TIRE(nged)

NAME

tire - Generate tire and optional wheel geometry from tire dimensions.

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SYNOPSIS
DESCRIPTION
OPTIONS
CUSTOM TREAD JSON
GENERATED OBJECTS
EXAMPLES
AUTHOR
BUG REPORTS

SYNOPSIS

tire [options]
tire --demo-file tire_demo.g

DESCRIPTION

The tire command generates tire geometry, and optionally wheel geometry, using either ISO-style tire dimensions or explicit dimensional parameters.

The command accepts explicit ISO inputs via -d or --dimensions and also accepts the synonymous long form --ISO. The supported ISO form is width-mm/aspect-percent_R_rim-diameter-in, for example 235/75R15.

OPTIONS

-h, -?, --help: Print help and exit.
-n, --obj-name name: Set the top-level object name.
-w, --wheel bool: Enable or disable wheel generation.
-d, --dimensions ISO_tire_spec: Specify tire dimensions using ISO-style inputs.
--ISO ISO_tire_spec: Synonym for --dimensions.
-W, --width mm: Set tire width in millimeters. Overrides ISO dimensions.
-R, --aspect-ratio ratio: Set aspect ratio as ratio/100. Overrides ISO dimensions.
-D, --rim-diameter inches: Set rim diameter in inches. Overrides ISO dimensions.
-g, --tread-depth value: Set tread depth in 1/32 inch units.
-j, --hub-width inches: Set rim width.
-s, --max-sidewall-radius mm: Set the maximum sidewall radius.
-u, --tire-thickness mm: Set tire thickness.
-p, --tread-pattern name: Set the tread pattern preset name. Legacy aliases 1 and 2 are accepted.
-c, --tread-pattern-cnt count: Override the number of tread patterns around the tire. Named presets provide default counts. Each preset has a pattern-aware valid range so lug and block designs remain visually plausible; values outside that range are rejected.
-t, --tread-shape id: Set the tread shape profile identifier.
--tread-pattern-file file: Read a custom JSON tread pattern definition. The object must specify type and symmetry. Supported optional fields are $schema, schema_version, id, description, terrain, axle, void, grooves, groove_angle, block, pitch, pitch_seq, sipes, shoulder, center, tie_bars, shape, pattern_count, and sketches. Unknown fields are rejected.
--list-tread-patterns: List available tread pattern presets and exit.
--demo-file file.g: Generate a sampler grid of varied tire examples. When run from MGED, the sampler is written to the current database; when run as the standalone tire(1) program, the database filename is taken from file.g. The sampler creates an all combination that arranges compact-car, sedan, performance, SUV, van, pickup, commercial truck, bus, farm tractor, wheel-loader, and mining haul-truck tire assemblies 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 supported 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. The other pattern fields are retained as documented metadata for round-trip editing, but they do not alter the supplied polygons. Each polygon must have at least three points, and each point is a two-number array.

GENERATED OBJECTS

The requested tire name is used as the top-level assembly combination. Generated child objects are named below that root using dotted subsystem names, for example name.tire.r, name.air.r, name.wheel.r, name.tire.outer.c, and name.tread.master.c. Indexed tread, bolt, and hub-hole objects use zero-padded numeric suffixes so database listings sort in generation order.

The top-level assembly combination stores the resolved generation settings as attributes with the tire:: prefix. These include the normalized ISO size, wheel and tread enable flags, tread pattern source and count, tread depth, derived radii and widths, and tire thickness. If tread is generated, the resolved tread pattern JSON is stored as tire::tread_pattern_json so the pattern can be inspected, copied, and modified later.

When --demo-file is used, the generated all combination references the individual named tire assemblies with placement transforms for visual comparison. The individual assemblies remain available by their vehicle-target names, such as compact_car, pickup_truck, and mining_haul_truck.

EXAMPLES

Example 1. Create a tire from ISO dimensions.

mged> tire --obj-name tire_235_75r15 --dimensions 235/75R15

Generates tire geometry named tire_235_75r15 using the specified ISO tire size.

Example 2. Create a mud-terrain treaded tire.

mged> tire --obj-name tire_mt --dimensions 235/75R15 --tread-pattern mud-terrain

Generates tire geometry using the built-in mud-terrain tread preset.

Example 3. Create the built-in tire sampler.

mged> tire --demo-file tire_demo.g

Generates the sampler objects and top-level all combination in the current database.

AUTHOR

BRL-CAD Team

BUG REPORTS

Reports of bugs or problems should be submitted via electronic mail to devs@brlcad.org