Chapter 2: Proportion Passes & A / B / C Iteration (30% Deltas)

Created by Sarah Choi (prompt writer using ChatGPT)

Proportion Passes & A/B/C Iteration (30% Deltas) — From Brief to Package (Prop Concept Pipeline)

Proportions are the steering wheel of a prop’s identity. Before ornament, materials, or micro‑mechanics, proportion decides class, mood, and usability at a glance. A disciplined series of proportion passes—paired with an A/B/C iteration strategy that enforces ~30% deltas between options—lets you travel from ambiguous brief to confident handoff without getting lost in small tweaks. This article frames a repeatable approach for both concept and production artists, connecting Ideation → Iteration → Finals → Handoff with measurable checkpoints.

1) Why Proportion Passes Come First

Proportion is the most affordable variable to change early and the most expensive to change late. It governs far‑read silhouette, balance, and hand fit. When proportions are right, everything downstream—socket positions, rigging arcs, LOD budgets—gets easier. When they’re fuzzy, teams compensate with surface noise and FX, which hurts readability and schedule. A proportion pass is not decoration; it’s structural decision‑making that locks what the camera and the player will feel most.

2) The A/B/C Mindset and the 30% Rule

A/B/C iteration produces three deliberately different options rather than three near‑duplicates. The 30% delta rule forces each branch to shift at least a third of its visual gestalt—via scale ratios, mass distribution, or dominant axis—so that reviewers can make a strategic choice, not a taste pick. Thirty percent is large enough to be obvious at a glance yet small enough to remain within the brief’s footprint. This avoids the “mushy middle” where every option is safe and none is decisive.

3) From Brief to Proportion Hypotheses

Distill the brief into a one‑sentence intent and identify the governing proportions implied by function. A shoulder‑stocked scanner suggests a long primary axis with a rear counter‑mass; a ritual dagger suggests a 1:1.62 handle‑to‑blade goldenish ratio; a field medkit implies a shallow depth for quick access. Write 2–3 proportion hypotheses like headlines: “Forward‑biased cutter,” “Neutral‑balanced tool,” “Rear‑weighted precision device.” These become your A/B/C starting points.

4) Building A/B/C with Purposeful Levers

Choose proportion levers that move the read meaningfully: overall length, thickness, grip‑to‑barrel ratio, body‑to‑signal area, void‑to‑mass ratio, and stance (horizontal vs. vertical bias). For A, push stability and serviceability: thicker body, lower aspect ratio, larger flats for labels. For B, aim for neutrality and baseline ergonomics. For C, lean into spectacle or novelty: elongated axis, pronounced negative space, exaggerated counterweight. Keep line weight and rendering uniform to ensure the comparison is about proportion, not finish.

5) Measuring “30%” in Practice

Treat 30% as a measurable change across at least two levers. If B has a 100mm grip length and a 160mm barrel housing, A might shrink grip to 70mm and expand housing to 200mm (−30% / +25%), while C could extend grip to 130mm and compress housing to 120mm (+30% / −25%). For non‑linear reads like negative space, measure the percentage of bounding box occupied by voids vs. solids. Record ratios (e.g., 2.4:1 body‑to‑signal) in a corner note so production can track what must not drift.

6) Proportion Pass Workflow (Ideation)

Start with thirty to sixty quick silhouettes clustered around your three hypotheses. Keep them monochrome and normalize their overall bounding boxes for fair comparison. Pin or tile them in three columns (A/B/C) and tune within each column until the family reads are stable. Avoid detailing; only adjust mass placement, axis bias, and voids. When a silhouette starts to rely on detail to be interesting, it’s a sign the proportions aren’t carrying the idea.

7) Cross‑Band Read Checks

Proportion passes must survive far, mid, and close reads. At far distance, confirm that each option’s primary vector is unmistakable. At mid distance, check that functional zones (grip, power, head, latch) have enough area to host clear interfaces. Up close, ensure there’s room for believable thicknesses—gaskets, screws, panel lips—without collapsing clearances. If a proportion set fails any band, fix proportions before adding features; details cannot save a broken massing.

8) Ergonomics and Balance as Proportion Tests

Mock hand fit with a simple rectangle for palm width and cylinders for finger reach. Plot center of mass relative to grip and typical use angles. For hanging props (holsters, straps), test gravity lines and snag risks. For two‑handed props, ensure that the secondary grip line neither occludes the primary silhouette nor forces unrealistic shoulder widths. Production can turn these tests into a quick 3D blockout to validate that the A/B/C options are physically plausible before anyone invests in polish.

9) Iteration Within Branches: 10–15% Micro‑Shifts

Once the A/B/C trunks are chosen, iterate within each branch using smaller 10–15% proportion tweaks to refine use cases. On the “Forward‑biased cutter,” you might enlarge the head by 10% and slim the handle by 12% to improve recoil read. These micro‑shifts are for optimization, not identity changes. Keep a changelog so you can revert if a tweak erodes the branch’s promise.

