christoph/cpp-masssprings
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build octree async and reuse tree from last frame (disabled as it breaks physics)

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Christoph Urlacher
2026-03-02 18:52:06 +01:00
parent d62d5c78bf
commit 9c48954a78
13 changed files with 329 additions and 273 deletions
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60
src/octree.cpp
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@ -1,7 +1,7 @@
#include "octree.hpp"
#include "config.hpp"
#include "util.hpp"
#include <cfloat>
#include <raymath.h>
#ifdef TRACY
@ -19,16 +19,6 @@ auto octree::node::child_count() const -> int
return child_count;
}
auto octree::create_empty_leaf(const Vector3& box_min, const Vector3& box_max) -> int
{
node n;
n.box_min = box_min;
n.box_max = box_max;
nodes.emplace_back(n);
return static_cast<int>(nodes.size() - 1);
}
auto octree::get_octant(const int node_idx, const Vector3& pos) const -> int
{
const node& n = nodes[node_idx];
@ -75,6 +65,16 @@ auto octree::get_child_bounds(const int node_idx, const int octant) const -> std
return std::make_pair(min, max);
}
auto octree::create_empty_leaf(const Vector3& box_min, const Vector3& box_max) -> int
{
node n;
n.box_min = box_min;
n.box_max = box_max;
nodes.emplace_back(n);
return static_cast<int>(nodes.size() - 1);
}
auto octree::insert(const int node_idx, const int mass_id, const Vector3& pos, const float mass,
const int depth) -> void
{
@ -153,6 +153,44 @@ auto octree::insert(const int node_idx, const int mass_id, const Vector3& pos, c
nodes[node_idx].mass_total = new_mass;
}
auto octree::build_octree(octree& t, const std::vector<Vector3>& positions) -> void
{
#ifdef TRACY
ZoneScoped;
#endif
t.nodes.clear();
t.nodes.reserve(positions.size() * 2);
// Compute bounding box around all masses
Vector3 min{FLT_MAX, FLT_MAX, FLT_MAX};
Vector3 max{-FLT_MAX, -FLT_MAX, -FLT_MAX};
for (const auto& [x, y, z] : positions) {
min.x = std::min(min.x, x);
max.x = std::max(max.x, x);
min.y = std::min(min.y, y);
max.y = std::max(max.y, y);
min.z = std::min(min.z, z);
max.z = std::max(max.z, z);
}
// Pad the bounding box
constexpr float pad = 1.0;
min = Vector3Subtract(min, Vector3Scale(Vector3One(), pad));
max = Vector3Add(max, Vector3Scale(Vector3One(), pad));
// Make it cubic (so subdivisions are balanced)
const float max_extent = std::max({max.x - min.x, max.y - min.y, max.z - min.z});
max = Vector3Add(min, Vector3Scale(Vector3One(), max_extent));
// Root node spans the entire area
const int root = t.create_empty_leaf(min, max);
for (size_t i = 0; i < positions.size(); ++i) {
t.insert(root, static_cast<int>(i), positions[i], MASS, 0);
}
}
auto octree::calculate_force(const int node_idx, const Vector3& pos) const -> Vector3
{
if (node_idx < 0) {