Sarah Clarity Studios

Chapter 1: Metrics

Created by Sarah Choi (prompt writer using ChatGPT)

Metrics for Mecha: Reach, Step, Clearance, Hit Boxes

In mecha development, “metrics” are the invisible rules that make your design playable, animatable, and shippable. They are not just numbers; they are agreements between disciplines about how big the mech is, how far it can move, what space it occupies, and how players and enemies interact with it. When concept artists understand metrics, their designs stop fighting the game and start supporting it. The result is faster iteration, fewer late redesigns, and mechs that feel powerful because their motion and behavior are consistent with their visuals.

This article is written equally for concept artists on the concepting side and for concept artists on the production side. If you are early in ideation, metrics help you choose silhouettes and proportions that will survive gameplay constraints. If you are later in production, metrics help you create packages and callouts that downstream teams can implement without guessing.

What “metrics” mean in a mecha game

Metrics are the measurable pieces of a mech that affect gameplay and implementation. Reach is how far an arm, weapon, or tool can effectively interact. Step is how far a single stride moves the mech and how quickly it can reposition. Clearance is the safety space needed to avoid collisions—between the mech and the environment, and between mech parts and each other. Hit boxes are the gameplay volumes used for damage, melee contact, targeting, and physics interactions.

These metrics are tied to motion and behavior. A heavy siege mech that looks like a walking fortress should have slower acceleration and larger turn radius, but its hit boxes and clearance should communicate that weight without making it constantly snag on level geometry. A nimble scout mech should have smaller collision volumes and more forgiving step and clearance behavior so it can navigate spaces quickly.

Why concept artists should care (even if you don’t touch engine tools)

Metrics shape what is possible. If your shoulder silhouette is extremely wide, it may force wider doorways and more generous cover spacing, or it may create constant collision issues. If your legs are very short relative to the torso, your step metric may look weak unless the animation compensates with faster cadence, which can feel comical for a “heavy” mech. If your weapon is mounted far from the centerline, recoil and physics might demand stabilizers or a bracing behavior.

For concepting-side artists, metrics help you make better early choices: which silhouettes will actually fit the game spaces, which weapons are readable at gameplay camera, and what motion behaviors the mech can plausibly support. For production-side artists, metrics help you communicate intent: where hit boxes should live, what clearance assumptions were used, and what behaviors need visual support (thruster bursts, stomp shockwaves, charge tells).

The shared language: bounding volumes and “truth shapes”

Every mech has at least two shapes: the rendered model and the “truth shape” the game uses for collision and targeting. The truth shape is often simpler than the visual mesh because it must be stable, performant, and predictable. These truth shapes include collision capsules, boxes, and convex hulls for the body; separate hurt volumes for weak points; and sometimes additional volumes for melee, stomp, or AOE attacks.

Concept artists can help by thinking in “bounding silhouettes.” When you design an extreme silhouette feature—huge fins, antenna arrays, spiky armor—ask what the truth shape should be. Will those features be non-colliding cosmetic appendages? Will they be included in the hit box? Will they be destructible? If you don’t specify, the game will decide later, and the decision may undermine your design intent.

Reach: not just arm length, but interaction design

Reach includes arm length, shoulder pivot placement, elbow clearance, and hand/tool size, but it also includes what the game counts as an interaction. A melee strike may use an animation-driven hit volume that extends beyond the hand, while a grab may require precise contact.

From a design partnership perspective, reach is a gameplay promise. If a mech has long forearms and a spear-like weapon, players will expect it to control space at distance. If the actual reach metric is short, the design will feel misleading. Conversely, if a mech looks compact but has huge reach due to invisible hit volumes, it can feel unfair to enemies or confusing to players.

Concepting-side artists can support reach by designing clear “reach landmarks” that match the intended gameplay. Long-limbed mechs should have believable joint structures and counterbalance. Close-range brawlers can emphasize compact, forward-weighted arms that read as powerful at short distance.

