generated from karl/cpp-template
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80d6a27eef
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6ab6f1fe7b
@ -8,6 +8,5 @@ AllowShortLambdasOnASingleLine: Inline
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AllowShortLoopsOnASingleLine: 'false'
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AllowShortLoopsOnASingleLine: 'false'
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AlwaysBreakBeforeMultilineStrings: 'true'
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AlwaysBreakBeforeMultilineStrings: 'true'
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IndentWidth: '4'
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IndentWidth: '4'
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ColumnLimit: 100
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...
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120
kdtree.h
120
kdtree.h
@ -1,120 +0,0 @@
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#include <algorithm>
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#include <glm/glm.hpp>
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#include <string>
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#include <vector>
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// Forward declarations
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struct Node;
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struct Point;
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struct Triangle;
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struct Node {
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Node(int axis, Point *point, Node *left, Node *right)
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: axis(axis), point(point), left(left), right(right) {}
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int axis;
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Point *point;
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Node *left;
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Node *right;
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};
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struct Triangle {
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Triangle(Point *p1, Point *p2, Point *p3) : p1(p1), p2(p2), p3(p3) {}
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Point *p1;
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Point *p2;
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Point *p3;
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};
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struct Point {
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Point(float coordinates[3], Triangle *triangle)
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: coordinates(coordinates), triangle(triangle) {}
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float *coordinates;
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Triangle *triangle;
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};
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class KDTree {
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public:
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KDTree(std::vector<Point *> points) { root = build(points, 0); }
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~KDTree() = default;
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std::string to_string() {
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std::string str = "";
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to_string_recurse(str, root, 0);
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return str;
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}
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private:
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Node *root;
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int MAX_DEPTH = 500;
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// Returns a comparator lambda for assessing which of the two points has a
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// greater coordinate in the given axis.
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auto get_point_comparator(int axis) {
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return [axis](Point *p1, Point *p2) {
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return p1->coordinates[axis] < p2->coordinates[axis];
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};
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}
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Node *build(std::vector<Point *> points, int depth) {
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// Exit conditions
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if (points.empty() || depth > MAX_DEPTH) { return nullptr; }
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// Select axis by choosing the one with maximal extent
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float max_extent = 0;
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int axis = 0;
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for (int it_axis = 0; it_axis < 3; it_axis++) {
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// Get extent along this axis
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auto comparator = get_point_comparator(it_axis);
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Point *min = *std::max_element(points.begin(), points.end(), comparator);
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Point *max = *std::max_element(points.begin(), points.end(), comparator);
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float extent = max->coordinates[it_axis] - min->coordinates[it_axis];
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// Is it greater than max_extent?
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if (extent > max_extent) {
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// If so, make this the splitting axis
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max_extent = extent;
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axis = it_axis;
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}
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}
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// Choose the median as the pivot and sort the points into
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// left-of-median and right-of-median using nth_element
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int middle = points.size() / 2;
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std::nth_element(points.begin(), points.begin() + middle, points.end(),
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get_point_comparator(axis));
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Point *median = points[middle];
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// TODO: This copies. Can we split the vector into two without copying?
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std::vector<Point *> left_of_median(points.begin(), points.begin() + middle);
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std::vector<Point *> right_of_median(points.begin() + middle, points.end());
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// Create node, recursively call to construct subtree
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return new Node(axis, median, build(left_of_median, depth + 1),
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build(right_of_median, depth + 1));
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}
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void to_string_recurse(std::string &str, Node *node, int depth) {
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if (node == nullptr) { return; }
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Point *point = node->point;
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str += std::string(depth, '-') + std::to_string(point->coordinates[0]) + ", " +
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std::to_string(point->coordinates[1]) + ", " +
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std::to_string(point->coordinates[2]) + "\n";
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to_string_recurse(str, node->left, depth + 1);
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to_string_recurse(str, node->right, depth + 1);
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}
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};
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