Chapter 4: Chassis & Packaging

Created by Sarah Choi (prompt writer using ChatGPT)

Chassis & Packaging for Vehicle Concept Artists — Mechanics & Function 101

A vehicle’s chassis is its skeleton and nervous system: it carries loads, defines safety envelopes, and dictates where everything else can live. Packaging is the choreography that fits power source, driveline, suspension, occupants, cargo, tanks, and electronics into that skeleton without lying to physics or breaking the silhouette. For vehicle concept artists—on both the concepting and production sides across indie and AAA—understanding chassis types and packaging logic is how you turn a sketch into something modeling, rigging, physics, VFX, audio, and UI can execute with minimal rework.

Chassis choice begins with locomotion and structure. A monocoque (unibody) integrates body and frame into a single load‑bearing shell; it enables tight packaging, low weight, and high torsional stiffness with carefully placed stampings and reinforcements. A body‑on‑frame uses a separate ladder or perimeter frame with a bolted body on top; it trades weight and height for modularity, durability, and easier repairs. Spaceframes and tubs (composite or metallic) sit between: a lattice or closed tub provides stiffness, with bolt‑on subframes for suspension and powertrains. Each chassis implies different silhouettes, floor heights, door apertures, and crash behavior; drawing them honestly makes proportion decisions feel inevitable instead of arbitrary.

Monocoques favor low floors, smooth underbodies, and precise crash management. The roof, sills, pillars, and floor pan work together as a stress skin; cutaways should show load paths from suspension towers into sills and cross‑members. Monocoques excel for road cars, light EVs, and aircraft fuselage analogs because they package batteries or fuel along the floor and integrate mounts directly into stampings. The cost is modularity: major changes require re‑engineering stampings, so variant planning must happen early. Production‑side callouts should lock sill thickness, tunnel or tray depths, and tower positions so modelers can build shells that behave as implied.

Body‑on‑frame designs raise floors and simplify variant building. A ladder frame carries engines, tanks, winches, and tow points; the body becomes a weather shell. This is ideal for off‑roaders, utility, heavy cargo, and armored roles. You can swap bodies without redesigning the frame, and you can stretch wheelbases or add axles with consistent interfaces. The silhouette reveals exposed frame rails, higher ride height, and clear daylight between underbody and ground. In callouts, show chassis rails, cross‑members, and cab/bed mount bushings; in exploded views, reveal body mounts and hardpoint patterns that enable quick skews and special variants.

Spaceframes and tubs are stiffness‑first solutions for high performance or weight‑critical builds. A triangulated frame or composite tub takes roll cage logic seriously; hardpoints for suspension and belts sit on nodes rather than thin skins. This permits large cutouts for doors and canopies without losing stiffness. The silhouette reads as thin‑walled but strong; interior packaging becomes tight and tailored. Production sheets must identify node coordinates, tube diameters, laminate thickness, and bonded insert locations to avoid later contradictions in rigging and physics.

Packaging starts with occupants, because people are the least flexible component. Set a driver eye‑point, hip point (H‑point), and reach arcs that respect control placement and sightlines. In two‑up or four‑up layouts, stagger footwells and tunnel or tray heights so knees clear consoles and battery sills. Canopy frames and pillars must not occlude critical FOV; in cockpit views, the dash depth and pillar thickness should leave predictable UI zones. Door apertures, step heights, and handholds are part of readability and animation; paintovers should show ingress/egress poses and hinge arcs so animators can rig without changing geometry later. In utility and troop carriers, bench and stretcher standards drive interior width and door clearances; your orthos should carry those numbers prominently.

Cargo comes next because it competes with the same volume as occupants and powertrains. Decide between length priority (beds, racks), height priority (stacked crates, mechs), and mass priority (dense batteries, fuel, ammo). In road vehicles, wheelhouses and suspension intrusions eat cargo width; show those early. In aircraft and VTOL, CG movement with load/unload is critical; locate cargo floors near the vehicle’s roll/pitch centers or mandate load limits forward and aft. Side doors, tailgates, ramps, and cranes must clear ground at expected angles; callouts should include ramp length, breakover, and deploy arcs. The silhouette should read load‑capable via straight upper rails, reinforced sills, and exposed tie‑down hardpoints.

Hardpoints are where structure meets systems. Suspension pick‑ups, engine or motor mounts, steering racks, battery or tank saddles, seat belt anchors, hinge posts, tow hooks, winches, weapon or sensor pylons, and roof racks all need reinforced nodes with repeatable patterns. In concept, show their existence with plate thickness, gussets, or boss geometry; in production, label them with coordinates and interface types (bolt circle, dovetail, quick‑release). Define no‑drill zones for safety (airbags, high‑voltage, fuel), and provide generic adapters for live‑ops skins and cosmetics to attach without violating structure. A consistent hardpoint language across a faction enables kit reuse and speeds variant creation.