10) Locking Ratios Before Detail

Before adding surfaces or ornament, lock three to five ratios that encode the prop’s character: overall aspect ratio; body‑to‑signal area; grip length to circumference; void‑to‑mass percentage; and socket spacing in module units. Present these ratios alongside line drawings so the art director approves both look and math. Name them in the file and keep them visible on every sheet; downstream teams will treat them like “never break” rules.

11) Value Mapping to Support Proportion

Freeze a grayscale value plan that amplifies the massing: body value vs. frame value vs. signal value. Value should respect proportion zones—broad, low‑frequency areas get flatter values; interface zones receive sharper contrasts. If value is fighting proportion (for example, a dark handle that visually shortens the grip), adjust proportion or value, not just texture. Value lock is your guardrail against later color temptations that could undermine the read.

12) Transition to Finals: From Ratios to Reality

With ratios locked, add functional anatomy only where proportions allow: seams on planes, latches on flats, gaskets at pressure boundaries. Maintain the A/B/C character while making real surfaces. Introduce a single spectacle lever per branch—an emissive seam, a translucent reservoir, an anisotropic ring—that scales with LOD. Confirm that each lever sits on a proportion zone designed to carry it; never ask a 5mm fillet to host your legendary read.

13) Review Strategy: Comparative, Not Absolute

Present A/B/C side‑by‑side with their ratio cards and value maps. Ask reviewers to pick a strategy (“we want the forward‑biased silhouette for readability in combat”) before they pick an option. Capture the decision rationale on the sheet. If debate centers on taste, return to proportion logic and distance‑band goals to recalibrate. The point of 30% deltas is to make disagreement productive by making differences explicit.

14) Handoff for Production: What Must Not Drift

Package the chosen option(s) with a proportion spec: dimensioned orthos, key ratios, socket map with coordinates, center‑of‑mass estimate, and recommended materials by zone. Include a quick blockout OBJ/FBX or parametric guide with empties at pivots and sockets. Call out tolerances (e.g., “grip circumference 95–105mm”) and explicitly list which ratios are flexible vs. fixed. Provide an LOD note describing which proportion cues must survive at each distance band.

15) When to Break Your Own 30% Rule

You can violate the 30% delta when the brief is highly constrained (licensed items, historical replicas) or when the pipeline has already invested heavily in animations that lock proportions. In those cases, create internal 5–10% micro‑sets aimed at specific goals—comfort, manufacturability, or readability in a new lighting scenario—and document why deviations are limited. Communicate clearly that this is optimization, not exploration.

16) Common Failure Modes and Fixes

If all three options feel the same, your deltas are too small or all changes happen along the same lever. Introduce orthogonal levers: flip axis bias, reassign negative space, or invert body‑to‑signal ratios. If a branch looks exciting but breaks in blockout, preserve its proportion idea by redistributing mass, not by adding surface décor. If reviews always pick the “safest” option, raise the stakes: make the bold branch even clearer so decision makers can defend it with confidence.

17) Metrics That Make Proportion Real

Track quick tests for each branch: a 5‑second recall sketch test for identity, a distance legibility check at gameplay scales, a hand‑fit checklist for grip length and clearance, and a socket spacing sanity pass. Record pass/fail with notes and tie them to ratios. Over time your team will build a private library of proportion benchmarks per genre—what makes a “hero” medkit vs. a “common” one in your world.

18) Carrying Proportion Through Texturing and FX

In production, proportion is easy to erode through textures, decals, and FX blooms. Guard it by mirroring the ratio zones in your texture masks and material instances. Keep emissive intensity clamped so signal areas do not visually expand beyond their intended percentage of the silhouette. Treat grime and wear as frames that reinforce mass, not random noise that flattens it. In cinematics, align camera blocking with the prop’s dominant axis to preserve the proportions you fought to establish.

19) A Repeatable Routine

  1. Distill the brief and write three proportion hypotheses. 2) Generate A/B/C silhouettes with ≥30% deltas across at least two levers. 3) Normalize, compare, and select trunks. 4) Run hand‑fit and blockout sanity checks. 5) Lock core ratios and value map. 6) Iterate 10–15% within branches to refine. 7) Add functional anatomy that respects massing. 8) Choose a single spectacle lever per branch. 9) Review comparatively and capture rationale. 10) Package a proportion spec for production: orthos, ratios, sockets, pivots, tolerances, CoM. 11) Protect proportions through texturing, FX, and LOD with masks and clamps. 12) Archive the deltas for future variants.

20) Closing Thought

Great props feel inevitable because their proportions make sense before any detail arrives. A/B/C with 30% deltas gives teams the courage to choose—and to understand why they chose. When each proportion decision is visible, measurable, and guarded from ideation through handoff, your pipeline produces assets that read instantly, animate cleanly, and scale into families without losing their core identity.