How to build a basic 3D version of the level with massing, metrics, composition, and iteration

Why build a blockout?

A blockout (also blockmesh or graybox) is a 3D rough draft level built with simple 3D shapes, but without any details or polished art assets.
The goal is to prototype, test, and adjust the foundational shapes of the level.
In the image below, notice the differences between the blockout version and the final shipped version. A shape might start as a gray block -- then after months of playtesting and art passing, the white block becomes a stack of barrels, the gray slab becomes a detailed wooden fence, etc.
comparison of blockout vs final art-pass for "Docks" in Call of Duty: Modern Warfare (2019) by Brian Baker
Blockouts support experimentation.
It is "cheap" to delete or rebuild some rough blockout geometry, but throwing away finalized art passed work is "expensive" and wasteful. When you are not confident about the level structure, it is best to keep it "cheap" until it is ready to become "expensive."
You can't playtest a design document or a layout sketch, but you can playtest a blockout and evaluate its flow, balance, encounter design, and metrics. This is the design phase when you finally begin to discover whether the ideas will work or not.

Key concepts

Before blocking out, you may want to learn about these concepts:
  • Massing is the general sense of volume and weight conveyed by the shapes.
    • Is this structure thick / heavy, or thin / light? What kind of place is this?
    • Landscapes need special consideration.
    • Composition is currently over-emphasized in level design culture today.
  • Metrics are the general scale, dimensions, and proportions of the level.
  • Lighting heavily affects how players perceive shape, depth, space, and mood.
    • Is that wall far away or close by? Is this room shallow or deep? Is it scary?
    • Some people do lighting later as part of an art pass, but we think earlier is better.
  • Wayfinding is the player's navigation process for learning the map structure.
    • How to help the player find the critical path / level exit? Does the player feel too lost?
  • Playtesting is when you run an experiment to see if the level meets its design goals.
    • Can most players complete the level? Do the encounters work? Is it balanced?
    • Playtesting is really important. This is the whole point of making a blockout.
example blockout video - "Uncharted: The Lost Legacy - Train Level Early Prototype" by Matthew Gallant

Construction methods

There are five common 3D level construction methods in games:
  • Primitives: arrange simple basic shapes like cubes and boxes.
  • Brushes / modeling: construct 3D shapes in the level editor.
  • Modular kit: connect pre-made pieces together, like Lego.
  • Sculpting: "paint" organic 3D shapes, useful for landscapes.
  • Splines: create math curves that procedurally generate geometry


Arrange boxes, move / rotate / scale them around. A very flexible and surprisingly powerful method. You can always use this method in any 3D engine or tool, but you'll hit limitations with blocking out anything beyond simple boxy buildings.
  • pay attention to metrics, establishing scale is tricky
  • to make a ramp: make a long wide thin cube, then rotate to slope downward.
    • to make stairs: avoid suffering and just make a ramp instead
  • to make a doorway: leave a gap between two walls, don't make a door frame
    • to make a window: make doorway-like gap, then fill in with a short waist-height wall
dimensional massing diagram by Francis Ching, from "Architecture: Form, Space, and Order"

Brushes / modeling

Brushes are simple low polygon 3D shapes modeled in the level editor. This was the main construction method across the industry from 1990s-2000s. We strongly recommend this method because it offers the most control and handmade feel, but unfortunately most modern game engines often have poor brush modeling tools. It can be tricky to figure this out.
  • use a brush-based 3D tool that emphasizes low poly geometry
  • use a big coarse grid size based on the player's width
    • Doom or Quake: 32u wide player = set grid to 32 or 64
    • Unity: 1m wide player = set grid to 1 or 2
    • Unreal: 60uu wide player = set grid to 50 or 100, or maybe 64 or 128
    • this all depends on your metrics!
simple 3D modeling with "brushes" in TrenchBroom; GIF demonstration by Benoit "Bal" Stordeur

