Blockout (greyboxing)

A blockout (also called a greybox) is a playable rough draft of a level, built from simple shapes. Epic's documentation describes greyboxing as "making a playable rough draft of a level to get a sense of its gameplay before polishing its look" (Epic Developer Community documentation: Greyboxing in Unreal Editor for Fortnite). World of Level Design describes it as "using primitive geometric shapes to block-out your level or environments" (World of Level Design: Blockouts in UE5).

A blockout lets you find problems while they are cheap to fix. Moving a grey box takes seconds; moving a finished, lit, textured building takes days.

The Level Design Book defines a blockout as "a 3D rough draft level built with simple 3D shapes, but without any details or polished art assets" (The Level Design Book: Blockout). It gives two main reasons to build one: blockouts "support experimentation", and, unlike a design document, "you can playtest a blockout" (The Level Design Book: Blockout).

#What a blockout is for

• Layout and scale. Epic recommends testing scale and layout before level design proper, and scaling blocks "to the size of the buildings and props you plan to use" (Epic Developer Community documentation: Greyboxing in Unreal Editor for Fortnite).
• Finding problems early. "Greyboxing helps you identify issues before building your level and adding gameplay mechanics" (Epic Developer Community documentation: Greyboxing in Unreal Editor for Fortnite).
• Gameplay prototyping. A blockout lets you test movement, combat spaces, sightlines and flow (World of Level Design: Blockouts in UE5).
• A contract for art. Environment artists are often handed a "rough, simplistic blockout by level design which you have to stick to" (80 Level: Environment Design: Modularity, Color &…). The blockout defines the spaces the art must fill. See level design and environment art.

• Early material tests. Epic notes material artists can test textures on greyboxed assets (Epic Developer Community documentation: Greyboxing in Unreal Editor for Fortnite).

#How to build one

The workflow is similar across engines; see level editors and blockout tools for the tools themselves.

1. Start with big masses. Rooms, buildings, terrain heights, main paths. World of Level Design advises using "large modular pieces first" (World of Level Design: Blockouts in UE5); see modular kits.
2. Work to metrics. Use your character's movement numbers (jump height, climb height, corridor width) from day one. See grids and metrics and units, scale and axes.
3. Colour-code, don't texture. Epic suggests colouring blocks so elements are easy to tell apart (Epic Developer Community documentation: Greyboxing in Unreal Editor for Fortnite). A typical scheme: one colour for walkable floors, one for climbable surfaces, one for cover, one for out-of-bounds.
4. Play it. Epic: "Consider the first pass of your level your blockout, then iterate" (Epic Developer Community documentation: Greyboxing in Unreal Editor for Fortnite).
5. Only then add art. "Add props and art once you are happy with how the level plays" (Epic Developer Community documentation: Greyboxing in Unreal Editor for Fortnite).

Open worlds follow the same order at a larger scale. On The Witcher 3, layouts started as grey boxes that were then replaced with final meshes, decorations, paths and foliage, and story changes could still send an area back for rework (80 Level: World Building of Witcher 3).

#In different tools

• Unreal Engine 5: World of Level Design calls Modeling Mode "your primary way to blockout in UE5", noting that BSP brushes are deprecated but still available (World of Level Design: Blockouts in UE5). Switching Modeling Mode's output to Dynamic Mesh keeps shapes inside the level, which the author uses "all the time for blockouts" (World of Level Design: Blockouts in UE5).
• UEFN (Unreal Editor for Fortnite): Epic's workflow uses shape tools to drag out blocks, cylinders and discs, the Merge tool to combine them, and attribute tools to colour them (Epic Developer Community documentation: Greyboxing in Unreal Editor for Fortnite).
• Other engines and DCC tools: see level editors and blockout tools and modeling software for Unity, Godot, Blender and others.

#Metrics in the blockout

A blockout only tests something if its dimensions match the game. Emilia Schatz describes creating "rough blockout geometry to define the shape of our spaces" at Naughty Dog, with strict rules that no edge sits in an ambiguous range (80 Level: Defining Environment Language for Video Games).

Epic's checklist is a good minimum: vehicles fit through spaces meant for driving, platforms sit at heights players can reach, and no spaces are boring or over-accessorised (Epic Developer Community documentation: Greyboxing in Unreal Editor for Fortnite).

#Playtesting the blockout

Play your blockout yourself after every major change, then watch others play it. Things to look for:

• Where players hesitate, backtrack or get lost (a wayfinding problem).
• Where they miss the intended route or a key object (a focal point or landmarks problem).
• Whether combat spaces give enough cover and enough exits.
• How long sections take compared with your plan.

Expect big changes. Andreas Lohse's portfolio blockout "quickly changed throughout the first week from a larger alley scene to something more narrow" (80 Level: Get Away: Lighting & Composition in…). Changes of this size are normal at the blockout stage.

#Lighting the blockout

#Common problems

• Detailing too early. Once something looks nice, people are reluctant to move it. Keep it grey until the layout is stable (Epic Developer Community documentation: Greyboxing in Unreal Editor for Fortnite; World of Level Design: Blockouts in UE5).
• Wrong scale. The Level Design Book calls a level that "feels too small or too big" the most common blockout problem. Its fixes: "Use more scale figures during construction" and "Playtest more often and catch scaling problems sooner" (The Level Design Book: Blockout).
• Staring at an empty editor. Sketch a layout or block out one simple room first; the book calls this "activating the canvas" (The Level Design Book: Blockout).
• Overattachment. If a blockout isn't working, the book's advice is blunt: "delete everything and rebuild. It's just a blockout" (The Level Design Book: Blockout).
• Paper-thin floors and missing glue pieces. For modular blockouts, the book recommends floors with real thickness and enough "glue" pieces to join kits at angles; it calls collision "one of the biggest issues" (The Level Design Book: Modular kit design).
• Ambiguous geometry. Ledges and slopes in the "maybe" range confuse players and get worse after the art pass (80 Level: Defining Environment Language for Video Games).
• Boring or over-accessorised spaces. Epic names both as things to test for (Epic Developer Community documentation: Greyboxing in Unreal Editor for Fortnite).
• File housekeeping. In UE5, Modeling Mode can create many unused static meshes and a bloated folder; dynamic-mesh blockouts live only in the level, so save the map (World of Level Design: Blockouts in UE5).
• No one from art involved. A layout locked without an artist's input may be hard to make beautiful later (80 Level: Environment Design: Modularity, Color &…). In Karlsson and colleagues' study, a creative director said artists "are afraid of changing the white-boxed layout they received from the level designers" (Karlsson et al. 2023). Agree early which parts of the blockout art may move.
• Polishing a test level. Steve Lee spent several weeks on the Unreal Engine 3 test level that got him onto BioShock Infinite's level design team, and later advised aspiring designers not to overwork such tests or set needlessly high standards (YouTube: The Unreal level I made to work on Bioshock…; Game World Observer: Lessons learned from building test level for…). He put verticality and combat ahead of visual polish and architectural accuracy (Game World Observer: Lessons learned from building test level for…).

#Further reading and watching