Schemas / Simulation

`rig.sim.joint`

v1.0.0 · stable maturity: draft 18 fields 3 required

Fields

Field	Type		Meaning
`kind`	enumfixed · hinge · distance · spring · slider · ball	required	`fixed`, `hinge`, `distance`, `spring`, `slider`, `ball`
`a`	entity	required	First body
`b`	entity	required	Second body
`anchorA`	vec3	optional	Optional. Anchor in `a`'s local space; absent = origin
`anchorB`	vec3	optional	Optional. Anchor in `b`'s local space; absent = origin
`axis`	vec3	optional	Optional. Hinge or slider axis in `a`'s local space; absent = local +Y
`min`	float	optional	Optional. Lower limit. Degrees for `hinge`, distance for `distance` / `slider`. Absent = unlimited
`max`	float	optional	Optional. Upper limit, same units as `min`. Absent = unlimited
`stiffness`	float	optional	Optional. Spring stiffness. Meaningful for `spring`
`damping`	float	optional	Optional. Spring damping. Meaningful for `spring`
`breakForce`	float	optional	Optional. Impulse that breaks the joint. Absent = unbreakable
`collideConnected`	bool	optional	Optional. The two bodies also collide; absent = false
`mimic`	entity	optional	Optional. Joint this one follows
`mimicMultiplier`	float	optional	Optional. Scale on the followed joint's position. Absent = 1
`mimicOffset`	float	optional	Optional. Added after the scale. Same units as `min`. Absent = 0
`swingDegrees`	number0 – *	optional	Optional. Cone from the rest pose. Meaningful for `ball`. Absent = unlimited
`position`	float	optional	Optional. Joint coordinate at load. Degrees for `hinge`, scene units for `slider` and `distance`. Absent = the pose implied by the two transforms
`velocity`	float	optional	Optional. Rate of `position` at load. Degrees per second, or scene units per second. Absent = at rest

Constraint between two bodies. Format when present.

Limits and break thresholds are authored intent. A host that cannot represent a kind skips that joint. A host that finds a mimic cycle skips the mimic. A drive on this joint is rig.sim.actuator.

ball has no single axis and no single position. Its pose is the child transform. swingDegrees is the cone a host may enforce. A fixed joint has no position.

position and velocity are the joint when the document is loaded, the same bargain as a body's velocity. A save of a running robot writes them so another host can continue.

JSON Schema

Resolves at https://rig.works/schemas/rig.sim.joint.schema.json — raw file.

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://rig.works/schemas/rig.sim.joint.schema.json",
  "title": "rig.sim.joint",
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "kind": {
      "type": "string",
      "enum": [
        "fixed",
        "hinge",
        "distance",
        "spring",
        "slider",
        "ball"
      ]
    },
    "a": {
      "$ref": "./_defs.schema.json#/$defs/entity"
    },
    "b": {
      "$ref": "./_defs.schema.json#/$defs/entity"
    },
    "anchorA": {
      "$ref": "./_defs.schema.json#/$defs/vec3"
    },
    "anchorB": {
      "$ref": "./_defs.schema.json#/$defs/vec3"
    },
    "axis": {
      "$ref": "./_defs.schema.json#/$defs/vec3"
    },
    "min": {
      "$ref": "./_defs.schema.json#/$defs/float"
    },
    "max": {
      "$ref": "./_defs.schema.json#/$defs/float"
    },
    "stiffness": {
      "$ref": "./_defs.schema.json#/$defs/float"
    },
    "damping": {
      "$ref": "./_defs.schema.json#/$defs/float"
    },
    "breakForce": {
      "$ref": "./_defs.schema.json#/$defs/float"
    },
    "collideConnected": {
      "$ref": "./_defs.schema.json#/$defs/bool"
    },
    "mimic": {
      "$ref": "./_defs.schema.json#/$defs/entity"
    },
    "mimicMultiplier": {
      "$ref": "./_defs.schema.json#/$defs/float"
    },
    "mimicOffset": {
      "$ref": "./_defs.schema.json#/$defs/float"
    },
    "swingDegrees": {
      "type": "number",
      "minimum": 0
    },
    "position": {
      "$ref": "./_defs.schema.json#/$defs/float"
    },
    "velocity": {
      "$ref": "./_defs.schema.json#/$defs/float"
    }
  },
  "required": [
    "kind",
    "a",
    "b"
  ],
  "x-rig-maturity": "draft"
}

Seen in

play-scene.json · robot-lab.json · robot-lesson.json