This manual explains how TORCS tracks are authored and processed. It starts with an easy conceptual view and then goes into reference-level detail. It focuses on TORCS behavior and data formats, and discusses AC3D/Blender only where needed for alignment-safe post-editing. It covers the most recent TORCS track XML format, version 4 (v4). The TORCS track editor is not discussed here.

Contents

1. XML and 3D model
2. Authoring workflow overview
3. Tool workflow in detail (trackgen, accc)
4. Top-level XML structure
5. Main Track defaults
6. Segment geometry (str, lft, rgt)
7. Elevation and banking
8. Profile modes (linear vs spline)
9. Interpolation and sub-segmentation
10. Side, border, barrier and variable width
11. Guidance: when to use side, border, or both
12. Surface system deep dive (physics + rendering)
13. Terrain generation chapter (Graphic/Terrain Generation)
14. trackgen -E elevation export modes
15. Pits and cameras
16. Units and numeric interpretation
17. Advanced fields and compatibility notes
18. Reference tables
19. Author checklist

1. XML and 3D model

When you create a TORCS track, there are two related descriptions:

Logical/physical description (XML)
- segment layout, elevations, banking, side areas
- surfaces and physical coefficients
- pits, cameras, terrain generation settings
Visual model (.ac)
- rendered geometry used by graphics
- referenced from Graphic/3d description (usually <name>.ac or <name>.acc)

Think of it as:

XML = how the track behaves
.ac or .acc = how the track looks

Both should stay consistent. If they drift apart, players can see one edge and collide with another.

2. Authoring workflow overview

For command-line helpers that convert maps or drawings into track layouts and add curbs, pits, and elevation, see the Track Tools Guide.

Typical loop:

Edit name.xml.
Generate assets with trackgen.
Optionally post-process with accc.
Test in TORCS.
Iterate back to 1.
Optional: Generate raceline geometry with trackgen -r.
Optional: Edit/add objects in a 3D modeling tool such as AC3D or Blender.
Optional: Combine raceline, shading, and track AC files with accc into the final track model.

For beginners: start with simple geometry and defaults, then add complexity in this order:

segments and width
elevation and banking
side/border/barrier tuning
surfaces and textures
pits/cameras
terrain and tool-specific refinements

For a compact applied snippet that combines these concepts, see 11.1 Mini end-to-end XML example.

2.1 License and assets (boring, but important)

Track metadata and asset rights should be explicit from the beginning. Beware, if you are not clear about it or choose incompatible licensing with TORCS, your track cannot be integrated in TORCS or further developed by other people later:

set author and description in XML Header
add a clear license statement in track README
document third-party asset source, author, and license

Do not use random internet assets with unknown license state. Do not include commercial/proprietary assets unless redistribution and derivative-use rights are explicitly compatible with your track release.

If you reuse TORCS assets, your track is a derivative work of TORCS content and must be distributed under terms compatible with TORCS licensing (GPL version 2 or later).

Practical recommendation for README:

License section for XML/AC/ACC/textures
Authors and attribution list
Third-party assets table (source URL, license, modifications)
short note about whether redistribution and modification are allowed

2.2 Track categories and paths

Tracks are stored in tracks/<category>/<name>/, with their definition named <name>.xml. Set Header/category to the same category ID used in the directory and in trackgen -c <category> -n <name>.

Category ID	Display name	Purpose
`road`	Road Tracks	Established road racing circuits.
`oval`	Oval Tracks	Oval racing circuits.
`dirt`	Dirt Tracks	Dirt and mixed-surface racing circuits.
`experimental`	Experimental Tracks	Playable work-in-progress tracks.
`test`	Test Tracks	Technical layouts for testing geometry, rendering, physics, and tooling.

For example, an experimental track belongs at tracks/experimental/mytrack/mytrack.xml and uses <attstr name="category" val="experimental"/> in its Header.

Category display names come from data/tracks/<category>.xml. The track selector discovers categories dynamically and skips those without valid track definitions.

3. Tool workflow in detail (trackgen, accc)

trackgen basics

Trackgen takes the track XML file as input and generates the initial 3D-model or model parts (.ac files). Basic command:

trackgen -c <category> -n <name>

Common options:

-c, -n: category and track name (required).
-a: generate all (track + terrain path).
-s: split track and terrain output.
-S: split all output.
-b: bump-track generation mode.
-r: raceline-track generation mode.
-z: calculate and exit (no full generation).
-B: do not auto-generate border from rectangle; use relief border.
-E <n>: export elevation image mode (detailed in chapter 14).
-H <nb>: height step count for -E 4.
-i <xml_path>, -o <ac_path>: useful for tests/custom paths.

Example:

trackgen -c road -n mytrack -a

accc basics

accc transforms or merges AC3D files.

Track-focused use cases:

+shad: generate a shading-oriented AC3D file.
-g ... -l0 ... -l1 ...: combine multilayer geometry.
+o: optimize track-zone grouping output.

Car-oriented options (+s, +es, +et) are available but are not the primary path for basic track authoring.

Example track merge flow:

accc +shad name-bak.ac name-shade.ac

accc -g name.ac -l0 name-bak.ac -l1 name-shade.ac -d3 1000 -d2 500 -d1 300 -S 300 -es

3.1 3D model alignment contract (AC3D/Blender edits)

This is the critical rule when editing generated .ac files:

physics/collision use the XML-generated track geometry
graphics render Graphic/3d description
they only line up because both use the same coordinates

If you move/rotate/scale the generated road mesh in AC3D/Blender, visuals and physics drift apart.

What exactly is (0,0,0)

TORCS computes a bounding box from generated track geometry (track only, without terrain/scenery), then shifts all segment and camera coordinates so the minimum corner becomes (0,0,0).

