Gym levels and metrics maps

A gym level (also called a metrics map, metrics zoo or metrics playground) is a developer-only test map full of measured examples: doors of several widths, stairs of several step heights, jumps of increasing length, ledges, slopes and cover at fixed sizes. You walk the default character through it to learn what the player can and cannot do, before anyone builds a real level.

The Level Design Book recommends building a "'metrics zoo' / 'metrics playground' developer-only test map that exhibits the different gameplay objects, modules, and prefabs across all your levels" (The Level Design Book: Metrics).

#Purpose of a gym level

Metrics on paper stay untested until you try them through the game camera. The Level Design Book's process is to "make a simple level with various rooms, hallways, and floor heights", then "walk around with gravity, jump on objects, be a general nuisance", paying "special attention to the sizes of walls, doors, and floors" (The Level Design Book: Metrics). It asks two useful questions: "Does the height of the stair steps feel right?" and "Do doors feel too narrow or too short?" (The Level Design Book: Metrics). Then: "After each metrics revision, playtest and walk through again. Repeat." (The Level Design Book: Metrics).

The gym then becomes reference. Robin-Yann Storm's talk title states the principle: "Your documentation should be in-game", in gyms, zoos and museums (YouTube: Gyms, Zoos, and Museums: Your documentation…). A level designer unsure about a ledge height can walk to the gym and try it.

#What goes in a gym

A gym tests the player's movement against the collision capsule and the movement settings. A useful layout is a row of test lanes, each varying one number:

The settings are real ones: Unity's CharacterController steps up a stair "only if it is closer to the ground than" its Step Offset, and only climbs slopes less steep than its Slope Limit (Unity Manual: Character Controller component reference). Godot's CharacterBody3D treats slopes up to its floor_max_angle, 45 degrees by default, as floor (Godot Engine: CharacterBody3D). Unreal's Character Movement component has a Max Step Height ("Maximum height character can step up") and a Walkable Floor Angle (Unreal Engine Python API documentation: unreal.CharacterMovementComponent).

#Gyms, showcase maps and zoos

Teams use the names loosely. A useful split:

• A gym or metrics map tests the player's movement and the level's building metrics (The Level Design Book: Metrics).
• A showcase (warehouse) map lays out every art asset or material to check consistency.
• A zoo of gameplay objects shows every enemy, pickup or interactive object; The Level Design Book's "metrics zoo" mixes the first and third ideas (The Level Design Book: Metrics).

Storm's title names gyms, zoos and museums together as in-game documentation (YouTube: Gyms, Zoos, and Museums: Your documentation…).

#Related terms

grids and metrics · player collision capsule · blockout · showcase (warehouse) map · playtesting spaces · affordance

#Further reading and watching