# BoundingBoxTree¶

class dolfin.cpp.mesh.BoundingBoxTree

Bases: object

This class implements a (distributed) axis aligned bounding box tree (AABB tree). Bounding box trees can be created from meshes and [other data structures, to be filled in].

Create empty bounding box tree

build()

• build(mesh)

Build bounding box tree for cells of mesh.

Arguments
mesh (Mesh)

The mesh for which to compute the bounding box tree.

• build(mesh, tdim)

Build bounding box tree for mesh entities of given dimension.

Arguments
mesh (Mesh)

The mesh for which to compute the bounding box tree.

dimension (int)

The entity dimension (topological dimension) for which to compute the bounding box tree.

• build(points, gdim)

Build bounding box tree for point cloud.

Arguments
points (list of Point)

The list of points.

gdim (int)

The geometric dimension.

collides()

Check whether given point collides with the bounding box tree. This is equivalent to calling compute_first_collision and checking whether any collision was detected.

Returns
bool
True iff the point is inside the tree.
collides_entity()

Check whether given point collides with any entity contained in the bounding box tree. This is equivalent to calling compute_first_entity_collision and checking whether any collision was detected.

Returns
bool
True iff the point is inside the tree.
compute_closest_entity()

Compute closest entity to Point.

Returns
int
The local index for the entity that is closest to the point. If more than one entity is at the same distance (or point contained in entity), then the first entity is returned.
double
The distance to the closest entity.
Arguments
point (Point)
The point.
compute_closest_point()

Compute closest point to Point. This function assumes that the tree has been built for a point cloud.

Developer note: This function should not be confused with computing the closest point in all entities of a mesh. That function could be added with relative ease since we actually compute the closest points to get the distance in the above function (compute_closest_entity) inside the specialized implementations in TetrahedronCell.cpp etc.

Returns
int
The local index for the point that is closest to the point. If more than one point is at the same distance (or point contained in entity), then the first point is returned.
double
The distance to the closest point.
Arguments
point (Point)
The point.
compute_collisions()

• compute_collisions(point)

Compute all collisions between bounding boxes and Point.

Returns
numpy.array(int)

A list of local indices for entities contained in (leaf) bounding boxes that collide with (intersect) the given point.

Arguments
point (Point)

The point.

• compute_collisions(tree)

Compute all collisions between bounding boxes and BoundingBoxTree.

Returns
numpy.array(int)

A list of local indices for entities in this tree that collide with (intersect) entities in other tree.

std::vector<unsigned int>

A list of local indices for entities in other tree that collide with (intersect) entities in this tree.

The two lists have equal length and contain matching entities, such that entity i in the first list collides with entity i in the second list.

Note that this means that the entity lists may contain duplicate entities since a single entity may collide with several different entities.

Arguments
tree (BoundingBoxTree)

The bounding box tree.

Note that this function only checks collisions between bounding boxes of entities. It does not check that the entities themselves actually collide. To compute entity collisions, use the function compute_entity_collisions.

compute_entity_collisions()

• compute_entity_collisions(point)

Compute all collisions between entities and Point.

Returns
numpy.array(int)

A list of local indices for entities that collide with (intersect) the given point.

Arguments
point (Point)

The point.

• compute_entity_collisions(tree)

Compute all collisions between entities and BoundingBoxTree.

Returns
numpy.array(int)

A list of local indices for entities in this tree that collide with (intersect) entities in other tree.

std::vector<unsigned int>

A list of local indices for entities in other tree that collide with (intersect) entities in this tree.

The two lists have equal length and contain matching entities, such that entity i in the first list collides with entity i in the second list.

Note that this means that the entity lists may contain duplicate entities since a single entity may collide with several different entities.

Arguments
tree (BoundingBoxTree)

The bounding box tree.

compute_first_collision()

Compute first collision between bounding boxes and Point.

Returns
int
The local index for the first found entity contained in a (leaf) bounding box that collides with (intersects) the given point. If not found, std::numeric_limits<unsigned int>::max() is returned.
Arguments
point (Point)
The point.
compute_first_entity_collision()

Compute first collision between entities and Point.

Returns
int
The local index for the first found entity that collides with (intersects) the given point. If not found, std::numeric_limits<unsigned int>::max() is returned.
Arguments
point (Point)
The point.
compute_process_collisions()

Compute all collisions between process bounding boxes and Point. Effectively a list of processes which may contain the Point.

Returns
numpy.array(int)
A list of process numbers where the Mesh may collide with (intersect) the given point.
Arguments
point (Point)
The point.
thisown

The membership flag