Modular kit

Snap together pre-made pieces from a kit of modular parts. But if the kit is badly designed or poorly configured, it'll be hard to use. If you're new to 3D level design or 3D modeling, you can download a kit instead of making your own.
  • configure the Grid and turn on Grid Snapping (how-to: Unity, Unreal)
    • use a large coarse grid based on module size
    • e.g. if wall modules are 5m wide, then set grid to 5
  • use Vertex Snapping to align modules precisely (how-to: Unity, Unreal)
    • (1) select object, (2) change to Move tool, (3) hold V, (4) in 3D view, click and drag a vertex to another game object
For more on planning, measuring, and constructing modular kits, see Modular kit design.
For links to download free modular prototyping kits, see Resources.
"graybox" blockout modular kit used for prototyping levels in Skyrim, image by Joel Burgess


Most modern engines have a terrain sculpting tool. Be careful -- you'll be distracted by the power of sculpting and forget to do any level design! But if landscapes are central to the project, there's no way to avoid sculpting.
  • use a large brush size and focus on the big core shapes of the landscape
  • define ground planes with the Set Height (Unity) or Flatten Target (Unreal) brush
  • sculpt slopes as stepped terraces to define the gradient, then smooth it
  • avoid erosion and other auto-generator tools, you need control over the design
  • avoid spiky peaks and over-smoothed blobby mounds, two common beginner mistakes in sculpting terrain
For more on sculpting and designing terrain, see Landscape.
sculpting landscapes for the "Nagrand" region in World of Warcraft: Legion
Why not use a 3D art tool like Blender, Maya, Max, or SketchUp to blockout?
People debate this. Here's our take: 3D art tools don't let you tune gameplay, collision, encounters, or items. Playtests become slower and less frequent.
Example: on an unnamed AAA game, moving a rock requires a multi-step hour-long process: (1) load debug build, (2) find which file has the object, (3) open Maya, (4) edit file, (5) recompile game, (6) load debug build again to confirm change.


Splines are abstract curves that generate mesh along its path. They are a relatively recent construction method, becoming common only in the mid 2010s.
A spline is ideal for blocking out curvy linear forms like roads or rivers, where it can also automatically deform the surrounding landscape. It's also non-destructive; you can adjust a spline at any point and regenerate its geometry.
  • They require a lot of tooling, scripting, and art support; this investment makes sense for big large multi-year open world projects, but usually zero sense for smaller projects.
  • We don't recommend splines for beginners. Like sculpting, it offers a seductive illusion of speed and convenience. ("With enough splines, you could make the next Fortnite!") But in reality, splines are often a distraction from actually building and testing a level.
  • Not good for general blockouts / built environments. Currently, most level designers only use splines for landscapes or small specific parts of the blockout. Splines are good at defining lines, but not areas or volumes.
animated GIF of a procedurally generated bridge defined with a spline in Unreal Engine 4; by Peter Severud (via Artstation)

How to blockout

This is our recommended blockout process to give a sense of best practices and common problems. The example editor screenshots below use a brush-based method in the Quake level editor TrenchBroom.

1. Sketch layout

First, sketch a layout drawing. Even a simple 60 second scribble sketch is better than nothing.
It's difficult to blockout without any plan. Planning ahead means less wasted work later on. If the thought of blocking out a level gives you anxiety, then a layout drawing might help you work.
Some experienced designers blockout without a layout drawing, but don't be fooled -- they have enough experience to draw a mental layout in their mind. Improvisation requires experience, and if you don't have that experience, then there is no shame in planning.
Look at the layout sketches below. The left sketch emphasizes the scale of each space, the middle sketch focuses on the relationships between the areas, while the right sketch is a more detailed floor plan drawing. Any of these sketches can work, any of them can help you plan a blockout. Just draw something.
example: three similar but different layout drawing styles that can maybe help you plan the blockout... any of these are fine to get you started, JUST DRAW SOMETHING

