Surface Map

SurfaceMap inspector.

SurfaceMap links terrain textures and object tags to a SurfacePreset that defines surface properties (friction, effects, audio). Each map represents one surface type in your scene.

How It Works

GroundDetection checks each wheel against all SurfaceMap entries to determine which surface the wheel is on. When a match is found, that surface's SurfacePreset is applied to the wheel.

Detection Priority

  1. Object tags (highest priority) - Allows objects to override terrain textures
  2. Terrain texture indices - Based on terrain splatmap sampling
  3. Fallback surface - When no matches are found

This priority system lets tagged objects (roads, bridges, ramps) override terrain textures beneath them.

Properties

Name

Display name for organization and debugging. Does not affect functionality.

Surface Preset

The SurfacePreset defining all properties for this surface type:

  • FrictionPreset for wheel physics (grip, slip curves)
  • Rolling resistance multiplier
  • Particle effects (dust/smoke)
  • Skidmark appearance and intensity
  • Surface-specific audio clips and volumes

Multiple SurfaceMap entries can reference the same SurfacePreset (e.g., different dirt texture variations).

Tags

Unity tags identifying objects as this surface type. When a wheel contacts an object with any of these tags, this surface map matches.

Use cases:

  • Non-terrain surfaces (roads, bridges, ramps)
  • Objects that override terrain textures
  • Indoor environments

Tags must be created in Unity's Tag Manager before use.

Terrain Texture Indices

Terrain texture indices. Note that counting starts from 0.

Indices of terrain textures representing this surface type. Corresponds to texture order in terrain's Paint Texture settings.

Important:

  • Index 0 = first texture (top-left in Paint Texture panel)
  • Zero-based indexing (0, 1, 2, ...)
  • Must match exact texture order in terrain setup
  • Multiple indices can map to the same surface (e.g., dirt variations)

Adding a Surface Map

Example: Adding a gravel surface.

  1. Click + button to add a new SurfaceMap
  2. Set a descriptive name (e.g., "Gravel")
  3. Assign the gravel SurfacePreset
  4. Find gravel texture positions in terrain settings. If gravel is at positions 5 and 7, add those numbers to Terrain Texture Indices
  5. (Optional) Create a tag like GravelRoad in Tag Manager, assign it to gravel objects in the scene, and add it to Tags list