Webots World Building

Build and modify .wbt worlds by composing scene tree nodes, assigning geometry and materials, configuring lighting, and setting physically efficient collision and dynamics properties. Follow VRML97-derived syntax and ENU coordinates (X=East, Y=North, Z=Up, Webots R2022a+).

Do not include controller programming or API usage. Do not define new PROTO files in this skill.

When To Use

Use this skill for:

• Creating or restructuring scene trees
• Adding Solid objects and collision geometry
• Building terrain, arenas, and environment props
• Applying PBRAppearance, textures, and lighting
• Importing external meshes/CAD assets into a world

Core Workflow

1. Open world and identify target insertion point in the scene tree.
2. Add structural node (Group, Transform, Pose, Solid, or Robot) based on whether physical behavior is required.
3. Add visual geometry under Shape (geometry + appearance).
4. Add boundingObject using simple primitives for collisions.
5. Add Physics only when dynamic simulation is required.
6. Configure lighting/background for readability and realism.
7. Validate transforms, scale, and collision performance.

Scene Tree And Node Hierarchy

Choose the right container

• Group: collect children without transform or physics semantics.
• Transform: apply translation/rotation/scale to child nodes.
• Pose: apply transform with concise pose-centric semantics.
• Solid: represent a physical object in the world.
• Robot: use robot root when modeling articulated robots (without defining PROTO here).

Use Solid for anything that should collide, receive mass, or participate in dynamics. Keep purely decorative geometry under non-physical containers when possible.

Solid essentials

For Solid, manage three distinct concerns:

• children: visual geometry and subparts
• boundingObject: collision representation
• physics: inertial and damping behavior

Solid {
  translation 0 0 0.4
  children [
    Shape {
      appearance PBRAppearance {
        baseColor 0.7 0.7 0.7
        roughness 0.6
        metalness 0.1
      }
      geometry Box { size 0.4 0.4 0.8 }
    }
  ]
  boundingObject Box { size 0.4 0.4 0.8 }
  physics Physics { density -1 mass 12 }
}

Reuse nodes with DEF/USE

Define once, reuse many times for consistent materials, geometry, or transforms.

DEF GRAY_WALL_MAT PBRAppearance {
  baseColor 0.78 0.78 0.8
  roughness 0.85
  metalness 0
}

Shape {
  appearance USE GRAY_WALL_MAT
  geometry Box { size 4 0.1 1.2 }
}

Add nodes through the scene tree UI

In the scene tree, select parent node, press Add, then insert node type (Solid, Shape, PBRAppearance, DirectionalLight, etc.). Prefer this path for iterative world editing and immediate visual feedback.

Geometry Nodes

Use primitive geometry whenever possible for speed and stable collisions.

Primitive geometry examples

# Box
Shape {
  appearance PBRAppearance { baseColor 0.8 0.2 0.2 roughness 0.5 metalness 0 }
  geometry Box { size 1.0 0.6 0.4 }
}

# Sphere
Shape {
  appearance PBRAppearance { baseColor 0.2 0.4 0.9 roughness 0.3 metalness 0.2 }
  geometry Sphere { radius 0.2 }
}

# Cylinder
Shape {
  appearance PBRAppearance { baseColor 0.7 0.7 0.7 roughness 0.4 metalness 0.6 }
  geometry Cylinder { radius 0.1 height 0.5 }
}

# Capsule
Shape {
  appearance PBRAppearance { baseColor 0.3 0.9 0.5 roughness 0.6 metalness 0 }
  geometry Capsule { radius 0.08 height 0.4 }
}

# Cone
Shape {
  appearance PBRAppearance { baseColor 0.95 0.7 0.2 roughness 0.7 metalness 0 }
  geometry Cone { bottomRadius 0.15 height 0.4 }
}

# Plane (useful for floors)
Shape {
  appearance PBRAppearance { baseColor 0.5 0.5 0.5 roughness 0.95 metalness 0 }
  geometry Plane { size 6 6 }
}

Terrain with ElevationGrid

Shape {
  appearance PBRAppearance {
    baseColorMap ImageTexture { url ["textures/soil_diffuse.jpg"] }
    roughness 1
    metalness 0
  }
  geometry ElevationGrid {
    xDimension 5
    yDimension 5
    xSpacing 1.0
    ySpacing 1.0
    height [
      0.00, 0.05, 0.10, 0.05, 0.00,
      0.02, 0.10, 0.18, 0.10, 0.02,
      0.04, 0.15, 0.30, 0.15, 0.04,
      0.02, 0.10, 0.18, 0.10, 0.02,
      0.00, 0.05, 0.10, 0.05, 0.00
    ]
  }
}

Use height arrays as procedural heightmaps. Keep grid resolution moderate for real-time performance.

