229 lines
8.6 KiB
C++
229 lines
8.6 KiB
C++
#pragma once
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#include "geometry.h"
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#include <algorithm>
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#include <chrono>
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#include <glm/glm.hpp>
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#include <iostream>
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#include <string>
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#include <vector>
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class KDTree {
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public:
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KDTree(std::vector<Point *> points) {
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std::cout << "Building tree with " << points.size() << " points took ";
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auto start = std::chrono::high_resolution_clock::now();
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root = build(points, 0);
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auto end = std::chrono::high_resolution_clock::now();
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std::cout << std::chrono::duration_cast<std::chrono::microseconds>(end - start).count()
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<< " microseconds" << std::endl;
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}
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~KDTree() = default; // TODO: Delete all allocated Nodes
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const Triangle *intersect_ray(const Ray ray, Vector &result) {
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auto start = std::chrono::high_resolution_clock::now();
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float nearest = 1000.0; // Initial max distance
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const Triangle *nearest_triangle = nullptr;
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intersect_ray_recurse(nearest_triangle, result, ray, root, 0, nearest);
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auto end = std::chrono::high_resolution_clock::now();
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std::cout << "Intersection took "
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<< std::chrono::duration_cast<std::chrono::microseconds>(end - start).count()
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<< " microseconds" << std::endl;
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return nearest_triangle;
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}
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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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std::vector<Vector> get_lines() {
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std::vector<Vector> lines;
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float mins[3] = {-1000, -1000, -1000};
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float maxs[3] = {1000, 1000, 1000};
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get_lines_recursive(lines, root, mins, maxs);
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return lines;
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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->pos[axis] < p2->pos[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::min_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->pos[it_axis] - min->pos[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 + 1, 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 intersect_ray_recurse(const Triangle *&nearest_triangle, Vector &result, Ray ray,
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Node *node, int depth, float &nearest) {
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// Exit condition: This node was iterated towards, but does not exist
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if (node == nullptr) { return; }
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// Check for a collision here
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// Iterate over all Triangles which this Point is involved in
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for (const Triangle *triangle : node->point->triangles) {
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Vector current_result(0, 0, 0);
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float current_distance;
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// If we have a collision, and it is closer to the ray origin than the closest previous
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// collision, remember it
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if (ray.intersects_triangle(triangle, current_result, current_distance)) {
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if (current_distance < nearest) {
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nearest = current_distance;
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nearest_triangle = triangle;
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result = current_result;
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}
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}
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}
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// Is the ray origin within the left or right child node bounding box?
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Node *near =
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ray.origin[node->axis] > node->point->pos[node->axis] ? node->right : node->left;
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Node *far = near == node->right ? node->left : node->right;
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if (ray.direction[node->axis] == 0.0) {
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// The ray is parallel to the splitting axis, so we only need to check within this box.
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intersect_ray_recurse(nearest_triangle, result, ray, near, depth + 1, nearest);
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} else {
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// Calculate the distance from the ray origin to the splitting axis
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float t =
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(node->point->pos[node->axis] - ray.origin[node->axis]) / ray.direction[node->axis];
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// Check this side for intersections up to the distance of the currently best
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// intersection
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intersect_ray_recurse(nearest_triangle, result, ray, near, depth + 1, nearest);
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// If the far side is closer than the distance to the best current intersection, check
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// that side too
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if (t < nearest) {
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intersect_ray_recurse(nearest_triangle, result, ray, far, depth + 1, nearest);
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}
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}
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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 * 2, ' ') + std::to_string(point->pos[0]) + ", " +
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std::to_string(point->pos[1]) + ", " + std::to_string(point->pos[2]) +
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" with axis " + std::to_string(node->axis) + "\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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void get_lines_recursive(std::vector<Vector> &lines, Node *node, float mins[3], float maxs[3]) {
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if (node == nullptr) return;
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int axis = node->axis;
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// Add lines for this node
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// We add a whole bounding box, so we need 8 points -> 12 lines
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lines.emplace_back(Vector(mins[0], mins[1], mins[2]));
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lines.emplace_back(Vector(maxs[0], mins[1], mins[2]));
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lines.emplace_back(Vector(maxs[0], mins[1], mins[2]));
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lines.emplace_back(Vector(maxs[0], maxs[1], mins[2]));
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lines.emplace_back(Vector(maxs[0], maxs[1], mins[2]));
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lines.emplace_back(Vector(mins[0], maxs[1], mins[2]));
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lines.emplace_back(Vector(mins[0], maxs[1], mins[2]));
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lines.emplace_back(Vector(mins[0], mins[1], mins[2]));
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lines.emplace_back(Vector(mins[0], mins[1], maxs[2]));
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lines.emplace_back(Vector(maxs[0], mins[1], maxs[2]));
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lines.emplace_back(Vector(maxs[0], mins[1], maxs[2]));
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lines.emplace_back(Vector(maxs[0], maxs[1], maxs[2]));
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lines.emplace_back(Vector(maxs[0], maxs[1], maxs[2]));
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lines.emplace_back(Vector(mins[0], maxs[1], maxs[2]));
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lines.emplace_back(Vector(mins[0], maxs[1], maxs[2]));
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lines.emplace_back(Vector(mins[0], mins[1], maxs[2]));
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lines.emplace_back(Vector(mins[0], mins[1], mins[2]));
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lines.emplace_back(Vector(mins[0], mins[1], maxs[2]));
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lines.emplace_back(Vector(maxs[0], mins[1], mins[2]));
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lines.emplace_back(Vector(maxs[0], mins[1], maxs[2]));
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lines.emplace_back(Vector(mins[0], maxs[1], mins[2]));
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lines.emplace_back(Vector(mins[0], maxs[1], maxs[2]));
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lines.emplace_back(Vector(maxs[0], maxs[1], mins[2]));
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lines.emplace_back(Vector(maxs[0], maxs[1], maxs[2]));
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// TODO: We don't actually have to add all as some are always going to overlap with the
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// previous lines...
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// Recurse on the left
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float new_maxs[3] = {maxs[0], maxs[1], maxs[2]}; // Copy initially
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new_maxs[axis] = node->point->pos[axis];
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get_lines_recursive(lines, node->left, mins, new_maxs);
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// Recurse on the right
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float new_mins[3] = {mins[0], mins[1], mins[2]}; // Copy initially
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new_mins[axis] = node->point->pos[axis];
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get_lines_recursive(lines, node->right, new_mins, maxs);
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}
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};
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