wedge to track symmetry through perspective. Then mark a brow line and base‑of‑nose line wrapping around the head as elliptical bands—these enforce perspective and prevent drifting features.

Production note: Maintaining clean axes makes later orthos, blendshape targets, and camera tests predictable. Annotate axes on callouts.

3) Proportional Systems That Travel

Use proportions as check tools, not cages—stylize after you can hit neutral:

Rule of Thirds (profile height): hairline → brow → base of nose → chin roughly equal thirds (hairline shifts with age/ethnicity/style).
Rule of Fifths (frontal width): five eye widths across the face: ear side‑planes | eye | nose bridge | eye | ear side‑planes. In practice, nose bridge ≈ an eye‑width.
Cranial unit: use the distance from brow to bottom of nose as a yardstick to place mouth and chin in perspective.
Ear anchors: top of ear ≈ brow line; bottom ≈ base of nose when head is neutral (pitch alters this in perspective).

Concepting tip: Snapshot “neutral schema” for your project bible—then note permitted deltas for stylization tiers (realistic, semi‑real, stylized).

4) The Planar Map (Front, ¾, and Profile)

Think like a low‑poly sculpt. Start with macro planes, then transition planes, then micro planes for character.

4.1 Macro Planes

Forehead: three steps—(1) frontal plane, (2) angled superior‑lateral planes up to the temporal line, (3) top plane. The brow ridge creates a break.
Cheek mass (zygoma): a bold lateral plane that catches rim light in ¾—key for gender/age/fitness reads.
Nasal block: a prism: dorsum (top), lateral walls, and underside (columella + alar base). Tip shape lives on the underside plane in most light setups.
Mouth cylinder: wrap a cylinder around the dental arcade; the lips sit on this. Upper lip faces down and forward; lower lip faces up and forward.
Chin & jaw: chin is a forward wedge with a flat underside; jaw has a strong ramus (vertical) and body (horizontal) meeting at the gonion—a crisp turn.
Side/head: the parietal/temporal region is a big side plane. Keep it planar to stage ears and hair silhouette.

4.2 Transition Planes (form softness)

Glabella → nasion: soft saddle; hardens with age or low body fat.
Infraorbital step: from lower eyelid to cheek. Avoid a single curve—use a bevel.
Nasolabial bevel: from alar wing to corner of mouth.
Masseter pad: from zygomatic arch down to jaw angle; thickens on clench.

4.3 Micro Planes (character cues)

Lips have three planes each: vermilion front, top/bottom bevels. Cupid’s bow forms two tiny roof planes.
Eyelids: tarsal plate gives the upper lid a roof plane; the lower lid is a shelf plane (never a line).
Brow hairs sit atop a bony bevel—don’t paint brows as stickers; model the under‑plane in paint.

5) Landmark Anatomy for Placement

Name what you place. Key bony and cartilaginous anchor points you can reliably find:

Glabella (brow midline), supraorbital rim, zygomatic arch, zygoma malar point, nasion (between brows), rhinion (where bone meets cartilage), alar base (nostril wings), philtrum peaks, cheilion (mouth corners), pogonion/menton (chin forward/lowest points), gonion (jaw corner), tragus (ear front), mastoid (behind ear).

These are your measurement nails—hang features on them.

6) Feature Placement & Form Logic

6.1 Eyes & Orbits

Think spherical eyeball inside a box (orbit). Lids wrap the sphere and hinge into the brow and cheek planes.
Upper lid overlaps the iris; lower lid meets it tangentially. The caruncle (inner corner) sits forward of the outer canthus in ¾.
Placement: eye line is not perfectly horizontal in perspective—wrap it like a belt around the head. Maintain the rule of fifths as a spacing guide, not a law.
Design knobs: distance between eyes (innocence vs intensity), upper‑lid crease height (alertness/femininity coding), sclera exposure (fatigue or fear).

6.2 Nose

Build as a wedge + keel: dorsum plane, side planes, and an under‑plane. The alar wings are separate volumes—avoid painting them as a gradient.
Placement: base of nose at lower third. In profile, nostril opening leans back (comma shape), not straight down.
Design knobs: bridge height (ethnic and character variance), tip bulb (softness/age), alar flare (energy/temperament cues).

6.3 Mouth & Dental Cylinder

Place the mouth on the cylinder projecting from the teeth. The corners track the cylinder’s tilt in ¾.
Upper lip’s central plane faces down (catches bounce); lower lip faces up (catches key). The tubercle makes a small down‑facing plane.
Placement: center of mouth usually halfway between base of nose and chin in neutral—but chin prominence changes this read.
Design knobs: mouth width (charisma/approachability), philtrum depth (age/masculinity coding), lower‑lip volume (youth vs gauntness).

6.4 Ears

A complex shell with a simple silhouette. Landmark the helix, antihelix (Y‑fork), tragus, antitragus, concha.
Placement: align top with brow and bottom with base of nose in neutral. From ¾, the ear axis tilts with jaw angle.
Design knobs: attached vs detached lobes, helix thickness, ear rotation (adds quirk without breaking rigging).

6.5 Jaw, Chin, and Neck

Jaw defines gender/strength coding. Think two hard planes meeting at the gonion; the body tapers forward.
Chin: a forward wedge; avoid a “button pasted on.” Integrate into the dental cylinder and lower lip shelf.
Neck: two columns—the sternocleidomastoid (SCM) from mastoid to clavicle, and the trapezius slope. Place Adam’s apple as a small forward keel on males.