Custom mesh with IndexedFaceSet

Shape {
  appearance PBRAppearance { baseColor 0.6 0.6 0.65 roughness 0.7 metalness 0.1 }
  geometry IndexedFaceSet {
    coord Coordinate {
      point [
        0 0 0, 1 0 0, 1 1 0, 0 1 0,
        0 0 1, 1 0 1, 1 1 1, 0 1 1
      ]
    }
    coordIndex [
      0, 1, 2, 3, -1,
      4, 5, 6, 7, -1,
      0, 1, 5, 4, -1,
      1, 2, 6, 5, -1,
      2, 3, 7, 6, -1,
      3, 0, 4, 7, -1
    ]
    creaseAngle 0.7
  }
}

Import external assets with Mesh and CadShape

# Mesh import (.obj, .stl, .dae, .fbx)
Shape {
  appearance PBRAppearance { baseColor 1 1 1 roughness 0.6 metalness 0 }
  geometry Mesh { url ["models/chair.obj"] }
}

# CAD import through CadShape
CadShape {
  url ["models/fixture.step"]
}

For imported visuals, pair with simplified primitive boundingObject instead of mesh collisions when possible.

Appearance And Materials

Legacy Appearance + Material

Use when backward compatibility with older assets is required.

Shape {
  appearance Appearance {
    material Material {
      diffuseColor 0.8 0.2 0.2
      specularColor 0.2 0.2 0.2
      shininess 0.4
    }
  }
  geometry Box { size 0.4 0.4 0.4 }
}

Preferred PBRAppearance

Use physically based materials for modern rendering quality.

PBRAppearance {
  baseColor 0.7 0.7 0.7
  roughness 0.5
  metalness 0.2
  normalMap ImageTexture { url ["textures/metal_normal.png"] }
  occlusionMap ImageTexture { url ["textures/metal_ao.png"] }
}

Texture mapping and UV control

Shape {
  appearance PBRAppearance {
    baseColorMap ImageTexture { url ["textures/tiles_albedo.jpg"] }
    roughnessMap ImageTexture { url ["textures/tiles_roughness.jpg"] }
    normalMap ImageTexture { url ["textures/tiles_normal.jpg"] }
    textureTransform TextureTransform {
      scale 4 4
      rotation 0
      translation 0 0
    }
    roughness 1
    metalness 0
  }
  geometry Plane { size 8 8 }
}

Example: realistic wooden table

Solid {
  translation 0 0 0.38
  children [
    # Table top
    Shape {
      appearance PBRAppearance {
        baseColorMap ImageTexture { url ["textures/wood_albedo.jpg"] }
        roughnessMap ImageTexture { url ["textures/wood_roughness.jpg"] }
        normalMap ImageTexture { url ["textures/wood_normal.jpg"] }
        occlusionMap ImageTexture { url ["textures/wood_ao.jpg"] }
        roughness 0.85
        metalness 0
      }
      geometry Box { size 1.2 0.7 0.04 }
    }
    # Legs
    DEF TABLE_LEG Shape {
      appearance PBRAppearance {
        baseColorMap ImageTexture { url ["textures/wood_albedo.jpg"] }
        roughness 0.9
        metalness 0
      }
      geometry Box { size 0.06 0.06 0.72 }
    }
    Pose { translation 0.55 0.30 -0.38 children [ USE TABLE_LEG ] }
    Pose { translation -0.55 0.30 -0.38 children [ USE TABLE_LEG ] }
    Pose { translation 0.55 -0.30 -0.38 children [ USE TABLE_LEG ] }
    Pose { translation -0.55 -0.30 -0.38 children [ USE TABLE_LEG ] }
  ]
  boundingObject Box { size 1.2 0.7 0.76 }
  physics Physics { density -1 mass 18 }
}

Lighting And Environment

Use layered lighting: environment/sun + local accent lights.

