Quadtree data structure in Common Lisp
Quadtree is quadtree data structure in Common Lisp.
Here shows how to store points into a quadtree.
First, define point structure.
(defstruct (point (:constructor make-point (x y))) (x 0d0 :read-only t) (y 0d0 :read-only t))
Then, implement an intersection test method for the point structure, which is called when inserting points to a quadtree.
(defmethod quadtree:intersect-p (quadtree (point point)) (destructuring-bind (x0 y0 x1 y1) (quadtree:boundary quadtree) (let ((x (point-x point)) (y (point-y point))) (and (<= x0 x x1) (<= y0 y y1)))))
Now, make and bulid a quadtree with its boundary, query it to get points stored in the leaf that contains specified
(let ((points (list (make-point 0.0d0 0.0d0) (make-point 1.0d0 1.0d0) (make-point 0.1d0 0.1d0) (make-point 0.1d0 0.2d0) (make-point 0.2d0 0.1d0) (make-point 0.2d0 0.2d0) (make-point 0.2d0 0.3d0) (make-point 0.2d0 0.4d0) (make-point 0.3d0 0.2d0) (make-point 0.3d0 0.3d0)))) ;; make a quadtree with its boundary (let ((qt (quadtree:make 0.0d0 0.0d0 1.0d0 1.0d0))) ;; build the quadtree (loop for point in points do (quadtree:insert qt point)) ;; query the quadtree (is (length (quadtree:query qt 0.1 0.1)) 5)))
Since quadtree is just requesting to Quicklisp, plese use its local-projects feature for now.
$ cd quicklisp/local-projects $ git clone git://github.com/takagi/quadtree.git
After approved, you can install via Quicklisp.
[Special Variable] *max-depth*
Specifies the maximum depth of a newly created quadtree.
[Special Variable] *max-capacity*
Specifies the maximum capacity of leaves of a newly created quadtree.
MAKE x0 y0 x1 y1 &key max-depth max-capacity => quadtree
Creates an empty quadtree with the boundary of
max-depth specifies the maxinum depth of a quadtree and its default value is provided by
*max-depth* special variable.
max-capacity is the maxinum capacity of a quadtree leaf, subdevided if the value is exceeded, and its default value is provided by
*max-capacity* special variable. However, leaves at the maximum depth contain all inserted objects regardless of the capacity.
INSERT quadtree object => boolean
quadtree. If suceeded, returns
t. Otherwise, returns
nil. The case it fails to inserted an object to a quadtree is that it is out of boundary of the quadtree. If the number of objects in a leaf is exceeded, the leaf is subdevided into four subtrees and its objects are distributed to them.
QUERY quadtree x y &optional neighbor-p => object-list
Queries objects at the point
(x, y) to
nil, returns objects stored in the leaf that contains the point. Otherwise, additionally returns objects stored in leaves neighboring top, bottom, left and right to the leaf that contains the point. The default value of
CLEAR quadtree => boolean
Clears the contents of
quadtree. The return value is always
BOUNDARY quadtree => boundary
Returns the boundary of
quadtree, represented by a list of
y1. It is intended to be used in following
intersect-p function to determine if an object intersects a quadtree.
[Generic Function] intersect-p
INTERSECT-P quadtree object => boolean
object is being inserted to
quadtree which stores objects and returns if
quadtree. Library users should implement this generic function as the object's structure or class they are storing into a quadtree.
- Masayuki Takagi (email@example.com)
Copyright (c) 2015 Masayuki Takagi (firstname.lastname@example.org)
Licensed under the MIT License.