2. Ground plane + scale figure

Create a ground plane at (0, 0, 0) in the center of the 3D space in the level editor. For more about ground planes, see Verticality.
Use a light-colored gridded prototyping texture (see Resources) so that you can visually estimate sizes and scales. This floor object will help "ground" the rest of the level geometry, providing a horizon line and context for everything else to rest upon.
Then add a placeholder player object / humanoid scale figure to establish your sense of scale. If you don't have any humanoid assets, create a roughly human-shaped block to serve as a placeholder; see Metrics for common humanoid sizes. The scale figure helps establish consistency and clearance for the player.
When working with a modular kit, scale figures are less important because the world scale has already been factored into the module design.
example: a gray ground plane with a yellow scale figure standing on it

3. Build a wall

Build a wall segment that's approximately 150-200% as tall as the scale figure.
If you're working in a modern game engine, sizes don't have to be exact -- the sense of proportion is most important to establish here. Or if you are blocking out with a modular kit, just place a standard wall module next to the figure.
Texture the wall with a different color from the ground plane. Color and brightness provide important context for understanding what the space is made of, and how these various floor and wall planes relate to each other. If you are afraid of colors affecting your blockout too much, then at least use textures with different shades of gray.
For more on common hallway / wall sizes and humanoid dimensions, see Metrics.
example: added a white wall segment that's twice the height of the scale figure

4. Duplicate walls

Clone / copy-and-paste / duplicate the wall segments to build up more space until you have at least one room or hallway. Duplicate or drag-clone (in Hammer, hold Shift and drag the brush; in UE4, hold Ctrl+Shift and drag the wall object) for fast construction.
Intersections are OK. It's OK to be a bit messy. The edges don't have to align perfectly.
If you want a doorway or window, just leave a gap between wall segments, and fill it in later. Entryways and hallways should be at least twice as wide as the scale figure.
example: copy-and-pasted / duplicated more wall segments, based on the first wall

5. Playtest

Any sculptor or 3D modeler will tell you that the most important thing to do is to keep viewing your model from different angles. In blockout, the best way to do that is to actually walk around the space and playtest; flying around in the 3D editor view isn't enough because you need gravity, collision, and movement speed to assess scale and clearance.
Does this half-built space feel big enough? Does it feel too open, or too closed? What kind of feeling or resemblance were you aiming for, and are you on track to achieving it?
example GIF: walking around the half-built space in the game engine, playtesting as soon as possible

6. Expand blockout

You can blockout an entire building with a single cube. If it's a side area, don't waste your time building the interior yet. At this early stage, you don't even know whether the building is the correct size, or if you'll delete the entire building later on. Resist the urge to add detail.
Focus on boundaries and core shapes / massing. Omit details.
Keep duplicating more scale figures as you expand the space
Add new ground planes and verticality as necessary, but avoid building stairs... instead, use ramps
Notice how the construction is kinda loose and messy... let it be loose and messy
example: following a layout sketch, more areas blocked out with more scale figures

7. Playtest again

Remember, the strength of the blockout vs the layout is that you can actually test the blockout. Don't squander this strength -- keep playtesting in-game!
As you prototype new areas and walk around in them, ask yourself:
  • Do the new areas feel too small or too big? Does it take a really long time to cross the room?
  • Does each room feel too cramped or too open?
  • Is it difficult to walk from one area to another? What type of flow did you intend?
  • Are there any corners or intersections where you get stuck?
example GIF: walking around the new areas, playtesting as we build

8. Diverge

The point of playtesting is to check your plan against reality, and 99% of the time, your plan will not survive a playtest unscathed. Chances are, many rooms will feel too awkward, doorways too narrow, the layout too confusing.
But this is exactly why we blockout! We can freely diverge our plan in response to the playtest, with minimal waste or fuss. Rearrange walls, lengthen or shorten hallways, rethink what is possible. Want to rebuild huge sections of your blockout? Go for it. Want to delete an entire room? Do it. Need to split a courtyard into two smaller areas? You have permission. Keep an open mind about what your playtests and walk arounds are telling you and stay flexible.
(Why bother with a layout sketch if we're just going to ignore it eventually? Well, our initial layout sketch helped us combat "blank page syndrome" and get started, but now our map has outgrown it. Thank the sketch for its service, and now, let it go.)
example GIF: the original blockout felt too cramped, so what if we widened the space and deleted the walls?

