Summary
3D blocking, often called greyboxing, is the practice of building a playable level from simple shapes before making final art. The aim is to answer design questions quickly: can the player move through the space, read the goal, understand scale, use the camera, and interact with the intended objects?
In a student project, a good greybox is more valuable than a beautiful but untested room. It protects the team from spending art time on a layout that does not yet work.
Key ideas
- Playable scale first. Doorways, corridors, platforms, cover and jumps must fit the player controller before art detail matters.
- Route clarity. The player should understand where they can go and what the next goal is.
- Camera checks. A space that looks clear in Scene view can fail in the game camera.
- Collision checks. Floors, walls, stairs and ramps should be tested with the real player object as soon as possible.
- Cheap iteration. Move cubes and ProBuilder shapes while the design is still flexible.
- Intentional labels. Temporary colours can mark safe path, danger, goal, locked door, reward and player start.
In practice
Basic Unity workflow
- Choose a simple scene goal, such as collect three objects and reach an exit.
- Create a floor, walls and main route from cubes or ProBuilder shapes.
- Turn on grid snapping so dimensions stay regular.
- Add a player-sized reference object, such as a capsule.
- Place a camera and test from the game view.
- Add temporary materials for route, danger, reward and blocked paths.
- Add simple colliders and run through the scene in Play mode.
- Move, resize or delete shapes until the space works.
- Only then replace key shapes with imported props or final art.
Unity’s ProBuilder material supports this workflow directly. Unity Learn teaches basic shapes, snapping, pivots, real-size checks and a level-design challenge as early ProBuilder tasks (Unity Technologies, Build Basic Shapes, see source-unity-probuilder-greyboxing). The package documentation also describes the Shape Tool as a way to create new ProBuilder meshes from common primitives such as cubes, cylinders, arches and stairs (Unity Technologies, ProBuilder Shape Tool, see source-unity-probuilder-greyboxing).
What to measure
| Area | Beginner check |
|---|---|
| Door height | player passes through without camera clipping |
| Corridor width | player can turn without snagging |
| Stair height | player controller can climb or step smoothly |
| Platform gap | jump or movement ability matches the intended challenge |
| Cover size | player can understand what blocks sight or bullets |
| Goal visibility | goal appears in the game camera within the intended time |
What to leave rough
Do not model final props, decoration, bevels, decals, complex textures or polished lighting during the first blockout. Use temporary labels and materials instead. The greybox should make the design legible enough to test, not pretty enough to ship.
Evidence
Villar’s 3D pipeline argues that preproduction is the stage where project purpose, design and planning are worked out before production becomes expensive (Villar, Learning Blender, see source-learning-blender). Greyboxing applies that same principle to a playable Unity space.
Unity’s ProBuilder Shape Tool documentation emphasises primitive shape creation, bounding-box sizing, pivot choice and snapping support (Unity Technologies, ProBuilder Shape Tool, see source-unity-probuilder-greyboxing). These are exactly the controls beginners need when learning to build at a deliberate scale.
Implications
- A blockout is a design argument. It says, “this route, scale and interaction will work.”
- Final art should answer the greybox, not fight it.
- Lighting and materials can guide players during greybox tests, but should stay simple enough to change quickly.
- A failed greybox is a useful result because it catches a spatial problem before the asset pipeline becomes expensive.
Practice
Build a one-room greybox:
- Add a start point, goal, raised platform and blocked door.
- Use only cubes, ProBuilder shapes and temporary materials.
- Add one clear route and one optional side route.
- Test in Play mode from the game camera.
- Ask another student to play for one minute without explanation.
- Record three observations: where they looked first, where they hesitated, and where they collided with the space.
Self-test
- What is the main purpose of a greybox?
- Why should greyboxing happen before final art?
- Why is the game camera a better test than Scene view?
- What do grid snapping and dimensions help prevent?
- Which one should be fixed first: a beautiful prop or a doorway the player cannot pass through?
Answers
- The main purpose is to prove scale, movement, route, camera and interaction quickly.
- It is cheaper to move simple shapes than to rebuild final models, textures and lighting.
- The player sees the game camera, so readability must be judged from that view.
- They help prevent inconsistent scale, uneven spacing and accidental layout drift.
- The doorway should be fixed first because playability is blocking the whole space.