Estimate a wheel rotation axis with an OBB

Estimate a wheel rotation axis with an OBB#

This example shows how to use the draft context to fit an oriented bounding box (OBB) to a set of wheel surfaces, then read back the estimated rotation axis, center and radius. These values can be used to configure a rotating wall boundary condition or a rotating reference frame without measuring the geometry by hand.

import flow360 as fl

project = fl.Project.from_cloud("PROJECT_ID_HERE")
geometry = project.geometry

with fl.create_draft(
    new_run_from=geometry,
    face_grouping="face_grouping_tag",
) as draft:

    # Select the surfaces that make up the wheel.
    wheel_surfaces = draft.surfaces["wheel_*"]

    # Fit the oriented bounding box to those surfaces.
    # rotation_axis_hint is optional; when omitted the axis with the most
    # circular cross-section is chosen automatically.
    obb = draft.compute_obb(wheel_surfaces, rotation_axis_hint=[0, 1, 0])

    print("center:", obb.center)
    print("rotation axis:", obb.axis_of_rotation)
    print("radius:", obb.radius)

Notes#

  • compute_obb is available only for drafts created from a Geometry asset. Drafts created from a surface mesh or volume mesh do not carry the tessellation data required to fit the box.

  • entities accepts a single surface, a list of surfaces, or a surface view (e.g. draft.surfaces[...]). Non-surface entities (for example mirrored surfaces) are skipped with a warning.

  • rotation_axis_hint biases the axis selection toward a known direction. When omitted, the axis whose perpendicular cross-section is most circular is used.

  • The returned OBBResult exposes center, axes, extents, axis_of_rotation and radius. When the project has a length unit, the dimensioned fields (center, extents and radius) carry that unit.

Example use cases#

  • Automatic rotation setup for wheels and other cylindrical components

  • Estimating component size and orientation directly from geometry

See also

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