9. Iterate

Keep an open mind and continue this cycle of modification + playtesting. Continue developing the blockout. Build, then walk around in it, then modify, then playtest again... and repeat. This design process is called iteration, because we are making new iterations that build off of the strengths of the previous version.
As you gradually build more and more of the level, it may surprise you how much it changes over time. Let the map surprise you.

Common blockout problems

  • (most common) My blockout feels too small / too big.
    • Use more scale figures during construction.
    • Playtest more often and catch scaling problems sooner.
    • Too big? Delete unnecessary rooms and compress what's left.
    • Too small? First expand the outward boundary to give yourself more space, then expand / space-out the areas closer to the center. This is more labor intensive than fixing a "too big" problem.
    • If all else fails, delete and rebuild. This time, measure more. Pay attention to metrics.
  • I keep flying around the 3D view and never building anything.
    • That's OK, you're actually evaluating the sense of space. It's not actually a problem.
    • ... but if you fly for 10+ minutes, then maybe you're procrastinating.
      • Keep a to-do list of tasks, and return to that list often.
      • Do something else and return to the blockout later.
  • I have anxiety and stare at the empty level editor screen without making anything.
    • Sketch a layout drawing, and then try to follow that plan.
    • Just blockout one simple room. You can always delete it later. The point is to get rid of the blank page. In drawing, this is "activating the canvas"; in writing, this is a "shitty first draft."
    • Do something else and return to the blockout later.

Example blockouts

"Castle" for Dirty Bomb (Splash Damage)

layout, blockout, and final version of Castle for Dirty Bomb, by Splash Damage ("Blocktober: Dirty Bomb")
Splash Damage level designer Anthony "MassE" Massey designed the map Castle for the competitive multiplayer team shooter Dirty Bomb. Massey took inspiration from twisting medieval streets and typology of the real-life Tower of London, and conceptualized the initial layout drawing (above, left). But note how the resulting blockout (above, center) differs from the layout with fewer curves, more 90 degree angles, and chunkier areas. The layout was just an initial guide. Because this is a multiplayer shooter map, the design team playtested the blockout with a focus on movement and combat metrics:
“The scale of maps is always the hardest aspect to get right. It’s important to plot your main paths and measure these distances; we’re looking for anything between 8 and 12 seconds from spawning to an objective. [...] Anything longer than that and players get frustrated when they respawn and have to run back. On the other hand, if the time is shorter it risks the map feeling too small for 8v8 matches, and can lead to chaotic gameplay. [...] This stage is crucial to map development, but our team operated by a simple rule of thumb; if it feels long, it’s too long."
"Considering [player classes] is the next step. We had to look at combat ranges to allows our entire arsenal to function, [...] while also ensuring variety in combat spaces to allow [different abilities] to be viable (like [an airstrike ability]). In real terms, this means considering the ratio between outdoor and indoor areas, ensuring [characters with outdoor-focused abilities] were viable."

"World's Edge" for Apex Legends (Respawn)

final detailed blockout (left) and final art pass (right) for "World's Edge" map in Apex Legends; blockout by Rodney Reece
Respawn level designer Rodney Reece built the blockout for "World's Edge", a large competitive multiplayer map for first person battle royale game Apex Legends. Notice how the map changed drastically from blockout (left) to art pass (right) in not only theme but also layout and composition.
"Originally the idea was the map was snowy. But art wanted to bring green into the map, and in one of the meetings, Robert Taube suggested what if the Epicenter (then called Frozen Explosion) caused the snow.
A key to being a good designer is being flexible to new ideas. For instance, the Art team came up with The Dome. In my blockmesh, it was a volcano. They pitched it and I adjusted to incorporate the idea. I had to create a new layout for it, but it made it better.
But other times, certain [points of interest] are fun from the beginning. In those situations, I am more stubborn about what can change. Sorting Factory is a good example of that. It's important to identify what's precious and what's flexible in terms of layout. Because it takes a team!"