It is the corner with minimum x, minimum y, minimum z.
It is not tied to the start line.
It is based on generated track geometry (main/side/border vertices), not terrain.
Barrier thickness does not expand this origin box because barrier width is stored as barrier metadata, not as extra boundary vertices.

Geographic metadata uses a different reference: the road centre at the start of the first segment. See 4.1 Optional georeference.

In practice this means: if you inspect the model, origin often appears aligned with the inner side of wall barriers (before barrier thickness), which is expected.

Is origin location random from the start grid perspective?

No. With standard generation and start direction, origin is deterministic:

it is at or behind start in x
it is at or right of start in y

So origin is in the back-right quadrant (including boundaries) when you face race direction on the grid.

AC3D axis mapping to TORCS

When loading AC3D vertices, TORCS remaps axes as:

x_torcs = x_ac3d
y_torcs = -z_ac3d
z_torcs = y_ac3d

So AC3D up-axis (Y) becomes TORCS up-axis (Z), and AC3D Z maps to TORCS Y with sign inversion.

Safe and unsafe post-edits

Safe edits:

add scenery objects
tweak materials/textures/UVs
merge layers with accc while keeping base road geometry unchanged

Unsafe edits:

global transform (move/rotate/scale) of generated road mesh
editing road chunk coordinates without regenerating from XML
deleting/renaming structural track chunks used by grouping workflows

Quick validation after edits:

trackgen closure deltas remain near zero
visible road edge matches drivable/collision edge in-game
pits and cameras still line up

4. Top-level XML structure

Typical layout (simplified):

<params name="..." type="trackdef" mode="mw">
  <section name="Header">
    <attnum name="version" val="4"/>
    <!-- name, category, author, description -->
  </section>
  <section name="Georeference"> ... </section> <!-- optional -->
  <section name="Surfaces"> ... </section>
  <section name="Graphic"> ... </section>
  <section name="Main Track">
    <section name="Left Side"> ... </section>
    <section name="Right Side"> ... </section>
    <section name="Left Border"> ... </section>
    <section name="Right Border"> ... </section>
    <section name="Left Barrier"> ... </section>
    <section name="Right Barrier"> ... </section>
    <section name="Pits"> ... </section>
    <section name="Track Segments"> ... </section>
  </section>
  <section name="Cameras"> ... </section>
</params>

Use exact key strings from track.h.

4.1 Optional georeference

Version-4 tracks can contain an optional top-level Georeference section. Its values refer to the main-road centre at the beginning of the first segment, the simulated start/finish line.

<section name="Georeference">
  <attnum name="latitude" unit="deg" val="45.1234567"/>
  <attnum name="longitude" unit="deg" val="7.1234567"/>
  <attnum name="altitude" unit="m" val="230.5"/>
  <attnum name="heading" unit="deg" val="90"/>
</section>

Key	Meaning
`latitude`	WGS84 latitude in degrees, north positive; between -90 and 90.
`longitude`	WGS84 longitude in degrees, east positive; between -180 and 180.
`altitude`	Metres above approximate mean sea level at the road centre. Zero and negative values are valid.
`heading`	Driving direction in degrees clockwise from true north: 0 north, 90 east, 180 south, 270 west.

Omit unknown values; latitude and longitude must be supplied together. The whole section may be omitted, for example for a fantasy circuit. Altitude here is independent of the terrain generation altitude range.

These values are currently informational and do not affect track geometry or racing, but might be used in the future to place the track on a world map or retrieve local weather.

5. Main Track defaults

Main Track provides default values used by segments:

width
surface
profil steps length
default side/border/barrier sections

Important behavior:

Main segment width is effectively global (Main Track/width used for runtime main segments).
If you need local widening/narrowing, use side/border design, not per-main-segment road width.

6. Segment geometry (str, lft, rgt)

Each Main Track/Track Segments/<segment> entry is one authoring segment. Segments are listed in driving order. Left and right are viewed facing the direction of travel.

type="str": straight; lg specifies its length.
type="lft": left-hand turn; requires radius and arc (turn angle).
type="rgt": right-hand turn; requires radius and arc.
end radius optional: enables varying-radius turns.

Example:

<section name="curve 1">
  <attstr name="type" val="rgt"/>
  <attnum name="arc" unit="deg" val="40.0"/>
  <attnum name="radius" unit="m" val="160.0"/>
  <attnum name="end radius" unit="m" val="100.0"/>
</section>

7. Elevation and banking

Plain language:

z ... values define height.
grade defines longitudinal slope; positive values climb in driving direction.
banking ... defines left-right tilt; positive angles raise the left edge relative to the right.

Loader resolution order (important):

continuity from previous segment
explicit start values (z start overrides side-specific start)
end centre height (z end, else grade, else the average of side-specific end heights)
banking effects (banking start/end) applied where specified

Practical advice:

Prefer one clear method per segment.
If you combine methods, do so intentionally and test seams.

8. Profile modes (linear vs spline)

profil (the literal XML spelling for "profile") controls how vertical profile changes inside a segment.

linear: constant slope across the segment.
spline: smooth curve from start to end heights.

What is a spline here?

The loader uses Hermite interpolation (TrackSpline): start and end heights plus tangent values shape the curve.

Tangent fields:

profil start tangent, profil end tangent
profil start tangent left/right, profil end tangent left/right

Generic tangents override side-specific tangents at the same boundary.

9. Interpolation and sub-segmentation

Key model:

XML segment = authoring unit
runtime segment(s) = simulation/render units

One authored segment may become multiple runtime segments.

Step count logic

For profil="spline":

start with profil steps
if profil steps == 1: steps = int(length / profil steps length) + 1
if segment-local profil steps length missing: fallback to Main Track/profil steps length

For profil="linear": steps = 1 in loader behavior.