Power source selection reshapes packaging but not the logic. ICE layouts put big masses up front or mid‑ship and require generous cooling, exhaust routing, and transmission tunnels; monocoques must make towers and tunnels part of the stiffness story. EV skateboards flatten floors and lower CG; the pack becomes a structural tray tied into sills and cross‑members, and e‑axles reduce tunnel needs but add inverter and junction boxes near axles. Hybrids crowd space; you must pre‑reserve stack volumes for engine, motor, gearbox, and batteries so service access remains possible. Fuel‑cell stacks want straight tank runs and humidifier air paths; fusion or anti‑grav fiction should express reactor shields or emitter rings as major structural volumes with clear keep‑out zones. Cutaways must make these truths visible; orthos must freeze critical heights and widths so teams can route lines and ducts.

Crash and survivability envelopes are non‑negotiable. Front and rear crumple zones, side‑impact rails, rollover strength, and intrusion limits around occupants and tanks must be designed and labeled. On EVs, underfloor packs require skid plates, crush cones, and standoffs to protect against rocks and curbs; in body‑on‑frame, outriggers and sill rails carry side loads around cabins. In aircraft/VTOL analogs, landing loads and roll‑over protection define hoop structures and keel beams; show these beams in silhouette so the exterior read matches resilience. Damage states should respect these structures: break lines follow panel seams while frames bend at designed nodes, preserving a readable, safe cavity around occupants in gameplay.

Serviceability is packaging’s reality check. Filters, pumps, coolant bleed points, brake reservoirs, fuse boxes, and charging/refuelling ports need tool clearance and human reach. In callouts, draw the door that reveals them and the hand path that operates them. On EVs, show pack drop procedures and jack points; on off‑roaders, show how winches pull straight along frame rails; on aircraft, show avionics bays and quick‑release panels. If your design implies a one‑piece clamshell, offer an alternate service hatch for routine tasks so animation and rigging have a believable everyday state.

Underbody and aero surfaces are both structure and readability. Skid plates, diffuser tunnels, battery shields, and frame cross‑members must coexist and be drawn as layered plates with fastener logic. These choices affect ground clearance, approach/departure/breakover angles, and silhouette. In AAA, LODs should retain key underbody masses that explain dust trails and scrape VFX; in indie, a single underbody sheet with arrows for airflow and force paths may suffice.

Camera‑read planning makes packaging visible where it matters. Chase cams compress height and emphasize plan view; your silhouettes should keep chassis rails, sills, and wheel arch daylights readable at distance. Cockpit cams punish pillar thickness and dash depth; plan UI dead‑zones into the structure and test with screenshots at target FOVs. For VTOL/hover, top‑down views expose arm, boom, and ring structures; ensure negative spaces between emitters and hull remain clean when gear deploys.

Deliverables that unblock teams bundle chassis truth into shareable artifacts. A metrics & chassis sheet fixes wheelbase, track, overall length/width/height, floor height, sill thickness, tunnel/tray depths, tower positions, and CG estimates. Orthos show outer shell and inner frames together with datum marks. Cutaways reveal beams, tubs, packs, tanks, and subframes with arrows for load paths and cooling. Exploded views separate frame, body mounts, suspension cradles, and panels with fastener and bushing logic. Callouts bind coordinates to hardpoints, hinge arcs, jack points, and keep‑out zones (airbags, HV, fuel). A camera‑read board captures chase, cockpit, and top‑down views under representative lighting.

Indie and AAA cadence differ in granularity. Indie teams often merge these into one evolving canvas: side ortho with inner frame lines, a quick cutaway, and two callout clusters that prove service access and crash logic. AAA teams separate gates: structure lock (frame/tub definition), packaging lock (powertrain/occupant/cargo), modeling kickoff (orthos + callouts), rigging check (exploded), camera‑read sign‑off (distance boards), and optimization (LOD underbody + panel seam alignment). In both contexts, consistent naming, scales, and change logs prevent drift across variants and skins.

From the concept seat, success means selling truth with silhouette: when the exterior implies a stiff spine, a low tray, or a ladder rail, the cutaway confirms it. From the production seat, success means unambiguous coordinates and serviceable assemblies. When chassis type, occupant geometry, cargo volume, and hardpoints are coherent on paper, every department can move without guesswork. That coherence is the difference between a pretty picture and a vehicle that feels inevitable to build—and unforgettable to drive.