Production-side concept artists can add reach callouts that show maximum extension poses and note which parts are expected to drive hit volumes: “forearm + blade edge,” “fist contact,” “shoulder spike sweep,” or “grapple hook tether.” These notes help animation and gameplay designers align visuals and mechanics.

Step: stride length, cadence, and traversal behavior

Step metrics are about how far the mech travels per stride, but the player experiences them as speed, weight, responsiveness, and control. A long stride can make a mech feel efficient and powerful, but it can also break navigation if the mech constantly oversteps small cover or cannot stop precisely.

Step also interacts with animation style. A heavy mech can move quickly if it has high cadence and short steps (think “stompy run”), but that might contradict the fantasy of mass unless secondary motion and audio sell the weight. A lighter mech can have longer steps and lower cadence with springier motion, but this must match the scale.

Concepting-side artists can design legs and feet that support the intended step behavior. Long legs and narrow feet suggest speed but can look unstable unless you add gyros, tail counterweights, or stabilizers. Short legs with broad feet suggest stability but may limit step length unless boosted movement is part of the behavior.

Production-side concept artists can help by including a small “gait sheet” style callout: a few key poses that show foot plant, toe-off, and knee lift, plus notes on expected cadence (fast, medium, slow) and whether the mech uses assist mechanisms like thrusters, heel wheels, or magnetic adhesion.

Clearance: environment fit, self-collision, and readability

Clearance is the space a mech needs to move without colliding with itself or the environment. In gameplay terms, clearance determines whether a mech fits through doors, around corners, between props, and behind cover. It also determines whether animation can hit dramatic poses without armor intersections.

Clearance is a frequent source of late-stage pain because it is easy to ignore in 2D and expensive to fix in 3D. If a mech has wide shoulders, long back-mounted cannons, or huge wing-like fins, the environment team needs to know whether those parts collide, fold, or “ghost” through geometry. If the parts fold, the animation and rigging teams need a mechanism. If they ghost, the VFX and audio teams may need cues so the player understands what is happening.

For concepting-side artists, the best habit is to do “clearance honesty checks” early: imagine the mech in the game’s most common spaces and camera angles. If you don’t know those spaces yet, assume typical constraints: doorways, corridors, cover pieces, and traversal gaps.

For production-side concept artists, clearance can be communicated with simple diagrams: a top-down footprint, a side profile height envelope, and notes such as “backpack folds in combat,” “shoulder pylons are cosmetic and non-colliding,” or “winglets retract during sprint.” Those statements allow design, physics, and level teams to implement consistent rules.

Hit boxes: fairness, readability, and weak-point design

Hit boxes are often misunderstood as purely technical, but they are a core part of player fairness and game readability. Players learn quickly what counts as “the body” and what counts as “decoration.” If the hit boxes don’t match the visual, the game feels inconsistent.

In mecha games, hit boxes are often layered. There may be a broad body hurt volume, smaller weak-point volumes (cockpit, sensor head, power core), and special-case volumes for shields or armor plates. There may also be separate volumes used for melee contact, stomp shockwaves, or projectile deflection.

Concept artists can support hit box clarity by designing weak points that are visually legible and logically protected. A sensor head can be small but exposed; a power core can be buried but telegraphed with vents or glow seams; a cockpit can be armored but visible through canopy language. If the design hides all weaknesses, gameplay may compensate with arbitrary weak points, which can undermine the fantasy.

Production-side concept artists can include “hit box intention” notes without dictating exact implementation. For example, you can indicate that shoulder pods are armor but not critical, while the torso core is critical, and the head is a sensor weak point. This helps gameplay designers place hurt volumes in ways that respect the design.

How metrics connect to animation and rigging

Animation expresses metrics through pose and timing. A mech with long reach must show extension and follow-through; a mech with short reach must show commitment and body movement to get close. Step metrics show up in foot timing and weight shifts. Clearance constraints show up in how often a mech tucks its limbs, rotates its torso, or adjusts its backpack.

