Designed as a circuit racing simulator, Assetto Corsa lacked true gravel physics, relying on a simple model to simulate a loss of traction when going off-road. Fortunately from CSP v0.2.3 preview211 “SurfacesFX” was introduced to bring dedicated loose surface physics to Assetto Corsa! This page will keep track of what is known.

Development & availability

  • Still in early development phase as of June 2024
  • Currently reserved for preview (Patreon) versions but announced to be included in public builds in the near future
  • To enable SurfacesFX:
    • Enable “Active” under Settings > Custom Shaders Patch > SurfacesFX
    • Enable “Use extended physics” in Drive menu
  • Only available in offline races, or on servers that explicitly enable the option

Gravel tyres

  • 2 gravel test cars were provided in the Patreon post announcing CSP v0.2.4 preview1:
    • Rally version of the Kunos Toyota Celica, with the new default CSP gravel tyre
    • Toyota Yaris Rally1, with a more agressive/modern gravel tyre
  • Car mods need one of the above new tyres to work correctly with SurfacesFX – old mods with tweaked tarmac tyres won’t work as well
  • For CSP to recognize the new gravel tyres, tyres.ini should contain
    • TYPE_HINT=GRAVEL (the default CSP gravel tyre as on the Celica)
    • TYPE_HINT_MODIFIER=RALLY1 (optional, for the tyre as on the Yaris)
  • Online documentation

Track configuration

  • SurfacesFX alters physics not only on gravel but also on grass and sand.
  • Most tracks should work out of the box, but to be sure simply open “data/surfaces.ini” and add “_EXT_SURFACE_TYPE=GRAVEL” to sections with gravel.
  • Loose surface type can be tweaked using “_EXT_SURFACE_TYPE_MODIFIER” = LOOSE, REGULAR (=default) or FIRM
  • If surface type is not explicitly set to gravel, SurfacesFX will automagically activate for surfaces with 
    • DIRT_ADDITIVE ≥ 0.7
    • surfaces with DIRT_ADDITIVE ≥ 0.3 and FRICTION < 0.9
    • WAV set to “grass.wav”, “gravel.wav” or “sand.wav”
  • Some tracks may have issues with SurfacesFX – for now the only option is to disable it in CSP settings
  • Friction >= 0.9 may still cause tyre squeal
  • GrassFX on the road surface will inhibit dust clouds behind the car
  • Online documentation and some interesting observations in AssettoCorsaMods forum

Reference surface

As provided by CSP devs: