TIRE(1)

NAME

tire - generate a parametric tire model from standard tire dimensions

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SYNOPSIS
DESCRIPTION
OPTIONS
CUSTOM TREAD JSON
EXAMPLES
SEE ALSO
AUTHOR
COPYRIGHT
BUG REPORTS

SYNOPSIS

tire [options] [obj_name]
tire --list-tread-patterns
tire --demo-file _file.g_

tire creates a curved-sidewall tire, optionally with a wheel and tread, in the current open database (when run from within mged(1)) or in tire.g when run as a standalone command. Dimensions follow the common ISO notation (for example 235/75R15): width in millimeters, sidewall aspect ratio as a percentage, and rim diameter in inches. With no options the default size is 215/55R17 and the wheel is included.

By default tire does not model tread, since tread geometry can significantly increase raytracing times. Tread is enabled by selecting a named preset with -p, supplying a custom JSON definition with --tread-pattern-file, or choosing a legacy shape with -t. The generated assembly stores its resolved settings as tire:: attributes on the top-level combination, including the normalized ISO size and (when tread is generated) the resolved tread pattern JSON.

The generated models are intended for procedural geometry, visualization, inspection, and BRL-CAD workflow testing. They are not validated for tire engineering design, roadworthiness, load rating, manufacturing, regulatory compliance, or vehicle safety use.

If no obj_name is given (and -n is not used), a name of the form tire-215-55R17 is derived from the resolved dimensions.

OPTIONS

-h, -?: Print a help message and exit. Use --list-tread-patterns to see the available tread presets.
-n name: Set the name of the top-level database object. The same value is used as the suffix for generated child objects.
-w bool: Enable (1) or disable (0) the wheel. The wheel is included by default.
-d width/aspectRdiameter: Specify tire dimensions using ISO-style notation, for example 235/75R15. Width is in mm, aspect ratio in percent, and rim diameter in inches.
-W #: Tire width in mm, allowing fractional values. Overrides the width from -d.
-R #: Sidewall aspect ratio (percent), allowing fractional values. Overrides the ratio from -d.
-D #: Rim diameter in inches, allowing fractional values. Overrides the diameter from -d.
-g #: Tread depth in 32nds of an inch (for example, 11 means 11/32 in). The default is 11.
-j #: Rim (hub) width in inches.
-s #: Maximum sidewall radius in mm, measured from the tire center to the widest point of the sidewall. Must lie between the rim radius and the tire radius.
-u #: Tire (wall) thickness in mm.
-p name: Select a named tread pattern preset (see --list-tread-patterns). The legacy aliases 1 and 2 map to the legacy-rib and legacy-block presets. Mutually exclusive with --tread-pattern-file.
-c #: Number of tread patterns repeated around the tire. Each preset has its own valid range (overall 3 to 512); values outside that range are rejected.
-t #: Legacy tread shape profile (1 or 2). Normally supplied by the selected preset.
--tread-pattern-file file: Read a custom JSON tread pattern definition (see CUSTOM TREAD JSON below). Mutually exclusive with -p.
--list-tread-patterns: List the available named tread presets and exit.
--demo-file file.g: Write a sampler database to file.g and exit. The sampler builds an all combination arranging varied tire examples (compact car, sedan, performance, SUV, van, pickup, commercial truck, bus, tractor, wheel loader, and mining haul truck) in rows by vehicle class and increasing scale.

CUSTOM TREAD JSON

Files supplied with --tread-pattern-file are JSON objects. The required fields are type and symmetry; unknown fields are rejected.

Custom tread JSON field contract

{
  "$schema": "https://brlcad.org/schemas/tire-tread-pattern.schema.json",
  "schema_version": 1,
  "type": "rib | lug | block | hybrid",
  "symmetry": "symmetric | directional | asymmetric",
  "terrain": "HT | AT | MT",
  "axle": "steer | drive | trailer | all",
  "void": "number, 0.1 through 0.7",
  "grooves": "integer, 1 through 8",
  "groove_angle": "number, 0 through 60",
  "block": "small | medium | large",
  "pitch": "uniform | variable | {\"type\":\"variable\",\"count\":2..8}",
  "pitch_seq": ["numbers, each 0.5 through 2.0, 2 through 16 entries"],
  "sipes": "none | low | medium | dense",
  "shoulder": "closed | semi-open | open",
  "center": "continuous | broken | ribbed",
  "tie_bars": false,
  "shape": "integer, 1 or 2",
  "pattern_count": "integer within the selected pattern family's range",
  "sketches": [
    [[0.10, 0.20], [0.24, 0.20], [0.24, 0.80], [0.10, 0.80]]
  ]
}

If sketches is supplied, the listed normalized cut polygons are used as the tread geometry instead of procedurally generated sketches. Each polygon must have at least three points, and each point is a two-number array. The remaining fields are retained as metadata for round-trip editing.

EXAMPLES

Example 1. Creating a 185/65R15 tire with a highway tread

tire -d 185/65R15 -p highway-rib -n autowheel

Generate a 185 mm wide, 65 aspect, 15 in rim tire named autowheel in tire.g, using the built-in highway-rib tread preset. Use --list-tread-patterns to see the other presets such as all-terrain, mud-terrain, and winter-siped.

Example 2. Overriding individual dimensions with fractional values

tire -W 225.5 -R 50 -D 18 -g 13 -c 24 -p mud-terrain -n offroad

Build a precisely sized tire (225.5 mm wide, 50 aspect, 18 in rim) with a 13/32 in tread depth and 24 mud-terrain pattern repeats (each preset has its own valid repeat range). The -W, -R, and -D flags accept fractional input and override any ISO size from -d.

Example 3. Generating the built-in sampler for visual comparison

tire --demo-file tire_demo.g
mged tire_demo.g

Write a database of varied example tires (one per vehicle class) into tire_demo.g, then open it in mged(1). Drawing the all combination shows the full set laid out in rows for side-by-side comparison.