Chapter 3: Shock, Rebound & Toe / Heel Behaviors

Created by Sarah Choi (prompt writer using ChatGPT)

Feet, Tracks & Ground Interfaces — Shock, Rebound & Toe/Heel Behaviors

If a mech feels weightless, it’s usually not the silhouette—it’s the landing. Shock, rebound, and toe/heel behaviors are the small motion truths that convince the audience that tons of mass are meeting terrain. A great ground interface design does two jobs at once: it creates traction and stability as a physical system, and it gives animation and VFX a believable “contact script” to follow. Even if you never show a spring, the viewer will look for a reason the mech doesn’t shatter its own joints every step.

For concept artists on the concepting side, this chapter gives you a vocabulary for designing feet and ground interfaces that imply compression, energy management, and controlled contact—so your drawings feel grounded. For concept artists on the production side, it frames shock and rebound as predictable beats that can be rigged, animated, and supported with effects without exploding scope. The focus here is toe/heel behavior across terrains and interfaces, because that’s where traction, stability, and “weight feel” intersect.

1) Think in energy: where does impact go?

Every step is an energy event. The mech drops mass into the ground, then redirects that energy into stabilization and forward motion. If you don’t show where energy goes, the mech reads like a puppet.

Concepting-side: pick one primary energy strategy for the leg.

A stiff industrial strategy: minimal visible compression, lots of thick structure, heavy “thunk” landings. This reads powerful but can feel harsh.

A suspended strategy: clear compression elements (pistons, shock struts, elastomer blocks) that visibly take load.

A compliant foot strategy: the foot itself flexes via segmented pads, toe splay, or heel cushions, while the leg stays relatively rigid.

Production-side: energy strategy affects rigging. Suspension-heavy designs want visible compression; compliant feet want toe and heel articulation; stiff designs want strong ankle motion and VFX impact cues to carry weight.

The best rule is simple: choose where the motion lives so you don’t demand it everywhere.

2) Shock vs rebound: two different reads

Shock is the absorption moment. Rebound is the release moment.

Shock reads as compression, settling, and a brief “pause” where the machine finds stability. Rebound reads as stored energy returning to motion—either a controlled push-off or a springy bounce.

Concepting-side: if you want a heavy mech, prioritize shock over rebound. Heavy machines settle; they don’t bounce. Rebound can exist, but it should look damped.

Production-side: shock and rebound are animation beats that can be standardized: plant → compress → settle → push. Even subtle versions of these beats sell mass.

Damping is the tone knob. High damping reads heavy, controlled, and stable. Low damping reads agile, energetic, and sometimes toy-like.

3) Toe and heel behaviors: how the foot “rolls” tells the story

Toe/heel behavior is the foot’s relationship to direction.

A heel-first plant reads like controlled deceleration and stability. A toe-first plant reads like speed, stealth, and climbing readiness. A flat plant reads like weight and industrial certainty.

Concepting-side: choose a default plant style that matches the role.

A siege or cargo mech often plants flat or heel-heavy.

A scout or striker often plants toe-first or mid-foot.

A rescue mech often plants flat with soft toe/heel transitions, suggesting controlled contact near humans.

Production-side: plant style can be used to standardize locomotion cycles. If the mech always plants heel-first, animation and IK can be more consistent. If it varies (toe-first on slopes, flat on level ground), you need clear design cues that justify that adaptability.

4) Foot families and what shock/toe/heel behaviors they naturally support

Different ground interfaces make different contact scripts feel believable.

A pad foot supports flat plants and controlled rolls. It can show shock through pad segmentation and slight ankle compression.

A hoof-like foot emphasizes toe/edge contact. It naturally reads toe-first and can show shock through split-hoof splay or heel cushioning.

A cleated foot reads like bite-and-set. The plant often includes a micro “dig” moment, which is a great shock cue.

A suction foot reads like press-to-seal and pop-to-release. Shock becomes the press and seal; rebound becomes the release.

A tracked assembly reads like continuous contact. Shock behavior moves from “foot roll” to suspension compression and track-ground deformation.

A wheeled interface reads like suspension and tire deformation. Toe/heel is less relevant; instead, you show weight through squat and rebound through suspension recovery.

If you try to animate a hoof like a tire or a track like a toe-roll foot, the design and motion will fight each other.

5) The contact script: plant, load, stabilize, release

A useful way to design and depict feet is to imagine a repeatable four-step script.

Plant: the first contact (heel, toe, or flat).

Load: compression and weight transfer.

Stabilize: a short “settle” as the mech centers mass.

Release: push-off, toe roll, or disengage.

Concepting-side: you can stage these as four thumbnails. The foot should look like it can hit each beat without breaking its own geometry.

Production-side: this script maps directly to animation and VFX triggers: contact decal, dust puff, compression, micro debris, and push-off kick.

A foot design that supports this script will feel grounded even in simple animations.

6) Shock design cues you can draw (without turning into engineering)

You can imply shock absorption with a few strong cues.

