# Box

A box is a rectangular prism defined by its center point and size (dimensions). Boxes can be oriented in three-dimensional space using one of two transformation methods.

# Available Options

Option Description Applicable
Name Identifier for the box always
Center Three-dimensional coordinates of the center point always
Size Dimensions of the box (length, width, height) always
Transform methods Method of defining the box orientation always
Axes Two orthogonal vectors defining orientation Transform methods is Principal Axes
Axis of rotation Rotation axis vector Transform methods is Axis & Angle
Angle of rotation Rotation angle around the axis Transform methods is Axis & Angle

# Detailed Descriptions

# Name

Identifier for the box volume entity.

  • Required

Note: Names are not required to be unique, but using descriptive unique names is recommended for clarity.

# Center

Three-dimensional coordinates (X, Y, Z) defining the center point of the box.

  • Required
  • Units: Length

# Size

Three-dimensional dimensions (length, width, height) of the box along its principal axes.

  • Required
  • Units: Length

Note: The size corresponds to the full extent along each axis, not half-lengths.

# Transform methods

Boxes can be oriented in three-dimensional space using one of two methods:

# Axes

Defines the box orientation using two orthogonal vectors.

  • Required (when using this method)

Notes:

  • The two axes must be orthogonal (perpendicular) to each other
  • First axis (row 1) defines the primary direction (aligns with size X)
  • Second axis (row 2) defines the secondary direction (aligns with size Y)
  • Third axis is automatically computed to complete the right-handed coordinate system

# Axis & Angle

Defines the box orientation using a rotation axis and angle from the default orientation.

# Axis of rotation

The axis vector (X, Y, Z) around which the box is rotated.

  • Default: (0, 0, 1)

Note: The axis is normalized internally.

# Angle of rotation

The angle of rotation around the specified axis.

  • Default: 0 degrees
  • Units: Angle

Note: Positive angles follow the right-hand rule around the rotation axis.

💡 Tips
  • Use boxes for rectangular refinement zones in wakes or regions of interest
  • Align the box with the expected flow direction for wake capture
  • For rotated boxes, the Principal Axes method provides more intuitive control
  • Consider using multiple overlapping boxes for complex L-shaped or T-shaped regions

❓ Frequently Asked Questions

  • What happens if I don't specify orientation?

    The box will align with the global coordinate system axes (no rotation).

  • Can I resize a box after creation?

    Yes, you can modify the size parameters at any time before meshing.

  • How do the axes relate to the size dimensions?

    The first axis corresponds to size[0], the second axis to size[1], and the computed third axis to size[2].

🐍 Python Example Usage

 
import flow360 as fl

# Box using axis and angle rotation
box = fl.Box(
    name="wake_region",
    center=(2, 0, 0) * fl.u.m,
    size=(4, 1, 1) * fl.u.m,
    axis_of_rotation=(0, 1, 0),
    angle_of_rotation=15 * fl.u.deg
)

# Box using principal axes
box_axes = fl.Box.from_principal_axes(
    name="refinement_box",
    center=(0, 0, 0) * fl.u.m,
    size=(2, 1, 0.5) * fl.u.m,
    axes=[(1, 0, 0), (0, 1, 0)]
)

← Cylinder →