7) Ethnic, Age, and Body‑Type Variation (Respectful Range)

Design within credible anatomical bounds while honoring diversity:

Ethnic variation: nasal bridge/width, alar flare, brow prominence, epicanthic folds, supraorbital shape, jaw angle. Treat as parameter sliders, not stereotypes.
Age: infants have bigger crania, smaller faces, low bridges, fuller fat pads; elderly lose fat pads, gain planar sharpness and skin folds.
Body‑type: low body fat reveals bone/plane edges; high body fat softens transitions and deepens nasolabial/beard planes.

Production note: Record your parameter ranges on a facial taxonomy sheet so modeling and rigging teams can build reusable targets.

8) Emotions: From Planes to Expressions

Expressions are controlled plane rotations caused by muscle groups. A practical, art‑first subset (loosely echoing FACS):

Joy (Duchenne): Zygomaticus major lifts mouth corners and orbicularis oculi squeezes lower lid → cheek plane rides up; crow’s‑feet bevels appear.
Anger: Corrugator pulls brows down/medially → deep V in glabella plane; levator labii may flare alar wings; masseter tension squares the jaw plane.
Sadness: Inner brows raise (frontalis medial) creating a tilted roof; mouth corners pull down (depressor anguli oris) forming oblique shadow planes.
Fear/Surprise: Brows elevate (frontalis), upper lid retracts exposing sclera; mouth opens and stretches the lip cylinder.
Disgust: Levator labii lifts upper lip and one alar wing → asymmetrical nose under‑plane becomes dominant.

Concepting tip: Key the three read levels—(1) silhouette of brows/jaw; (2) mid‑range plane shifts at eyes/cheeks; (3) micro wrinkling only if the camera will see it.

9) Lighting the Planes for Readability

Key from ¾ front to reveal forehead → zygoma → nasal dorsum → upper lip bevel → chin shelf.
Rim to separate the lateral head plane from the background.
Under‑light sparingly to read nasal under‑plane and philtrum when designing creature/heroic looks.
For stylized pipelines, exaggerate plane contrast; for real‑time realism, keep transitions soft and rely on roughness variation.

10) Hairlines, Brows, and Beards as Plane Devices

Treat keratin elements as shape groups controlling edge contrast:

Hairlines define the top plane break; recession patterns change forehead proportion.
Brows anchor the supraorbital bevel; vary thickness and taper to steer eye emphasis.
Beards obscure jaw plane—use to cheat jaw strength or age; keep breakup along the gonial angle for crisp reads.

11) Production Alignment: What Downstream Teams Need

Orthos & Turnarounds: front, ¾, profile, and back with clearly indicated plane breaks (thin vs thick line weight or color bands).
Expression Set: at least neutral + 5 primaries (joy, anger, sadness, fear/surprise, disgust). Include extreme phonemes (A, E, F/V, M, L) on the mouth cylinder.
Topology‑aware callouts: mark nasolabial fold flow, eyelid loops around the orbit, and mouth corner geometry (avoid single‑vertex pinches).
Blendshape Budget: define which expressions are pose‑based vs texture‑driven (wrinkle maps). Note asymmetry allowances.
LOD Strategy: specify which plane details are geometry vs normal/roughness. Preserve the zygoma and jaw in low LODs; wrinkles/pores move to textures.
Material IDs: skin, teeth, wet line (lip), sclera/iris, lash/brow, hair—call roughness/SSS notes per zone (oily T‑zone vs dry cheeks).

12) Common Failure Modes & Fixes

Sticker eyes/lips: fix by modeling eyelid shelves and the lip cylinder before painting.
Mushy cheeks: cut a bevel under the zygoma; separate fat pad from malar plane.
Floating nose: integrate nasal side planes into cheek with a visible alar‑to‑cheek transition.
Jaw drift in ¾: re‑establish center and jaw hinge; project a jaw angle line toward the ear.
Expression reads wrong at distance: reduce wrinkle noise, amplify plane rotations (brow tilt, mouth corner arcs).

13) Workflow: From Block‑In to Polish

Axis & belts: center line, brow belt, nose belt, mouth belt.
Macro planes: forehead, zygoma, nose prism, mouth cylinder, jaw wedge.
Feature volumes: lids as caps; alar wings as separate lobes; lips as three‑plane forms; ear shell.
Transition bevels: infraorbital, nasolabial, masseter.
Lighting test: quick grayscale under a single key to validate plane logic.
Expression pass: rotate planes, then add micro wrinkles last.
Production pass: orthos, neutral + expressions, topology/rigging notes, material IDs.

14) Drills & Studies (Daily/Weekly)

Daily (15–30 min): 5 quick 3D‑to‑2D plane studies (Asaro‑style) from photos; 2 expression flips (neutral → emotion) focusing on plane rotation.
Weekly: 1 multi‑angle head sheet (front/¾/profile) of a unique craniofacial type; 1 expression pack of 6 poses; 1 topology‑aware callout page.
Monthly: 3 character heads across different age/ethnic/body‑type ranges with consistent planar style guide; add orthos and blendshape notes.

15) Checklists

Block‑In: axes set • belts wrap in perspective • macro planes read in flat light.

Features: lids are volumes • nose has under‑plane • lips ride the cylinder • ear anchors to jaw and zygoma.

Expression: brows tilt/translate • cheeks compress/raise • corners arc on the cylinder • asymmetry present.

Production: orthos delivered • expression set defined • material IDs labeled • topology flow noted • LOD & wrinkle map strategy declared.

16) Closing

Mastering planar thinking gives you a shared language across concept and production. When your planes are clear, lighting tells the story, expressions land at a glance, and the model/rig teams can carry your intent all the way to launch. Treat the head as engineered sculpture—simple blocks first, precise bevels second, and character in the micro planes last.