Visible struts or pistons near the ankle imply compression.

A telescoping collar implies vertical travel.

A stack of elastomer blocks or layered pads implies damping.

A floating heel plate implies a heel cushion.

A split toe implies splay and compliance.

Concepting: pick one cue and make it readable. Too many cues create mechanical confusion.

Production: keep compression travel believable. If the leg looks like it should compress 30 cm, but the rig compresses 2 cm, it will feel wrong. Design the travel to match what animation can deliver.

7) Rebound cues: how to show “controlled spring” without bounce

Rebound in heavy mechs should feel like controlled release, not a pogo stick.

Concepting: show rebound as a deliberate push through the toe or through the heel lifting, rather than a full-body bounce. If you want a more agile mech, you can exaggerate rebound slightly, but keep it damped.

Production: rebound can be sold by subtle body motion rather than dramatic foot motion. A small upward pelvis recovery after compression reads like suspension returning energy.

Also consider audio and VFX: a springy squeak reads light; a hydraulic hiss reads heavy; a dust burst at push-off reads strong.

8) Terrain changes the contact script

Terrain is the reality check. Different surfaces change how shock and toe/heel behavior should look.

On rock, you want firm contact and small slips. The foot may plant on edges; shock is sharp.

On mud, you want deeper compression and slower rebound. The foot sinks; release pulls suction.

On sand, you want broad contact and visible displacement. Toe push-off may throw sand.

On ice, you want cautious plants and less aggressive toe roll unless you have spikes. Rebound is minimal to avoid slip.

On metal decks, you want controlled friction and noise. A heel strike can be loud; a pad plant can be quiet.

Concepting: build terrain logic into the foot design. Spikes for ice, broad pads for sand, self-cleaning cleats for mud.

Production: terrain affects footstep VFX and sound. Your design should give those teams predictable “where the effect happens” zones.

9) Toe/heel behavior as traction strategy

Toe and heel are not just motion—they’re traction tools.

A strong heel can act as a brake: a heel spur, heel pad, or heel cleat can sell stopping power.

A strong toe can act as a drive: toe cleats, toe spikes, or a toe rocker can sell acceleration and climbing.

Concepting: if your mech needs dramatic stops, design a heel feature that looks like it can dig. If it needs explosive launches, design toe features that look like they can bite.

Production: braking and acceleration beats can be amplified with small changes in foot angle and compression timing. The design needs to support those angles without intersecting.

10) Tracks and wheels: where toe/heel becomes suspension language

Tracked and wheeled systems don’t “toe roll” like feet, but they still have shock and rebound.

Tracks show shock through road wheel compression, track deformation, and body squat. Rebound is the recovery of the suspension and the smoothing of motion after an obstacle.

Wheels show shock through suspension and tire deformation. Rebound can be a small oscillation if damping is low.

Concepting: if you want a tracked mech to feel heavy, show big suspension travel and slow recovery. If you want it to feel agile, show tighter travel and quick recovery.

Production: these decisions matter for physics and animation blending. A clearly designed suspension system sets expectations and helps teams implement consistent motion.

11) Camera and readability: sell weight with simple, repeatable beats

In many games, the player doesn’t see the foot close-up for long. Weight must be sold with macro motion and clear impact cues.

Concepting: prioritize big readable changes: heel-to-toe roll, visible compression, and a short settle. Avoid relying on micro toe joints that won’t read.

Production: standardize foot timing. If the mech’s step always includes a small settle, it will feel heavier. If it always rebounds quickly, it will feel lighter.

Impact VFX can do a lot, but it works best when the foot design provides clear contact faces and predictable edges.

12) A compact checklist for shock, rebound, and toe/heel behavior

Can you point to where compression happens (leg strut, ankle, foot pad segmentation)?

Does the design communicate a default plant style (heel, toe, flat) that matches the role?

Is rebound appropriately damped for the mech’s mass and tone?

Do toe and heel features support traction needs (brake vs drive vs climb)?

Does the contact face remain readable across camera distances?

Does the design support terrain logic (spikes, pads, cleats, seals) without becoming noisy?

Would the rig/animation budget realistically support the implied articulation?

If yes, the mech will feel grounded even with simple locomotion cycles.

13) Quick exercises to internalize the contact script

Pick one mech and draw four thumbnails of a step: plant, load, stabilize, release. Do it for two terrains (rock and mud). Then adjust only the foot design—add heel brake features, toe bite, and a visible shock cue—until both terrain versions feel plausible.

Then do a “damping sheet.” Draw the same step twice: once with high damping (heavy industrial) and once with low damping (agile). Notice how little you need to change: slightly deeper compression, slightly longer settle, slightly smaller rebound. That sensitivity is what makes mechs feel like mass interacting with terrain rather than animation cycles sliding across a plane.

When you design shock, rebound, and toe/heel behaviors as part of the ground interface, you aren’t just designing feet. You’re designing the mech’s relationship to gravity—and that’s what makes it feel real.