Against blockouts?

For some projects, the traditional blockout might be less helpful. The experience may depend less on spatial design and more on the art pass. Blockouts can't validate a concept dependent on art or other assets.

Vertical slice for "Firewatch" (Campo Santo)

For the first person narrative exploration game Firewatch (2016), developer Campo Santo wanted to focus on mechanics like walking and talking; the main appeal of the game concept was looking at art passed scenery and listening to voice acted dialogue. Following typical best practices, they first built a blockout to test the viability of these mechanics. However, the blockout did not help them answer any questions about the player experience because the game pacing was fundamentally a narrative design and environment art issue, not so much a level design issue. The traditional blockout process wasn't working.
According to environment artist Jane Ng's account, it wasn't clear whether Firewatch would "work" as an experience until they skipped the blockout process and instead completed a vertical slice prototype with an art passed environment and near-final dialogue.
"Greyboxing did not answer any of the important questions" and other slides from "Making the World of Firewatch" by Jane Ng at GDC 2016

Location scouting for "Untitled Goose Game" (House House)

For the top-down third person stealth puzzle game Untitled Goose Game, developer House House sought to create an authentic-feeling British village in 3D. Level designer Jake Strasser had never been in the UK, so blocked out the initial level with occasional use of photo reference. However, this blockout-first approach required Strasser to fill-in gaps from his imagination -- and because he didn't have a British imagination, these gaps often felt implausible or inauthentic in subtle ways, counter to their intent. The traditional blockout process wasn't working.
So instead, Strasser tried a research-first "location scouting" approach. He went on an exhaustive virtual tour of various UK villages, taking lots of photos from Google Street View. After recreating several village streets in-game, Strasser finally pin-pointed what type of structure suited the game's needs, and settled on an unusual side street layout based on Pump Street in the village of Orford. Here, blockout was less about building a space, and more about discovering a space.
"It started feeling more like a unique place with its own quirks and history"... from "Google Maps, Not Grayboxes: Digital Location Scouting for Untitled Goose Game" for GDC 2021 by Jake Strasser

To review

A blockout is a simple but playable "rough draft" level with minimal detail. We keep it simple and blocky so that we can easily change it.
You can build a blockout with primitives, brushes, modular kit, sculpting, or splines. The best technique will depend on your engine and project, or combine multiple techniques.
How to blockout:
  1. 1.
    Sketch a layout, even a simple one
  2. 2.
    Add a ground plane and a scale figure (probably an adult humanoid)
  3. 3.
    Add a wall, at least 150-200% taller than the scale figure
  4. 4.
    Duplicate walls to make a room
  5. 5.
    Playtest immediately; does it feel OK to walk around the room? You need to know now.
  6. 6.
    Expand the blockout, build more rooms, add more scale figures
  7. 7.
    Playtest again
  8. 8.
    Diverge from your original layout plan
  9. 9.
    Iterate! Keep playtesting, then editing, then playtesting, etc.
The most common problem is scale, especially for beginners. Playtesting the blockout in-game is the only way to know if it feels too big or too small.
Blockouts might be less helpful for some projects like single player narrative levels. You should still blockout, but just spend less time on it.

Now what?

More about blockouts

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On this page
Why build a blockout?
Key concepts
Construction methods
Brushes / modeling
Modular kit
How to blockout
1. Sketch layout
2. Ground plane + scale figure
3. Build a wall
4. Duplicate walls
5. Playtest
6. Expand blockout
7. Playtest again
8. Diverge
9. Iterate
Common blockout problems
Example blockouts
"Castle" for Dirty Bomb (Splash Damage)
"World's Edge" for Apex Legends (Respawn)
Against blockouts?
Vertical slice for "Firewatch" (Campo Santo)
Location scouting for "Untitled Goose Game" (House House)
To review
Now what?
More about blockouts