True2Track: How the Surface Fights Back in Project Motor Racing

November 18, 2025

True2Track is a tile-based surface evolution system that simulates how a track changes over time due to rain and tyre activity. It models fluid behaviour (water puddles, drainage, evaporation) and rubber dynamics (rubber deposition that increases grip, and rubber marbles that reduce grip).

True2Track also runs primarily on the GPU for higher performance and serves as a single authoritative source of “truth” for other subsystems such as physics, AI, and rendering.

Deep Dive

What True2Track is responsible for

• Maintaining high-resolution track-surface state.
• Simulating water movement, puddle formation, and drying.
• Applying tyre-driven effects such as: rubber deposition, water removal (wiping), and marble generation/distribution.
• Supplying friction/grip and surface-condition data to physics and AI.
• Providing visualization output for rendering.

How the world is laid out: Tiles & Samples

True2Track partitions the world into regular square tiles with each tile covering roughly 10m².

Every tile is subdivided into many samples, with each sample covering about 7cm².

Each sample stores:

• Dynamic state: water depth, rubber amount, marbles amount.
• Static state: material parameters that describe how the sample responds to water and rubber (e.g., flow conductance, drainage speed, evaporation rate).

Water simulation: the pipe model

True2Track uses a pipe-network model to simulate water movement between neighbouring samples.

Core concept:

• Each sample is a node with a current water height/depth.
• Adjacent samples are connected by virtual “pipes”.
• Flow occurs based on height differences and per-sample conductance.
• The model runs in discrete timesteps and updates water exchange between neighbours.

Resulting behaviour:

• Puddles form naturally where geometry or material properties trap water.
• Water spreads across neighbours; deeper pools equilibrate via flows.
• When rain stops, evaporation and drainage gradually remove water and shrink puddles.

Tyres at work: rubber in, water out

When a tyre contacts the track, telemetry supplies per-tyre data (position, slip, contact patch area, tyre wear, speed, etc.).

True2Track consumes this data and applies local updates to the samples under the tyre contact.

Primary effects:

• Rubber deposition—increases grip along the racing line.
• Water removal—a tyre moving across a wet surface wipes a fraction of the water from contacted samples.

Marbles: generated, flung, and felt

Marbles are small chunks of rubber torn away from tyres and deposited off the racing line.

Generation:

• Marbles are driven by telemetry: slip events, lateral forces, tyre wear, and sudden transitions (e.g., lockups).
• Each marble event includes a spawn position (contact point) and emission direction derived from tyre velocity and lateral forces.

Trajectory & deposition:

• Marbles are deposited along a trajectory determined by emission direction and velocity.
• Samples where marbles land accumulate marbles amount value.
• Tyres impacting a marble-covered area remove some marbles as they adhere to the tyre.

Effect on grip:

• Marble accumulation reduces local grip (loose rubber on top of the track).
• Physics reads marbles’ amount to reduce friction when a car drives over them.

How True2Track powers the rest of the sim

True2Track acts as the authoritative source for surface-condition data.

Physics:

• Queries local water depth, rubber, and marbles.
• Uses this data to compute tyre forces, slip, hydroplaning thresholds, and braking distances.

AI:

• Uses surface-condition maps to choose racing lines.
• Prefers dry or rubberized lines over wet ones.
• Avoids areas with marbles or deep water where grip is poor.

Rendering & FX:

• Visual systems query True2Track to render puddles and modify surface materials with water and rubber.
• Data also drives dynamic spray particle effects.

The Result

With True2Track, the water flows, the line rubbers in, marbles accumulate, and the grip map evolves lap-by-lap—informing what you feel through physics, how AI chooses lines, and what you see on screen.

In short: one system, one truth, a living track.

Discuss this news item in our forum or in Discord.