Compute bounding box

Primal’s bounding boxes are rectangular right prisms. That is, they are boxes where neighboring walls are at right angles.

The BoundingBox class represents an axis-aligned bounding box, which has two walls perpendicular to the X-axis, two perpendicular to the Y-axis, and two perpendicular to the Z-axis. This is sufficient for many computations; range and intersection operations tend to be fast.

The OrientedBoundingBox class can be oriented in any way with respect to the coordinate axes. This can provide a tighter fit to the bounded data, but construction, intersection, and range calculation are more costly.

Here a group of points is used to create both an (axis-aligned) BoundingBox and an OrientedBoundingBox. The points are drawn in blue, the BoundingBox in black, and the OrientedBoundingBox in orange.

#include "axom/primal/operators/compute_bounding_box.hpp"

  // An array of Points to include in the bounding boxes
  const int nbr_points = 6;
  PointType data[nbr_points] = {PointType {0.6, 1.2, 1.0},
                                PointType {1.3, 1.6, 1.8},
                                PointType {2.9, 2.4, 2.3},
                                PointType {3.2, 3.5, 3.0},
                                PointType {3.6, 3.2, 4.0},
                                PointType {4.3, 4.3, 4.5}};

  // A BoundingBox constructor takes an array of Point objects
  BoundingBoxType bbox(data, nbr_points);
  // Make an OrientedBoundingBox
  OrientedBoundingBoxType obbox = compute_oriented_bounding_box(data, nbr_points);

Primal also provides a merge_boxes() function to produce a bounding box that contains two input bounding boxes. This is available for client codes to use and also supports the operation of the BVHTree class.