Chapter 1: Metrics

Created by Sarah Choi (prompt writer using ChatGPT)

Character Metrics: Reach, Grip, Cloak Lengths & Collision Zones

Partnering with Design, Animation, Tech Art, Narrative, UI & Audio (Metrics • Motion • Story • Interaction)

Metrics are the shared language that lets a studio ship characters that look right, move right, and play right. They translate an idea’s silhouette grammar into numbers that design can balance, animation can stage, tech art can bind and simulate, narrative can justify, UI can frame, and audio can sell. This article lays out the practical metrics—reach, grip, cloak lengths, collision zones, and their neighbors—and shows how concept and production teams use them together from ideation through iteration to finals and handoff.

Begin by declaring a measurement system in engine units and a human baseline. If a project uses centimeters, fix a default human height (for example, 180 cm to eye at 168 cm) and document head count for artistic shorthand. All subsequent ratios—arm span, hand span, cloak hem clearance—should be recorded relative to this baseline and stamped on every page that could be extracted from the package. Consistency across cameras matters: note the gameplay focal length and eye height so that screenshots and paintovers do not lie about proportions or reach. When non‑human anatomies appear, define analogues (wingspan for arm span, tail base height for hem clearance) so the same logic stays portable across species.

Reach is gameplay in disguise. Designers think in radii: melee cones, interaction bubbles, pickup zones. Concept artists can shape those radii with arm length, shoulder span, and weapon geometry, but the numbers must be explicit. A readable striker might live at an arm span of 1.05–1.15× body height with a preferred attack arc of 110–140°, while a tank might compress to 0.95× with broader torso rotation and shield coverage. Annotate forward reach (shoulder pivot to palm center along the lunge path), lateral reach (shoulder to grip at T‑pose), and vertical reach (floor to finger tips overhead) so level design can place ledges and interactables that neither soft‑lock nor trivialize movement. Animation uses the same metrics to time anticipations and ensure that the hand arrives where the design expects without elbow hyperextension or shoulder pop.

Grip is the contract between anatomy and systems. A weapon grip diameter of 30–40 mm reads differently than 50–60 mm at gameplay distance and affects wrist safety and reload staging. Specify grip span (thumb tip to index tip across the handle), neutral wrist angle relative to the forearm during aim and interact, and allowable deviation before the pose looks broken. For two‑handed props, define the default inter‑hand distance and the travel needed for reloads or transforms. Tech art maps these to constraint targets and IK handles; audio then uses them to sync foley (cloth pull, leather creak, metal bite) to meaningful hand transitions. When you must push beyond human comfort for style, write the cheat plainly (e.g., “index metacarpal elongated +8% for silhouette; rig to preserve 15° ulnar deviation limit during aim”).

Cloak lengths and drape clearances are the difference between poetic and playable. Hem length relative to ground dictates snag risk and compositional chatter. A safe neutral target for dynamic cloaks is hem at 5–8 cm above ground in neutral stance, widening to 10–12 cm during walk to avoid step collisions and camera smear. For capes that must kiss the floor for drama in cinematics, declare a gameplay curl‑up or pin state that lifts hem during locomotion. Shoulder yoke width, back panel split, and weight distribution along the hem should be specified to control flutter versus billow; animation and tech art can then choose a sim preset (stiff, medium, flowing) that respects the intended mood. Narrative can justify weights, cuts, and rituals (e.g., battle‑frayed hems) without eroding simulation stability.

Collision zones are where art meets physics. Tech art will approximate bodies with capsules and boxes; concept can anticipate them by drawing proxy volumes directly on turnarounds and pose sheets. Define primary capsules (head, chest, pelvis, upper/lower limb pairs) with radii and extents, and mark secondary zones for backpacks, shields, tails, wings, and long hair. State minimum separations: shield‑hip daylight, backpack‑cape gap, pauldron‑neck clearance at 90° abduction. These gaps maintain read and reduce solver panic. For complex characters, include cross‑sections at elbows, knees, and ankle cuff areas that show how cloth routes around hardware and where collision should be forgiving versus strict. Animation will use the same zones to stage silhouettes that stay open under motion, and UI will avoid placing health bars or quest markers where collision creates noisy overlaps.

