Grids and metrics

Metrics are the measurements a game is built around: how big the player is, how high they can jump, how wide a door or corridor has to be. A grid is the snapping increment you build on so that every piece respects those measurements. The Level Design Book defines metrics as "the sense of scale, distance, and measurements across the entire level / game" (The Level Design Book: Metrics).

When these numbers are set early, the blockout, the modular kit and the final art all line up. Errors found late are expensive, because moving a wall can mean rebuilding a room.

#Player metrics and building metrics

The Level Design Book splits metrics into two kinds (The Level Design Book: Metrics):

• Player metrics are facts measured from the engine: the player's collision size, eye height, jump height, walk and run speed.
• Building metrics are guidelines designers choose: floor heights, wall thickness, door sizes, room proportions.

Player metrics are discovered; building metrics are decided. A team should write both down in one place and treat them as a contract between design and art. See level design and environment art.

#Engine defaults compared

Different engines measure in different units and ship with different default player sizes. The table collects The Level Design Book's starting values (The Level Design Book: Metrics).

The table shows two things. First, game doors are much bigger than real doors: a Source door of 56 × 112 units is roughly 1.4 × 2.8 m if you read units as inches, against a real US door of 36 × 80 in (about 0.9 × 2 m). Second, the "unit" itself is fuzzy. The book notes that Quake's inches "don't really make sense" (The Level Design Book: Metrics), and older Unreal games used other conventions: Epic's UDK documentation says 1 unit was 2 cm in Unreal Tournament, while "most licensees use a scale of 1 Unreal Unit to 1 cm" (Unreal Developer Network: Unreal Units). See units, scale and axes.

#Grids: choosing a snap size

A grid applies the metrics to every piece. If every wall piece is a multiple of the grid, everything snaps together without gaps.

The Level Design Book observes that Source and older engines used power-of-two grids (8, 16, 32, 64…), that Unity users often prefer 1s and 10s, and that Unreal users are split by age; its advice is to use whatever rounding you and your collaborators prefer (The Level Design Book: Metrics). World of Level Design blocks out CS:GO maps on a 16- or 32-unit grid (World of Level Design: CS:GO SDK Player and Architecture Scale…).

On a 2026 Polycount thread about modular interiors, artists recommended coarse snaps. One suggested "0.5m is probably the minimum snap distance, but I would keep it to 1m if possible", because small snaps make misalignment easy to miss; another advised the largest value you can get away with (Polycount: Building modular interiors question!). Joel Burgess makes the same point for Skyrim: level designers usually snapped to half the kit's footprint, and larger snap sizes made misalignment easier to spot (Game Developer: Skyrim's Modular Approach to Level Design).

#Gameplay metrics: jump, climb and cover

Building metrics have to respect what the player can do. Emilia Schatz describes Uncharted's rules: Nathan Drake could climb to a ledge 3.5 m above him, so no ledge was built between 3.25 m and 4 m; walkable slopes stayed under 35 degrees with nothing between 30 and 45; and low cover was 0.9–1.25 m tall with a 0.5 m buffer around it (80 Level: Defining Environment Language for Video Games). "There cannot be any middle ground" (80 Level: Defining Environment Language for Video Games). The buffer zones are as important as the numbers themselves. See affordance.

Other metrics worth writing down before you build:

• Corridor width. The Level Design Book says hallways should be at least double the player's width (The Level Design Book: Metrics). Burgess set the narrowest traversable space in Skyrim kits at a minimum of two character widths, so two AI characters can pass each other (Game Developer: Skyrim's Modular Approach to Level Design).
• Stairs. The Level Design Book suggests a landing every 12–16 steps and a slope of 30–35 degrees (The Level Design Book: Metrics).
• Slopes for AI. Burgess gives roughly 60 degrees as Skyrim's maximum AI incline, while noting designers may prefer 30–45 degrees for animation (Game Developer: Skyrim's Modular Approach to Level Design).
• Combat ranges. A community analysis quoted by The Level Design Book puts Team Fortress 2's close-range weapons at 256 units or less, medium range at up to 1024, rockets and snipers at around 2048, and the largest drop without fall damage at 256 (The Level Design Book: Metrics).
• Door frames. Burgess recommends one uniform door frame size across all kits, so any kit can connect to any other (Game Developer: Skyrim's Modular Approach to Level Design).

#Grids in the art pipeline

Metrics also affect every environment asset:

• Modeling. Set your modeling software's grid to match the engine's snap. A wall modeled 3.98 m long will leave a visible seam on a 4 m grid. See units, scale and axes and pivot point.
• Pivots. Put the pivot on a grid corner so pieces snap predictably. Burgess lists "pivot point location, base footprint size, and transition metrics" among the things that are very costly to change late in production (80 Level: Building Huge Open Worlds: Modularity, Kits &…). See modular kits.
• Floor thickness. Burgess advises deciding floor thickness in advance to avoid co-planar surfaces and Z-fighting (Game Developer: Skyrim's Modular Approach to Level Design). The Level Design Book's stack test asks the same: floors "should NOT be paper thin" (The Level Design Book: Modular kit design).
• Texturing. The Level Design Book recommends world-aligned grid or checker textures in the blockout to judge distances, and keeping texture scale independent of object scale, using world-aligned or triplanar mapping in modern engines (The Level Design Book: Metrics). See checker maps.

#In different tools

• Unreal Engine works in centimetres; the editor's snap sizes are set in the viewport toolbar. See level editors and blockout tools.
• Unity works in metres; Unity users often prefer round numbers in 1s and 10s (The Level Design Book: Metrics).
• Source / Hammer uses power-of-two units, with the [ and ] keys changing grid size (World of Level Design: CS:GO SDK Player and Architecture Scale…).
• Blender, Maya, 3ds Max let you set scene units and grid subdivisions to match the engine. See units, scale and axes and modeling software.

#Further reading and watching