A part as a MuJoCo scene: the triangles quiddity meshed, as an MJCF model.
This is the bridge to a simulated world rather than an exact one. A B-rep can
be ray cast exactly — that is what Quiddity.frame/2 does — but a sensor that
has to make contact, slide and be pushed needs a physics engine. MuJoCo is the
one this writes for, so the part becomes a mesh geometry in metres, which is
what an MJCF holds.
Units
A STEP file is in millimetres and MuJoCo is in metres, so every coordinate is divided by 1000 on the way out. Nothing else is changed: the part keeps the place the file gives it, so a scene written from a part and a frame rendered from the same part agree about where it is, up to that factor.
What it is not
It is not a model of the agent. A scene holds the part; a body, its sensors and its actuators are the experiment's, and putting them here would be a second description of something the experiment already configures.
{:ok, part} = Quiddity.open("bracket.step")
{:ok, xml} = Quiddity.Mjcf.document(part)
File.write!("bracket.xml", xml)Summary
Functions
@spec document(Quiddity.Part.t(), keyword()) :: {:ok, String.t()} | {:error, Quiddity.Error.t()}
The scene as MJCF text.
Options: :deflection (mm, default 0.05), :angular (radians, default 0.3),
:name (the model's name, default "part") and :rgba (the material's colour,
default a neutral grey).
@spec write(Quiddity.Part.t(), Path.t(), keyword()) :: :ok | {:error, Quiddity.Error.t()}
Writes the scene as MJCF text.