What is interpolated per runtime segment

vertical profile
side width (start width -> end width)
attached side/border/barrier geometry

Example:

lg = 180m, profil="spline", profil steps length = 15m
steps = int(180/15)+1 = 13

10. Side, border, barrier and variable width

Outward from main track on each side:

border
side
barrier

Variable-width behavior:

side supports continuous taper (start width, end width)
border width is effectively constant within one authored segment
border can change on each segment

banking type for sides:

level: level across the side's width, starting at the adjoining edge height.
tangent: continues the adjoining road's cross-slope across the side.

10.1 Curb height behavior (style="curb")

height on curb-style border segments is not just decorative. It affects both sampled track height and generated geometry.

Runtime height sampling behavior (RtTrackHeightL()):

base height is first computed from segment z-profile and banking
curb then adds a cross-width offset that ramps linearly across the curb width
formula conceptually is:
- base_height + alpha * (curb_height + curb_roughness) / width
alpha runs across the curb width and is mirrored for right-border orientation
curb_roughness comes from surface roughness and wavelength along segment length

Practical effect:

wheel/body height on curbs rises smoothly from one edge to the other
curb can carry extra ripple from the assigned surface roughness model

10.2 Wall behavior and collision model (style="wall")

There are two relevant collision paths:

Barrier-line collision (always active when crossing barrier bounds)
- car corner outside left/right bounds collides against segment barrier normal
- response uses barrier surface properties (friction, rebound, dammage)
Solid wall object collision (style-driven)
- collision solids are built from contiguous TR_WALL chains
- wall height is used to extrude vertical polygons
- this path is explicitly wall-style specific

Important limitation from current simulation code:

dedicated solid collision generation exists for wall-style chains
curbs and flat plan borders are not handled as full solid wall objects in that path

Authoring implication:

if you need strong body-blocking vertical behavior, use style="wall" with meaningful height
if you need drivable edge elevation behavior, use style="curb" and tune height

11. Guidance: when to use side, border, or both

Use border only when:

you need a narrow fixed edge (curb/paint/lip)

Use side only when:

you need runoff/apron with taper

Use both when:

you want realistic layering: asphalt -> curb(border) -> runoff(side) -> barrier

Pit merge rule of thumb:

taper side across multiple segments
keep border minimal in crossing zones

11.1 Mini end-to-end XML example

This is a full runnable example designed for copy/paste, just try it. It uses an oval layout (two 180-degree turns), a realistic pit lane layout with 20 pit slots, and demonstrates banking plus a descending counter-straight.

<?xml version="1.0" encoding="UTF-8"?>
<!-- 
    file                 : manual_oval.xml
    copyright            : (C) 2026 by Bernhard Wymann
-->
<!--    This program is free software; you can redistribute it and/or modify  -->
<!--    it under the terms of the GNU General Public License as published by  -->
<!--    the Free Software Foundation; either version 2 of the License, or     -->
<!--    (at your option) any later version.                                   -->
 
<!DOCTYPE params SYSTEM "../../../src/libs/tgf/params.dtd" [
<!ENTITY default-surfaces SYSTEM "../../../data/tracks/surfaces.xml">
<!ENTITY default-objects SYSTEM "../../../data/tracks/objects.xml">
]>
<params name="Manual Oval" type="trackdef" mode="mw">
  <section name="Header">
    <attstr name="name" val="Manual Oval"/>
    <attstr name="category" val="road"/>
    <attnum name="version" val="4"/>
    <attstr name="author" val="Track Manual"/>
    <attstr name="description" val="Runnable example with pits"/>
  </section>
 
  <section name="Graphic">
    <attstr name="3d description" val="manual_oval.ac"/>
    <attstr name="background image" val="background.png"/>
    <attnum name="background type" val="4"/>
    <section name="Environment Mapping">
      <section name="1">
        <attstr name="env map image" val="env.png"/>
      </section>
    </section>
    <section name="Terrain Generation">
      <attnum name="track step" unit="m" val="8"/>
      <attnum name="border margin" unit="m" val="140"/>
      <attnum name="border step" unit="m" val="16"/>
      <attnum name="terrain transition" unit="m" val="140"/>
      <attnum name="border height" unit="m" val="0"/>
      <attstr name="surface" val="gravel"/>
    </section>
  </section>
 
  <section name="Surfaces">
    &default-surfaces;
 
    <!-- Custom main-road surface with raceline overlay texture -->
    <section name="manual-asphalt">
      <attstr name="texture name" val="tr-road1.rgb"/>
      <attstr name="texture type" val="continuous"/>
      <attnum name="texture size" unit="m" val="15.0001"/>
      <attnum name="texture mipmap" unit="m" val="0.0"/>
      <attstr name="texture start on boundary" val="yes"/>
      <attstr name="texture link with previous" val="yes"/>
      <attstr name="raceline name" val="raceline.png"/>
      <attnum name="friction" val="1.06"/>
      <attnum name="rolling resistance" val="0.021"/>
      <attnum name="roughness" val="0.0007"/>
      <attnum name="roughness wavelength" val="2.0"/>
    </section>
  
    <section name="manual-barrier">
      <attstr name="texture name" val="arbor2_n.rgb"/>
      <attstr name="texture type" val="continuous"/>
      <attnum name="texture size" val="10.0" unit="m"/>
      <attnum name="texture mipmap" val="0.0"/>
      <attnum name="friction" val="0.0"/>
      <attnum name="dammage" val="10"/>
    </section>
  </section>
 
  <section name="Main Track">
    <attnum name="width" unit="m" val="12.0"/>
    <attstr name="surface" val="manual-asphalt"/>
    <attnum name="profil steps length" unit="m" val="4.0"/>
    <attnum name="raceline widthscale" val="1.5"/>
    <attnum name="raceline int" val="3"/>
    <attnum name="raceline ext" val="3"/>
 