DirectionalLight {
  direction -0.5 -0.3 -1
  color 1 0.98 0.95
  intensity 1.0
  ambientIntensity 0.25
  castShadows TRUE
}

PointLight {
  location 0 0 2.6
  color 1 0.95 0.85
  intensity 0.6
  radius 8
  castShadows TRUE
}

SpotLight {
  location 1.5 0.0 2.2
  direction -1 0 -1
  beamWidth 0.5
  cutOffAngle 0.9
  intensity 0.8
  castShadows TRUE
}

Background {
  skyColor [0.58 0.73 0.95]
  luminosity 1.0
}

For HDR environment reflections, assign HDR textures in Background texture fields where available in the world setup.

Physics Setup

Add Physics to dynamic solids

Use explicit mass properties for stable behavior.

Solid {
  children [ Shape { geometry Box { size 0.4 0.3 0.2 } } ]
  boundingObject Box { size 0.4 0.3 0.2 }
  physics Physics {
    density -1
    mass 4.0
    centerOfMass [ 0 0 0 ]
    inertiaMatrix [
      0.05 0 0
      0 0.07 0
      0 0 0.09
    ]
    damping Damping {
      linear 0.01
      angular 0.02
    }
  }
}

boundingObject best practices

• Prefer primitive shapes (Box, Sphere, Capsule, Cylinder) for collisions.
• Keep collision meshes coarse and convex when possible.
• Decouple visual mesh from collision geometry to reduce contact solver cost.
• Align boundingObject origin with Solid local frame to avoid offset mistakes.

Contact properties in WorldInfo

Configure pairwise material behavior globally:

WorldInfo {
  basicTimeStep 16
  contactProperties [
    ContactProperties {
      material1 "rubber"
      material2 "concrete"
      coulombFriction [1.0 0.8]
      bounce 0.05
      bounceVelocity 0.01
      softERP 0.2
      softCFM 0.00001
    }
  ]
}

Practical World-Building Examples

Create a simple arena with walls

DEF FLOOR Solid {
  children [
    Shape {
      appearance PBRAppearance { baseColor 0.35 0.35 0.35 roughness 0.95 metalness 0 }
      geometry Box { size 8 8 0.1 }
    }
  ]
  boundingObject Box { size 8 8 0.1 }
  locked TRUE
}

DEF WALL_MAT PBRAppearance { baseColor 0.8 0.8 0.82 roughness 0.9 metalness 0 }

DEF WALL Solid {
  children [ Shape { appearance USE WALL_MAT geometry Box { size 8 0.2 1 } } ]
  boundingObject Box { size 8 0.2 1 }
  locked TRUE
}

Pose { translation 0 4 0.5 children [ USE WALL ] }
Pose { translation 0 -4 0.5 children [ USE WALL ] }
Pose {
  translation 4 0 0.5
  rotation 0 0 1 1.5708
  children [ USE WALL ]
}
Pose {
  translation -4 0 0.5
  rotation 0 0 1 1.5708
  children [ USE WALL ]
}

Add stock objects (example: WoodenBox PROTO instance)

Instantiate built-in/available PROTO objects in the scene tree as world content:

WoodenBox {
  translation 0.5 0.3 0.1
  size 0.4 0.3 0.2
}

Use object insertion from the Add button and tune transform/material fields in place.

Set up indoor and outdoor environments

• Indoor: lower ambient light, add local PointLight and SpotLight, use high-roughness materials, assign wall/floor textures.
• Outdoor: use stronger DirectionalLight, brighter sky/background, terrain via ElevationGrid, sparse local fill lights.

Import external models safely

1. Import visual mesh via Mesh or CadShape.
2. Normalize scale and orientation to ENU frame.
3. Wrap in Solid and add simple boundingObject.
4. Add Physics only when dynamic behavior is needed.

Reference File

Use references/world_building_reference.md for detailed field-level node reference, supported texture/model formats, and physics/contact configuration tables.