Rigging makes metrics possible by providing stable pivots, deformation solutions for joints, and constraints for pistons, cables, and sliding armor. If your design uses “impossible” joints, the rig will either become expensive or the animation will avoid using the full motion, making the mech feel restricted.

For concepting-side artists, the most useful practice is to design motion mechanisms as part of the silhouette. Telescoping pistons, sliding armor overlaps, and retracting fins are not just details—they are the story of how the mech obeys its metrics.

For production-side concept artists, it helps to provide at least one “extreme pose” sheet: high knee lift, deep crouch, overhead reach, full twist. These are not final animations; they are constraint tests. When you include them, riggers and animators can spot issues early.

How metrics connect to physics and AI

Physics cares about mass distribution, contact points, and stability. A mech that looks top-heavy may need a wider stance or active stabilization behaviors to feel believable. Foot size and shape affect ground contact and how the mech interacts with slopes, rubble, and destructible props. Recoil, knockback, and ragdoll-like reactions depend on how the mech’s body volumes are defined.

AI cares about navigation, line of sight, and target evaluation. Hit boxes influence how AI aims and what it considers a “good shot.” Clearance affects pathfinding—if the mech’s footprint is large, it may need wider routes or different behavior in tight spaces. Reach and step influence attack selection: an AI with long reach should favor mid-range pokes and zone control; an AI with short reach should favor lunges, charges, or grapples.

Concept artists can support physics and AI by designing readable stances and stable silhouettes. If a mech is meant to be hard to topple, show low center-of-mass cues (wide hips, heavy feet, stabilizer fins). If a mech is meant to dodge, show lightweight cues (narrow torso, thruster jets, articulated ankles).

How metrics connect to VFX and audio

VFX and audio turn metrics into feeling. A big step metric should read as ground impact: dust, debris, screen shake (where appropriate), and low-frequency audio. A long reach attack needs anticipation and contact feedback: trails, sparks, impact flashes, and a sound envelope that matches the swing.

Clearance and collision rules also need communication. If a backpack retracts to fit through doors, that needs a visual and audio cue so it doesn’t feel like clipping. If wings are cosmetic and do not collide, you may still want subtle VFX or motion to communicate that they are lightweight appendages.

Hit box clarity benefits from VFX too. Weak points can have distinct glow, smoke, or electrical flicker when damaged. Shields can have impact ripples that define the defensive volume. Audio can distinguish hits on armor versus hits on critical systems.

Concept artists can contribute by indicating where VFX “hooks” live: vents, thruster nozzles, heat seams, impact plates, and sensor arrays. These cues help the player understand metrics intuitively.

What to include in a metrics-minded concept package

A metrics-minded concept package does not need to be technical documentation, but it should include a few key pages that communicate space and behavior. A front/side/top footprint envelope tells the level team how the mech occupies space. A maximum reach pose tells animation and gameplay what the design expects. A few clearance callouts tell rigging and physics what parts retract, slide, or remain non-colliding. A weak-point diagram tells design and VFX where to place damage feedback.

On the concepting side, you can keep this light: one extra page of simple diagrams and a few sentences of intent. On the production side, you can make it more explicit: consistent proxy shapes, pivot markers, and clear notes about what is cosmetic versus gameplay-relevant.

A practical mindset: make metrics visible, not hidden

The strongest mecha designs make their gameplay truths visible. A long-reach mech looks long-reach. A heavy step sounds heavy and kicks up debris. A fragile weak point is readable and protected in a way that creates interesting play. When you design with metrics in mind, you are partnering with design, animation, rigging, physics, AI, VFX, and audio all at once, because you are designing the rules of the mech’s body.

If you remember one principle, make it this: every metric is a promise. Your concept should either visibly support that promise or clearly note where the game will simplify it. When you do that, your mechs feel consistent, fair, and powerful—because the whole team is building the same creature from the same measurements.