    <section name="Left Border">
      <attnum name="width" unit="m" val="0.8"/>
      <attnum name="height" unit="m" val="0.04"/>
      <attstr name="style" val="curb"/>
      <attstr name="surface" val="curb-5cm-l"/>
    </section>
    <section name="Right Border">
      <attnum name="width" unit="m" val="0.8"/>
      <attnum name="height" unit="m" val="0.04"/>
      <attstr name="style" val="curb"/>
      <attstr name="surface" val="curb-5cm-r"/>
    </section>
 
    <section name="Left Side">
      <attnum name="width" unit="m" val="5.0"/>
      <attstr name="banking type" val="tangent"/>
      <attstr name="surface" val="grass6"/>
    </section>
    <section name="Right Side">
      <attnum name="width" unit="m" val="4.0"/>
      <attstr name="banking type" val="level"/>
      <attstr name="surface" val="grass6"/>
    </section>
 
    <section name="Left Barrier">
      <attnum name="width" unit="m" val="0.0"/>
      <attnum name="height" unit="m" val="4.0"/>
      <attstr name="style" val="fence"/>
      <attstr name="surface" val="manual-barrier"/>
    </section>
    <section name="Right Barrier">
      <attnum name="width" unit="m" val="0.5"/>
      <attnum name="height" unit="m" val="1.2"/>
      <attstr name="style" val="wall"/>
      <attstr name="surface" val="wall"/>
    </section>
 
    <section name="Pits">
      <attstr name="type" val="track side"/>
      <attstr name="side" val="right"/>
      <attstr name="entry" val="pit_entry"/>
      <attstr name="start" val="pit_main"/>
      <attstr name="end" val="pit_main"/>
      <attstr name="exit" val="pit_exit"/>
      <attnum name="speed limit" unit="km/h" val="80"/>
      <attnum name="length" unit="m" val="15"/>
      <attnum name="width" unit="m" val="5.0"/>
    </section>
 
    <section name="Track Segments">
      <section name="pit_entry">
        <attstr name="type" val="str"/>
        <attnum name="lg" unit="m" val="200.0"/>
        <section name="Right Side">
          <attstr name="surface" val="manual-asphalt"/>
          <attnum name="start width" unit="m" val="4.0"/>
          <attnum name="end width" unit="m" val="14.2"/>
        </section>
        <section name="Right Border">
          <attstr name="style" val="plan"/>
          <attstr name="surface" val="b-road1-l2p"/>
        </section>
      </section>
 
      <section name="pit_main">
        <attstr name="type" val="str"/>
        <attnum name="lg" unit="m" val="300.0"/>
        <section name="Right Side">
          <attstr name="surface" val="road1-pits"/>
          <attnum name="start width" unit="m" val="14.5"/>
          <attnum name="end width" unit="m" val="14.5"/>
        </section>
        <section name="Right Border">
          <attstr name="style" val="wall"/>
          <attstr name="surface" val="wall"/>
          <attnum name="width" unit="m" val="0.5"/>
          <attnum name="height" unit="m" val="1.0"/>
        </section>
        <section name="Left Border">
          <attnum name="width" unit="m" val="0.8"/>
          <attstr name="style" val="plan"/>
          <attstr name="surface" val="b-road1-grass6"/>
        </section>
      </section>
 
      <section name="pit_exit">
        <attstr name="type" val="str"/>
        <attnum name="lg" unit="m" val="200.0"/>
        <attnum name="banking start" unit="deg" val="0.0"/>
        <attnum name="banking end" unit="deg" val="15.0"/>
        <section name="Right Side">
          <attstr name="surface" val="manual-asphalt"/>
          <attnum name="start width" unit="m" val="14.2"/>
          <attnum name="end width" unit="m" val="4.0"/>
        </section>
        <section name="Right Border">
          <attstr name="style" val="plan"/>
          <attstr name="surface" val="b-road1-l2p"/>
          <attnum name="width" unit="m" val="0.8"/>
        </section>
      </section>
 
      <section name="turn_1">
        <attstr name="type" val="rgt"/>
        <attnum name="radius" unit="m" val="90.0"/>
        <attnum name="arc" unit="deg" val="180.0"/>
        <attnum name="z end" unit="m" val="-10.0"/>
        <attnum name="profil steps length" unit="m" val="3.0"/>
        <attnum name="banking start" unit="deg" val="15.0"/>
        <attnum name="banking end" unit="deg" val="15.0"/>
        <attstr name="marks" val="50;100"/>
        <section name="Right Border">
          <attstr name="style" val="curb"/>
          <attstr name="surface" val="curb-5cm-r"/>
          <attnum name="height" unit="m" val="0.06"/>
        </section>
        <section name="Right Side">
          <attstr name="surface" val="grass6"/>
          <attnum name="start width" unit="m" val="4.0"/>
          <attnum name="end width" unit="m" val="4.0"/>
        </section>
      </section>
 
      <section name="counter_straight_end_banking">
        <attstr name="type" val="str"/>
        <attnum name="lg" unit="m" val="200.0"/>
        <attnum name="banking start" unit="deg" val="15.0"/>
        <attnum name="banking end" unit="deg" val="0.0"/>
        <attnum name="z end" unit="m" val="5.0"/>
        <section name="Right Border">
          <attstr name="style" val="plan"/>
          <attstr name="surface" val="b-road1-grass6"/>
        </section>
      </section>
 
      <section name="counter_straight">
        <attstr name="type" val="str"/>
        <attnum name="lg" unit="m" val="300.0"/>
        <attnum name="z end" unit="m" val="0.0"/>
      </section>
 
      <section name="counter_straight_start_banking">
        <attstr name="type" val="str"/>
        <attnum name="lg" unit="m" val="200.0"/>
        <attnum name="z end" unit="m" val="0.0"/>
        <attnum name="banking start" unit="deg" val="0.0"/>
        <attnum name="banking end" unit="deg" val="12.0"/>
      </section>
 
