Chapter 1: Bony Landmarks & Functional Anatomy

Created by Sarah Choi (prompt writer for ChatGPT)

Bony Landmarks & Functional Anatomy (Mobility Ranges)

Characters become believable when their surfaces obey the skeleton beneath. For character concept artists on both the concepting side and the production side, knowing bony landmarks and functional anatomy protects readability, prevents animation pain, and makes costumes/gear behave. This article focuses on skeletal anchors, muscular overlays, and real‑world mobility ranges you can design around, with practical deliverables for indie and AAA pipelines.

1) Why Landmarks Matter to Concept Art

  • Readability: Landmarks shape silhouette kinks and planes that guide the eye (acromion, ASIS, patella).
  • Construction: They’re measuring posts for proportion rails (clavicle span, rib cage height, pelvis width).
  • Rigging & Cloth: Placing seams, plates, and straps away from hotspots (olecranon, lateral epicondyle) avoids clipping.
  • Gameplay: Start/impact silhouettes depend on joint ranges; impossible poses break tells and counterplay.

2) The Skeletal Map — Primary Landmarks (Front/Side/Back)

Skull & Neck

  • Zygomatic arch (cheek ridge) → sets face width; crucial for helmet fit and cheek plane breaks.
  • Mastoid process (behind ear) → anchor for sternocleidomastoid; informs neck strap routing.
  • Mandible angle → defines jaw silhouette; shave/extend to alter age/power reads.

Shoulder Girdle

  • Clavicle (S‑curve) → rotates as a unit with scapula; visible notch at sternum. Avoid hard collars that cage clavicle elevation.
  • Acromion (tip of shoulder) → upper silhouette point; pauldron pivot lives here.
  • Scapular spine & inferior angle → surface ridge on back for cape/strap placement; glides with arm elevation.

Torso

  • Sternal notch (suprasternal) → helmet/hood clearance; good anchor for pendants.
  • Rib cage edge (10th costal arch) → underboob/armor lower edge; don’t force belts too high.
  • ASIS (front pelvis spikes) → visible hip points; belt anchor; protects from rig twist.
  • PSIS (back dimples) → strap crosspoint; cape yoke landing.

Upper Limb

  • Humeral greater tubercle (under acromion) → defines shoulder ball mass.
  • Medial/Lateral epicondyles (elbow ridges) → don’t run rigid bracers over them without articulation gaps.
  • Olecranon (elbow tip) → hinge apex; brace clearance needed.
  • Ulnar styloid & radial styloid (wrist bumps) → glove cuff scallops; watch for watch‑strap occlusion.

Hand

  • Metacarpal heads → knuckle silhouette; plate/brace must allow flexion.
  • Thenar/hypothenar pads → glove patterning; emitter sockets avoid high‑compression pads.

Pelvis & Lower Limb

  • Greater trochanter (lateral hip bump) → pocket/holster height; stance width.
  • Patella (kneecap) → knee armor pivot; sits within tendon, glides superior with extension.
  • Tibial tuberosity & crest → shin ridge; greave centerline.
  • Lateral/medial malleoli (ankle bumps) → boot cuff asymmetry; avoid circular cuffs that clip.

Foot

  • Calcaneus (heel) & navicular (medial instep) → boot last shape; spur/heel guard placements.

3) Muscular Overlays — What Actually Shows

  • Deltoid: Three heads wrap from clavicle/scapula to humerus; creates cap over greater tubercle. Read changes drastically through arm elevation.
  • Pectoralis major: Inserts at humerus; groove forms the delto‑pec line—a key rhythm for chest armor seams.
  • Trapezius: From skull to scapula and spine; defines neck–shoulder slope; cape rests here.
  • Latissimus dorsi: Back sweep to humerus; governs side silhouette and backpack strap clearance.
  • Rectus abdominis & obliques: Define armor plate spacing; twisting compresses one side, stretches the other.
  • Gluteus medius/maximus: Hip silhouette and seat of belts; leg raise compresses glute fold.
  • Quadriceps group: Rectus femoris crosses the hip; kneeling stretches it—avoid tight front‑thigh plates.
  • Hamstrings: Form the posterior thigh tension in crouch; long skirts must slit here.
  • Gastrocnemius/soleus: Calf bellies shape boot tops; ankle plantarflexion bulks posteriorly.

Design note: Show muscle direction with panel lines/stitching to sell function under cloth.

4) Functional Mobility Ranges (Design‑Ready Numbers)

Ranges vary by body and training; use these approximate safe design rails unless your IP needs exceptions.

Shoulder (GH joint + scapula)

  • Flexion (forward raise): ~160–180°.
  • Abduction (side raise): ~150–170° (first ~30° at GH, rest from scapular rotation).
  • External rotation (arm at side): ~60–90°; internal: ~60–90°.
  • Design: Pauldrons need clearance arcs; collars must allow clavicle elevation.

Elbow

  • Flexion: ~140–150°. Extension: 0° (–5° hyperextension possible).
  • Pronation/Supination (forearm rotation): ~80–90° each.
  • Design: Bracers should split at cubital crease; forearm weapon mounts must respect radius/ulna roll.