Metrics extend into camera and UI. A third‑person shoulder camera favors a clean shoulder skyline and a backpack depth that avoids over‑occlusion; write a maximum back projection (for example, ≤18 cm beyond scapula plane) and a minimum negative space under the armpit (for example, a triangular daylight of ~120 cm² at idle) so silhouettes breathe around reticles and damage numbers. For isometric or tactical views, cloak area and head‑to‑torso ratio dominate readability; set a head proportion floor (e.g., ≥1.2× studio human baseline) and a maximum cape planform area (e.g., ≤0.35× body rectangle) to prevent map clutter. UI can then design reticles, outlines, and damage pop‑ups that hug these shapes without erasing identity. Audio will exploit the same metrics to modulate footstep attenuation by cloak length and material, or shield size by impact timbre.

Narrative depends on measure as much as metaphor. A character who carries a ritual banner or heirloom blade must have defined spans that explain posture and motion. Declare banner height above head at neutral, trailing length behind heel at sprint, and safe lateral swing so crowds do not devolve into cloth chaos. Mark where heirloom wear lives—hem corners, sleeve elbows, scabbard mouth—in engine units so surfacing and audio can coordinate micro‑details (fabric fray hiss, buckle rattle) with animation beats. Story then reads through physics rather than text: a cloak that sits heavy because lore says it is weighted with river stones will also move heavy in simulation because you assigned it a stiff preset and shorter hem.

From ideation into iteration, keep metrics fluid but visible. Early silhouette banks should include a slim metric header—height, arm span, hand span, tentative hem clearance—so reviewers can judge feasibility while they judge appeal. As A/B/C proportion sets solidify, convert deltas into numbers (shoulder span +30%, forearm +15%, hand span +10%) and retest against interaction radii and collision zones. Mannequin pose sheets should use those metrics as gates: if the cast or guard pose violates wrist or shoulder limits, adjust massing and tool geometry before style choices calcify. Lighting renders should also carry scale bars; values that look dramatic but hide clearance breaches are lying to production.

Finals lock numbers as contracts. The orthographic sheet should list total height, shoulder and hip spans, pelvis height, leg length, head height, hand span, and foot length—alongside weapon lengths, grip diameters, and inter‑hand spacing for two‑handers. Cloak and skirt pages should call out hem clearance at neutral and locomotion, split depths, and pleat counts if they affect simulation tuning. The collision overview should depict capsule radii and offsets for body and gear, plus intended simulation zones and pin lines. A one‑paragraph “do not break” note preserves negative spaces: armpit daylight, shield‑hip gap, cape‑ground clearance. Export these with camera stamps and engine units so modeling, rigging, and tech art inherit truth, not vibe.

Handoff packages metrics for every department. Design receives interaction radii and ladder/ledge spacing; animation gets joint ranges, grip spans, and verified verb poses; tech art gets capsule sizes, sim regions, and socket coordinates relative to the pelvis or spine; UI gets safe framings and silhouette anchors; audio gets material IDs tied to footfall and cloth presets; narrative gets a lore capsule that maps symbols to wear and motion choices. When numbers disagree across pages, fix the pages; when numbers threaten beauty, change the design. Metrics are not the death of style; they are the scaffold that lets style survive engine reality.

Typical failure modes are preventable. The most common is decorative metrics—numbers posted after the fact to legitimize a drawing. The cure is to measure at the blockout and sculpt‑base stage, not at paintover. Another is camera drift: focal changes that make reach look longer or backpacks look shallower than they are. The cure is a locked camera rig and stamped exports. A third is cloth romance: hems that drag because the concept looks elegant, only to explode in simulation. The cure is hem clearance rules that you break only with a declared gameplay lift. Finally, the silent killer is noisy collision: too many small capsules and zero daylight. The cure is to simplify to primary volumes and preserve big negative spaces that read in camera and behave in physics.

For concept and production alike, metrics turn preference into evidence. They compress approvals, prevent avoidable rework, and align teams on what must be seen, felt, and heard. When reach, grip, cloak lengths, and collision zones are measured, annotated, and respected from brief to package, the character that thrills in a sketch remains thrilling in a crowd, in motion, and in the player’s hands.