      <section name="turn_2">
        <attstr name="type" val="rgt"/>
        <attnum name="radius" unit="m" val="90.0"/>
        <attnum name="arc" unit="deg" val="180.0"/>
        <attnum name="profil steps length" unit="m" val="3.0"/>
        <attstr name="marks" val="50;100"/>
        <attnum name="banking start" unit="deg" val="12.0"/>
        <attnum name="banking end" unit="deg" val="0.0"/>
        <section name="Right Border">
          <attstr name="style" val="curb"/>
          <attstr name="surface" val="curb-5cm-r"/>
          <attnum name="width" unit="m" val="0.8"/>
          <attnum name="height" unit="m" val="0.06"/>
        </section>
      </section>
    </section>
  </section>
</params>

Suggested file path:

tracks/road/manual_oval/manual_oval.xml

Generate with:

trackgen -c road -n manual_oval -a

Raceline workflow (easy-start variant using global data/textures/raceline.png):

# 1) Generate regular track and terrain output
trackgen -c road -n manual_oval -a
 
# 2) Generate raceline geometry layer
trackgen -c road -n manual_oval -r
 
# 3) Required for normal in-game use: combine into final ACC model
#    (same pattern as track readme files)
accc -g tracks/road/manual_oval/manual_oval.acc \
  -l0 tracks/road/manual_oval/manual_oval.ac \
  -l1 tracks/road/manual_oval/manual_oval-trk-raceline.ac \
  -d3 1000 -d2 500 -d1 300 -S 300 -es

If you also use a baked shadow layer, a common layout is:

accc -g tracks/road/manual_oval/manual_oval.acc \
  -l0 tracks/road/manual_oval/manual_oval.ac \
  -l1 tracks/road/manual_oval/manual_oval-shade.ac \
  -l2 tracks/road/manual_oval/manual_oval-trk-raceline.ac \
  -d3 1000 -d2 500 -d1 300 -S 300 -es

Raceline shaping keys in Main Track:

raceline widthscale: global width scaling for generated raceline strip.
raceline int: safety margin to inside border (meters).
raceline ext: safety margin to outside border (meters).

The example uses 1.5 / 3 / 3 (same style as g-track-1) for a clearly visible, conservative driving line.

Notes:

If accc fails with stripe: command not found, your environment is missing the external stripe tool used by this conversion path.
On Linux, install stripe from source/build tooling so ACC merge can complete.
Download links (archived original distribution):
- https://web.archive.org/web/20131004102243/http://www.cs.sunysb.edu/~stripe/stripe.tar.gz
- https://web.archive.org/web/20131004102245/http://www.cs.sunysb.edu/~stripe/stripe.zip
In the Windows binary installer stripe is already included.

To render the combined model in-game, change:

to:

What this demonstrates:

Full file structure (Header, Graphic, Surfaces, Main Track).
Closed-loop geometry with two 180-degree turns and long straights.
Default TORCS surface library via default-surfaces entity include.
Pit entry/exit on 200m straights with flat (plan) border sections.
Pit main section with wall border and 20 pit slots.
Banking on one turn and descending grade on counter straight.
marks as turn-marker distances on the turns.

11.2 State and fallback rules for omitted fields

The loader reads segments sequentially and keeps state for several fields. So omitted values are resolved by per-field fallback chains. It is not purely "always from Main Track" and not purely "always from previous segment".

Field	If omitted in current segment	Initial source
`surface` (main segment)	keeps previous segment surface	`Main Track/surface`
`Left/Right Side/start width`	defaults to previous side `end width`	`Main Track/Left\|Right Side/width`
`Left/Right Side/width`	defaults to segment `start width`	derived in segment
`Left/Right Side/end width`	defaults to segment `width`	derived in segment
side/border/barrier `surface`	keeps previous state	matching `Main Track` default subsection
side/border/barrier `style`	keeps previous state	matching `Main Track` default subsection
`profil steps length`	uses global value	`Main Track/profil steps length`
profile start tangents	continue from previous segment end tangents	`0` (if no prior data)
`z start left/right`	continues from previous segment end heights	`0` at beginning

Elevation precedence within a segment is separate from state carry-over:

z start overrides side-specific start heights
z end overrides side-specific end heights
if z end is absent and grade is present, end center height is derived from grade
if banking is present, left/right end heights are recomputed from center height and banking angles

Practical authoring rule:

segment order matters when fields are omitted
at transition points (pit entry/start/end/exit, first turn after pits), set key fields explicitly to avoid accidental state carry-over

12. Surface system deep dive (physics + rendering)

Surfaces are defined in Surfaces/<name>. Segments and side elements reference surface names via surface.

12.1 Physics properties

Read by track loader (track4.cpp) into tTrackSurface:

friction
rolling resistance
roughness
roughness wavelength
dammage
rebound

Defaults used if a field is absent are in loader code (getTrackSurface).

Meaning at high level:

friction: tire grip potential.
rolling resistance: baseline drag from surface contact.
roughness and roughness wavelength: small-scale vertical disturbance model.
dammage: collision damage factor for that material context (the double-m spelling is required in XML).
rebound: restitution-like response.

12.2 Rendering and texture properties

Used mainly by trackgen rendering export paths:

texture name
texture type (continuous vs discrete)
texture link with previous
texture start on boundary
texture size
texture size v (crossing mapping only; see section 13.4)
texture mipmap
bump name, bump size
raceline name
color fields (color R1/G1/B1, color R2/G2/B2)

Practical meaning:

texture size controls repetition scale.
texture link with previous=yes keeps texture continuity across segments.
texture start on boundary=yes aligns texture start with segment boundary.
bump and raceline textures are optional overlays for specific generation modes.