Wrist

  • Flexion/Extension: ~80°/70°. Ulnar/Radial deviation: ~30°/20°.
  • Design: Gauntlet cuffs need flares and asymmetric cuts around styloids.

Spine

  • Cervical flex/extend: ~45–60°/~45–60°. Rotation: ~60–80°.
  • Thoracic rotation: ~30–45°. Lumbar flexion: ~40–60°; extension ~20–35°.
  • Design: Backpack plates allow thoracic rotation; avoid rigid corsets across lumbar.

Hip

  • Flexion: ~120°. Extension: ~20°. Abduction: ~40–45°. External rotation: ~45°.
  • Design: Belt/loin armor must clear ASIS and inguinal line; holsters follow GT (greater trochanter) arc.

Knee

  • Flexion: ~130–150°. Rotation (flexed): ~10–15°.
  • Design: Knee plates hinge around patella; greaves split over tibial crest.

Ankle

  • Dorsiflexion/Plantarflexion: ~20°/~45–55°. Inversion/Eversion: ~30°/~20°.
  • Design: Boot cuffs step over malleoli; spats must allow dorsiflexion for stairs.

5) Landmark‑Driven Design: Seams, Armor, and Gear

  • Seam placement: Route seams along low‑stretch lines (delto‑pec groove, oblique fascia) to prevent texture distortion.
  • Armor breaks: Float plates over bony areas; leave soft gaps over joint lines (olecranon, patella) for deformation.
  • Strap logic: Cross scapular spine, not the acromion; anchor belts to ASIS/PSIS; holsters ride the greater trochanter.
  • Holster/reload paths: Map arcs around landmarks (ulnar side for mag pulls; radial side for blade draw) to avoid wrist pinch.

6) Camera Contexts & Landmark Emphasis

  • FPP: Emphasize wrist styloids, knuckle planes, and extensor tendon paths; keep cuffs cut away on radial side for reload clarity.
  • TPP: Deltoid cap, clavicle S‑curve, ASIS bumps, and knee plate pivots anchor the silhouette at 10–20 m.
  • Isometric: Exaggerate acromion and patella reads; simplify rib/ab blocks into bold shapes.
  • Cinematics: Add secondary planes to zygomatic, mandible, and scapular spine; micro‑wrinkles should follow muscle direction.

7) Indie vs AAA: Who Owns Anatomy Decisions

Indie. The concept generalist bakes landmark literacy into silhouettes, pose sheets, and callouts. You’ll do paintovers on block‑ins to fix seam/armor intersections and adjust gear to safe arcs.

AAA. Exploration sets anatomical stylization rules; production concept encodes landmarks in orthos and callouts; tech art and animation enforce ranges and flag exceptions. Vendor guides include landmark overlay plates and “no‑twist/no‑pinch” zones.

8) Deliverables That Encode Anatomy

  • Landmark Overlay Plate: Front/side/back with labeled bony points and seam/strap suggestions.
  • Mobility Range Pose Sheet: Start/hold/impact silhouettes with angular annotations (e.g., shoulder abduction 120°).
  • Armor/Cloth Break Map: Color‑coded zones: rigid, semi‑rigid, flex; with bevel and clearance specs.
  • Hand Function Sheet: Grips (power, precision, pinch) with knuckle alignment and wrist deviation notes.
  • Foot/Boot Last Diagram: Heel, arch, toe‑spring for gait; stair test sketch.

Package with naming/versioning and a short change log.

9) Failure Modes (and Quick Fixes)

  • Collar bites clavicle: Drop front plate; add notch at sternal end; bevel under acromion.
  • Pauldron blocks abduction: Pivot at acromion with floating cap; add deltoid cutout; shorten cape yoke.
  • Bracer pins elbow: Split across cubital crease; soften over olecranon; add elastic seam.
  • Thigh plate grinds in sit: Chamfer at ASIS; add crotch gusset; split plate over rectus femoris.
  • Boot locks ankle: Lower medial side for dorsiflexion; notch around malleoli; add tongue gusset.

10) Drills (Daily/Weekly)

Daily (20–30 min): Landmark tracing on photos (front/side/back); redraw from memory; add seam/strap routes.

Weekly (60–90 min): Mobility sheet for one joint (shoulder or hip) with start/impact silhouettes; armor/cloth break map for a kit piece.

11) Review Gates & Collaboration Map

Gate A — Landmarks Locked: Overlay plate approved; proportion rail aligned; seam/strap policy drafted.

Gate B — Mobility Validated: Pose sheet ranges reviewed by animation/tech anim; problem arcs flagged.

Gate C — Build Package: Orthos with joint centers, armor/cloth break map, hand/foot function sheets; vendor acceptance checklist attached.

Collaborators: Design (tells, kit ergonomics), Animation/Tech Anim (ranges), Character/Tech Art (topology, shaders), VFX/Audio (emitter points on bony flats), UI/UX (icon silhouettes), Cinematics (close‑up planes), Production/Outsourcing/QA (acceptance).

12) Final Thought

Anatomy for concept artists isn’t memorizing every muscle—it’s seeing the hinges. If you can place the bones, respect the ranges, and route seams/gear where bodies truly move, your designs will read, animate, and ship with far fewer surprises. Start with landmarks, layer functional anatomy, and package those insights so every teammate builds on the same human truth.