Draft

Draft#

A draft is an isolated, in-memory snapshot of an asset’s entity information. It lets you inspect and modify entities (surfaces, edges, volumes, body groups, etc.) locally without mutating the cloud asset.

DraftContext

Context manager that tracks locally modified simulation entities/status.

The draft is created using the create_draft() function. It is meant to be used with the with statement to create a context manager.

with fl.create_draft(new_run_from=geometry) as draft:
    ...

create_draft(*, new_run_from[, ...])

Create a local draft context from a cloud asset for your run.

The draft is responsible primarily for the following:

  • grouping faces, edges and body groups

  • keeping track of all the existen entities

  • managing mirror actions

  • managing coordinate systems

  • analyzing geometry through the oriented bounding box

Access properties#

The properties of the DraftContext that store the geometric entities within the draft are listed below. The entities within those properties can be accessed by name or pattern with the only exception being the imported geometries and surfaces, which can be accessed by index.

DraftContext.body_groups

Return the list of body groups in the draft.

DraftContext.surfaces

Return the list of surfaces in the draft.

DraftContext.mirrored_body_groups

Return the list of mirrored body groups in the draft.

DraftContext.mirrored_surfaces

Return the list of mirrored surfaces in the draft.

DraftContext.edges

Return the list of edges in the draft.

DraftContext.volumes

Return the list of volumes (volume zones) in the draft.

DraftContext.boxes

Return the list of boxes in the draft.

DraftContext.cylinders

Return the list of cylinders in the draft.

DraftContext.imported_geometries

Return the list of imported geometries in the draft.

DraftContext.imported_surfaces

Return the list of imported surfaces in the draft.

Management properties#

Managing mirror actions and coordinate systems is done through the following properties.

DraftContext.coordinate_systems

Coordinate system manager for this draft.

DraftContext.mirror

Mirror manager for this draft.

Those properties provide access to relevant managers.

CoordinateSystemManager

Manage coordinate systems, hierarchy, and entity assignments inside a DraftContext.

MirrorManager

Manage mirror planes and mirrored draft entities inside a DraftContext.

Actions and objects registered through those managers can be modified by directly accessing them through the manager objects.

Example: geometric parameter sensitivity study

with draft:
    draft.coordinate_systems.assign(
        entities=draft.body_groups["body_group_1"],
        coordinate_system=fl.CoordinateSystem(
            name="body_group_1_translation",
            origin=[0, 0, 0] * fl.u.mm,
            axis_of_rotation=(0, 0, 1),
            angle_of_rotation=0 * fl.u.deg,
            scale=(1.0, 1.0, 1.0),
            translation=[20, 0, 0] * fl.u.mm
        )
    )

    prj.run_case(...)

    draft.coordinate_systems.get_by_name("body_group_1_translation").angle_of_rotation = 5*fl.u.deg

    prj.run_case(...)

Important

Mirroring and custom coordinate systems are available only with GeometryAI enabled.

Auditing a selection#

Selectors fail quietly. A glob that matches nothing, or a name whose capitalization does not match the geometry, raises no error – the surfaces simply never appear in any assignment, and the first sign of trouble is a reference area or a boundary condition that covers less than intended. Two draft methods make the selection visible before submission.

DraftContext.preview_selector(selector, *[, ...])

Preview which entities a selector would match in this draft context.

DraftContext.preview_unselected(selection, *)

Report which entities in this draft a selection does not cover.

preview_selector answers “what does this selector match?” for one selector. preview_unselected answers the opposite and more useful question – “what did I miss?” – by reporting every entity in the draft that the given selection does not cover.

with fl.create_draft(new_run_from=geometry, face_grouping="faceId") as draft:
    wheels = fl.SurfaceSelector(name="wheels").match("*rim*")
    body = fl.SurfaceSelector(name="body").match("*body*")

    print(draft.preview_selector(wheels))          # ['front_left_rim', ...]

    missed = draft.preview_unselected([wheels, body])
    if missed:
        raise ValueError(f"No selector covers: {missed}")

The comparison pool is every entity the selection’s kind of selector can reach, read from the same configuration selector expansion itself uses, so the two cannot drift apart. For surfaces that means Surface and MirroredSurface; imported surfaces and ghost boundaries are not selectable and are never reported. The pool spans the whole draft, so surfaces you deliberately left out – wind tunnel walls, for instance – appear in the result and are expected there.

Both accept the same selection forms: a single entity, a single selector, a list mixing the two, or an EntityList (for example my_wall.entities). preview_unselected infers the entity kind from the selection, so the selection must name exactly one kind and must not be empty. By default both return names; pass return_names=False for entity instances.

Note

Both methods are beta and may change in future releases. Each emits a notice once per draft rather than once per call, so they are safe to use in loops.

Computing an oriented bounding box#

For drafts created from a Geometry asset, fl.measure can fit an oriented bounding box (OBB) to a set of surfaces using the underlying tessellation data. The box is aligned with the natural axes of the selected surfaces (via principal component analysis) rather than the global coordinate axes, and gives the center, principal axes and extents of cylindrical components such as wheels. From that box a rotation axis and radius can be derived to drive a rotating wall boundary condition or a rotating reference frame.

measure.oriented_bounding_box(draft, *, surfaces)

Compute a PCA-oriented bounding box for selected geometry surfaces.

oriented_bounding_box returns an OBBResult describing the box geometry only: center, axes and extents. The rotation axis and radius are obtained separately through OBBResult.get_rotation_axis_and_radius(), which returns a RotationAxisAndRadius. The axis is selected with either a rotation_axis_hint direction or an explicit axis_index (0, 1 or 2). Passing both, an out-of-range index, or a zero hint raises Flow360ValueError; if neither is given the axis is inferred from the most circular cross-section and a warning is emitted.

OBBResult

Oriented Bounding Box computed from a point cloud.

RotationAxisAndRadius

Rotation axis and averaged radius derived from an oriented bounding box.

Note

fl.measure.oriented_bounding_box requires a draft created from a Geometry resource. Drafts created from a surface mesh or volume mesh do not carry the tessellation data the bounding box is computed from.

DraftContext.compute_obb() is a deprecated wrapper around fl.measure.oriented_bounding_box() and is scheduled for removal in release 26.

See also