12.3 Surface authoring tips

Reuse a small, named library of surfaces (asphalt, curb, grass, gravel, wall).
Keep physics intent clear first, then tune texture look.
Avoid too many near-duplicate surfaces unless needed for visual variation.

12.4 Texture loading order, formats, and transparency quirks

Texture search order

For track model loading, graphics uses this search order:

tracks/<category>/<trackname>
data/textures
data/img
.

Background loading uses a very similar order but checks data/img before data/textures.

Practical implication:

if the same texture basename exists in multiple places, first match wins
prefer track-local textures for portable tracks, and avoid ambiguous duplicate names

Supported texture formats in this path

.png
.rgb

Mipmap behavior (important quirk)

The renderer applies filename heuristics:

textures ending with _n... disable mipmapping
textures containing shadow disable mipmapping

So texture mipmap in surface definitions is a hint, but these filename rules can still override mipmap behavior.

Transparency behavior (filename-triggered)

AC loading enables special alpha-test/blend handling when texture name contains:

tree
arbor
trans-

Additionally, material alpha from AC (mat->rgb[3]) is checked:

if alpha is below 0.99, geometry is treated as translucent (alpha-test/blend path)
if alpha is >= 0.99, it follows the opaque path unless filename-triggered rules apply

This is commonly used for vegetation and fence-card textures.

Why this convention exists:

alpha cutout textures with mipmaps can create mixed-alpha fringe/halo artifacts (often dark outlines at distance)
using cutout naming plus _n (no mipmaps) is a common TORCS pattern to reduce those artifacts

You can see this pattern in stock content (for example e-track-2 tree/arbor textures).

13. Terrain generation chapter (Graphic/Terrain Generation)

Key fields:

track step: sampling distance along the track boundary. It also provides the lower spacing limit propagated from densely sampled boundary points, capped by border step.
border margin: terrain extent around track bounds.
border step: coarse terrain-mesh target spacing away from the track.
terrain transition: distance from the track over which target spacing grows from the local track-boundary spacing to border step.
crossing bridge socket gap: lateral clearance outside each side of a lower track at an automatically detected grade-separated crossing; default 0.5 m.
crossing bridge thickness: minimum vertical thickness below the upper track surface at an automatically detected crossing; default 1.0 m.
border height: external border wall/height behavior.
group size: split size for terrain grouping (performance/scene graph).
surface: terrain base surface material.
relief file: optional AC3D relief constraints.
elevation map: grayscale height map input.
maximum altitude, minimum altitude: grayscale-to-height mapping range.

13.1 Terrain resolution model

Terrain resolution is distance-based on both sides of the closed track loop. This means the same rule is applied to topological interior terrain, ordinary exterior terrain, and exterior pockets that are almost surrounded by the track.

For each unconstrained terrain point, trackgen finds the closest sampled track boundary segment. The target spacing is conceptually:

spacing_floor = min(track_step, border_step)
near_track_spacing = max(projected_boundary_spacing, spacing_floor)
factor = clamp(distance_from_track / terrain_transition, 0, 1)
spacing = near_track_spacing
        + max(0, border_step - near_track_spacing) * factor

Consequences:

At the track boundary, terrain retains the local fine spacing established by track-boundary sampling and constraints.
Short boundary edges are retained to follow tight curves, but their small chord lengths are not propagated below min(track step, border step) into the unconstrained terrain.
When border step is larger than the local spacing, the target reaches border step at terrain transition metres from the nearest track boundary.
Farther away, target spacing remains at the resulting coarse value, normally border step.
Narrow gaps stay relatively detailed because every point in the gap remains close to at least one track boundary.
Broad infields and broad exterior pockets become coarser even when they are enclosed by track on several sides.
If border step is not larger than the local near-track spacing, the transition does not force a finer or coarser value there.

The generated road, side, border, barrier, and collision geometry are not changed by this parameter. It controls refinement of the surrounding terrain mesh.

13.2 Defaults and disabling the transition

If terrain transition is omitted, it defaults to border margin. This provides a gradual transition over approximately the same scale as the generated outer terrain extent.

A non-positive value disables distance-based spacing and retains the legacy EasyMesh spacing interpolation:

Legacy behavior can leave large interior or almost-enclosed exterior regions finer than necessary because those regions have no nearby coarse boundary from which to interpolate.

13.3 Example values and impact

Assume that the effective near-track spacing is 10 m and border step is 40 m:

`terrain transition`	Result	Typical impact
`50 m`	Spacing reaches `40 m` only `50 m` from the track; halfway it is about `25 m`.	Aggressive polygon reduction and fast generation, but less elevation detail away from the road.
`150 m`	Spacing is about `25 m` at `75 m` and reaches `40 m` at `150 m`.	Balanced starting point for many medium-sized tracks.
`300 m`	Spacing is about `25 m` at `150 m` and reaches `40 m` at `300 m`.	Gradual falloff with more distant elevation detail, more triangles, and longer generation time.
`0 m`	Distance-based spacing is disabled.	Legacy output; potentially much denser in large infields and enclosed exterior pockets.

For the mini example in chapter 11, track step="8", border step="16", and terrain transition="140" produce a gentle transition. If the effective near-track spacing is approximately 8 m, the target is approximately 12 m at 70 m from the track and 16 m at 140 m or farther away.

Practical tuning:

Reduce track step when the terrain edge does not follow curves or side geometry closely enough, or when finer terrain is needed immediately beside the track. This increases boundary samples and usually increases mesh size.
Increase border step to reduce far-field triangle density.
Reduce terrain transition to reach the coarse spacing sooner.
Increase terrain transition when distant elevation-map features look too faceted or broad height changes need more geometric detail.
Keep terrain transition larger than the near-track safety/detail zone you want to preserve.
Regenerate and inspect both large infields and concave exterior pockets after changing these values. A valid mesh can still be visually too coarse for a particular elevation map.

How elevation map is used:

grayscale is sampled over track bounding box plus margin
darker -> lower, brighter -> higher
mapped to [minimum altitude, maximum altitude]

Important operational detail:

when trackgen is invoked with -E, terrain loading path skips elevation-map loading and runs export flow (see chapters 14 and code path in GenerateTerrain).

13.4 Automatic grade-separated crossings

trackgen automatically generates bridges where the track crosses over itself. The upper road must be high enough for the bridge underside to clear the lower road, its sides, borders, and barriers.

Generate the track and surrounding terrain together with:

trackgen -c <category> -n <name> -a

The optional dimensions belong in Graphic/Terrain Generation:

crossing bridge socket gap: lateral clearance between each side of the lower track and its bridge support wall. Default 0.5 m; zero is allowed.
crossing bridge thickness: minimum thickness below the upper road surface. Default 1.0 m; must be positive. Increasing it requires more vertical separation between the roads.

Both values must be finite; negative gaps and non-positive thicknesses stop generation with an error.

trackgen reports how many crossings it found and how many bridges it generated. If a bridge is missing, check vertical clearance and the crossing angle: level crossings, nearly tangent crossings, and unsuitable local geometry may be skipped.

Crossing materials

Four optional Graphic/Terrain Generation selectors refer to entries in Surfaces:

underside controls the bottom of the bridge, side its outer vertical faces, socket the support walls beside the lower road, and floor the strips between that road and the support walls.

Selector	Default surface / texture	Nominal U x V size
`crossing bridge underside surface`	`bridge-underside` / `bridge-underside.png`	14 x 7 m
`crossing bridge side surface`	`bridge-side` / `bridge-side.png`	14 x 7 m
`crossing bridge socket surface`	`bridge-socket` / `bridge-socket.png`	14 x 7 m
`crossing bridge floor surface`	`bridge-floor` / `bridge-floor.png`	4 x 4 m

The defaults are supplied by the shared surface catalog. To override a material, define a surface and select it, for example:

<section name="Surfaces">
  <section name="my-bridge-concrete">
    <attstr name="texture name" val="my-concrete.png"/>
    <attnum name="texture size" unit="m" val="14"/>
    <attnum name="texture size v" unit="m" val="7"/>
  </section>
</section>
<section name="Graphic">
  <section name="Terrain Generation">
    <attnum name="crossing bridge socket gap" unit="m" val="0.5"/>
    <attnum name="crossing bridge thickness" unit="m" val="1.0"/>
    <attstr name="crossing bridge socket surface" val="my-bridge-concrete"/>
  </section>
</section>

Merge these entries into the existing sections and supply my-concrete.png in the track directory or shared texture path. texture size is nominal U size; texture size v is nominal V size and defaults to U. Independent V sizing applies to the crossing mapper, not existing road or terrain mapping. Missing/empty texture definitions fall back to the existing concrete material, or to the adjacent lower-track boundary material for floors. An invalid U size uses the fallback material's positive size; a missing or invalid V size uses U.

Texture mapping and fitting

texture size and texture size v specify the physical width and height of a texture tile in metres. Increasing them makes the pattern larger.

Underside: U runs across the upper road and V along it. A narrow bridge crops the image; a bridge wider than the U size enlarges the image proportionally to fit the width. The texture can repeat along the bridge.
Bridge sides and support walls: U runs horizontally and V vertically. Short walls crop the image. Walls taller than the V size enlarge it proportionally to fit the height, preserving its aspect ratio. The texture can repeat horizontally.
Floor strips beside the lower road: U runs along the lower road and V across it. Both directions repeat at the configured sizes.

14. trackgen -E elevation export modes

-E <n> writes elevation PNG outputs. The mode number selects which image(s) are written.

14.1 Numeric mode meaning

Supported values:

0: export all four maps (-elv, -elv2, -elv3, -elv4) in one run.
1: export continuous grayscale height map from the combined generated scene AC.
2: export continuous grayscale height map from terrain mesh AC (-msh).
3: export occupancy-style map from terrain mesh AC (track/terrain footprint dark, outside white).
4: export quantized (stepped) grayscale height map from track AC (-trk).

14.2 Output filenames and behavior

From current implementation:

mode 1 (or 0) -> <name>-elv.png
mode 2 (or 0) -> <name>-elv2.png
mode 3 (or 0) -> <name>-elv3.png
mode 4 (or 0) -> <name>-elv4.png

Generation mapping in code:

-elv.png: continuous grayscale altitude map from <name>.ac (dispf=1).
-elv2.png: continuous grayscale altitude map from <name>-msh.ac (dispf=1).
-elv3.png: coverage mask from <name>-msh.ac (dispf=0):
- mesh-hit pixels are dark
- no-mesh pixels are white
-elv4.png: stepped altitude map from <name>-trk.ac (dispf=2), using -H bins.

Practical reading of the images:

brighter pixel means higher altitude (for dispf=1 and dispf=2 maps)
-elv3.png is best for "where geometry exists" checking, not for exact altitude

14.3 -H interaction

-H <nb> sets quantization count for mode 4.
Larger values: finer altitude bands.
Smaller values: coarser stepped map.

14.4 Typical use cases

mode 1: single-image altitude overview after a generation pass
mode 2: inspect terrain-mesh-specific altitude without track-only export path
mode 3: create/edit masks and verify terrain coverage extents quickly
mode 4: produce banded contour-style map for manual elevation editing workflow
mode 0: generate complete diagnostic set for comparison

15. Pits and cameras

Pits

Main Track/Pits typically uses:

entry, start, end, exit
side
speed limit
length, width

entry, start, end, and exit refer to segment names. Keep those names unique and stable.

Cameras

Common camera fields:

segment
to right
to start
height
fov start, fov end (field of view)

On turns, many tracks use unit="deg" for to start.

16. Units and numeric interpretation

TORCS parameter handling converts values with unit=... to SI internally.

Examples:

deg -> radians
% or percent -> divide by 100
km, cm, mm, ft, in -> meters

Implications for authors:

Keep units explicit in XML for readability.
Understand that final stored values are SI.
Be careful when comparing raw XML values against debug prints in different layers.

17. Advanced fields and compatibility notes

Advanced per-segment fields used by loader include:

env map index
marks

Notes:

env map index feeds environment mapping selection in graphics modules.
marks defines turn-marker sign distances (for example 25;50;100) used by trackgen turn-mark generation in extension build paths.

18. Reference tables

For a compact applied example that uses many keys from these tables together, see 11.1 Mini end-to-end XML example.

18.1 Segment geometry core keys

Key	Scope	Meaning	Default/Fallback
`type`	segment	geometry kind: `str` straight, `lft` left turn, `rgt` right turn	required
`lg`	`str`	straight length	required for `str`
`radius`	`lft/rgt`	start radius	required for `lft/rgt`
`end radius`	`lft/rgt`	end radius (varying-radius turn)	defaults to `radius`
`arc`	`lft/rgt`	turn angle	required for `lft/rgt`
`z start`	segment	center start height	overrides side start heights
`z end`	segment	center end height	preferred end-height source
`z start left/right`	segment	side-specific start heights	used when `z start` is absent
`z end left/right`	segment	side-specific end heights	used when `z end` is absent
`grade`	segment	longitudinal slope	used when `z end` is absent
`banking start/end`	segment	cross-slope angles	applied to side heights where provided
`profil`	segment	vertical interpolation mode	defaults to `spline`
`profil steps`	segment	split count hint	if `1`, may derive from step length
`profil steps length`	segment/main	target split length	segment value or main-track fallback
`profil ... tangent ...`	segment	spline shape control	side-specific or generic override
`surface`	segment	material/surface name	previous segment; initially `Main Track/surface`

18.2 Side/border/barrier keys

Element	Key set	Behavior
side	`start width`, `width`, `end width`, `surface`, `banking type`	supports continuous width interpolation within segment
border	`width`, `height`, `surface`, `style`	width is constant per authored segment
barrier	`width`, `height`, `surface`, `style`	collision boundary layer outside side/border

Side width fallback chain:

start width <- previous side end width when omitted
width <- start width when omitted
end width <- width when omitted

Style values seen in loader:

border style: plan, curb, wall
barrier style: fence, wall

Style behavior notes:

curb: height acts as cross-width elevation offset (wheel-height relevant)
wall: height defines vertical wall extrusion; used by wall collision solids
plan: flat strip behavior without curb/wall-specific offset semantics

18.3 Surface keys

Key	Category	Meaning
`friction`	physics	grip coefficient
`rolling resistance`	physics	rolling drag factor
`roughness`	physics	disturbance amplitude parameter
`roughness wavelength`	physics	disturbance spatial wavelength
`dammage`	physics	damage factor
`rebound`	physics	restitution-like factor
`texture name`	rendering	base texture
`texture type`	rendering	`continuous` or `discrete` mapping behavior
`texture link with previous`	rendering	continuity across segment boundaries
`texture start on boundary`	rendering	reset texture origin at boundaries
`texture size`	rendering	texture repeat scale
`texture size v`	crossing rendering	independent nominal V size; defaults to `texture size`; see section 13.4 for fitting rules
`texture mipmap`	rendering	mipmap hint value
`bump name`, `bump size`	rendering	bump-texture and scale
`raceline name`	rendering	raceline overlay texture
`color R1/G1/B1`, `R2/G2/B2`	rendering	color channels for surface definitions

18.4 Terrain generation keys

Key	Meaning
`track step`	track-boundary sampling step and lower limit for spacing propagated from dense boundary points, capped by `border step`
`border margin`	terrain extent around track bounds
`border step`	coarse target spacing away from the track
`terrain transition`	distance over which terrain spacing grows from near-track spacing to `border step`; defaults to `border margin`, non-positive disables it
`crossing bridge socket gap`	lateral clearance outside lower-track sides; finite and non-negative, default 0.5 m
`crossing bridge thickness`	minimum thickness below the upper road; finite and positive, default 1.0 m
`crossing bridge underside surface`	underside material; default `bridge-underside`
`crossing bridge side surface`	fascia and coplanar portal-extension material; default `bridge-side`
`crossing bridge socket surface`	socket wall and filler material; default `bridge-socket`
`crossing bridge floor surface`	lower floor-strip material; default `bridge-floor`
`border height`	border wall/height parameter
`group size`	terrain grouping granularity
`surface`	base terrain material
`relief file`	optional relief geometry constraints
`elevation map`	grayscale input map for altitude shaping
`maximum altitude` / `minimum altitude`	map grayscale to world-height range

18.5 Tool option recap

trackgen: -a -s -S -b -r -z -B -E -H -i -o
accc: +o +shad -g -l0 -l1 -l2 -l3 -d1 -d2 -d3 -S -es -nts

19. Author checklist

Before generation/testing:

XML version is 4.
Segment names used by pits/cameras exist exactly.
Every turn has radius and arc.
Expected profile step count is known for critical segments.
Side taper is on side sections, not border.
Surface names referenced by segments exist in Surfaces.
Terrain settings (track step, border step, terrain transition, margins, and altitude range) are intentional.
XML header metadata (author, description) is present and accurate.
README contains explicit license and attribution for XML, models, and textures.
No third-party assets with unknown or incompatible license terms are included.

After changes:

regenerate with trackgen
run optional accc post-processing if needed
test in-game for seams, banking transitions, runoff feel, pit behavior, and cameras

Author: Bernhard Wymann