From b84c5f141eefd1d116b2eab5682d10c221a4fbf6 Mon Sep 17 00:00:00 2001
From: Yggdrasil75 <cblackburn7557@gmail.com>
Date: Tue, 3 Feb 2026 14:32:37 -0500
Subject: [PATCH] gonna work on this more later. adding a fluid sim, gonna use
 it to create the planet by spawning in heavy particles and then slowly
 lighter and smaller over time until a sphere is formed.

---
 util/sim/fluidsim.cpp | 83 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 util/sim/fluidsim.cpp

diff --git a/util/sim/fluidsim.cpp b/util/sim/fluidsim.cpp
new file mode 100644
index 0000000..d016746
--- /dev/null
+++ b/util/sim/fluidsim.cpp
@@ -0,0 +1,83 @@
+#include <map>
+#include <iostream>
+#include <vector>
+#include <chrono>
+#include <thread>
+#include <atomic>
+#include <mutex>
+#include <cmath>
+#include <random>
+#include <algorithm>
+
+#include "../util/grid/grid3eigen.hpp"
+#include "../util/output/bmpwriter.hpp"
+#include "../util/output/frame.hpp"
+#include "../util/timing_decorator.cpp"
+#include "../util/noise/pnoise2.hpp"
+#include "../util/noise/pnoise.cpp"
+#include "../util/output/aviwriter.hpp"
+
+#include "../imgui/imgui.h"
+#include "../imgui/backends/imgui_impl_glfw.h"
+#include "../imgui/backends/imgui_impl_opengl3.h"
+#include <GLFW/glfw3.h>
+#include "../stb/stb_image.h"
+
+
+struct fluidParticle {
+    Eigen::Matrix<float, 3, 1> pos;
+    Eigen::Matrix<float, 3, 1> velocity;
+    Eigen::Matrix<float, 3, 1> acceleration;
+    Eigen::Matrix<float, 3, 1> forceAccumulator;
+    float pressure;
+    float viscosity;
+    float restitution;
+    float mass;
+};
+
+struct gridDefaults {
+    float gridSizeCube = 1024;
+};
+
+Eigen::Matrix<float, 3, 1> posGen() {
+    static std::random_device rd;
+    static std::mt19937 gen(rd());
+    static std::normal_distribution<float> dist(0.0f, 1024.0f);
+    
+    return Eigen::Matrix<float, 3, 1>(
+        dist(gen),
+        dist(gen),
+        dist(gen)
+    );
+}
+class fluidSim {
+    std::unordered_map<size_t, Eigen::Matrix<float, 3, 1>> idposMap;
+    Octree<fluidParticle> grid;
+    
+    void spawnParticles(fluidParticle toSpawn, int count) {
+        for (int i = 0; i < count; i++) {
+            Eigen::Matrix<float, 3, 1> pos = posGen();
+            grid.set(toSpawn, pos, true, {toSpawn.mass / 1000, toSpawn.mass / 1000, toSpawn.mass / 1000}, 1, true, 1, false);
+            
+        }
+    }
+
+    void applyPhysics() {
+        for (auto& meh : idposMap) {
+            std::shared_ptr<Octree<fluidParticle>::NodeData> mehdata = grid.find(meh.second);
+            std::vector<std::shared_ptr<Octree<fluidParticle>::NodeData>> neighbors = grid.findInRadius(meh.second, mehdata->data.mass);
+            ///TODO: 
+            // apply velocity to have particle move
+            // use mass of neighboring particles to change direction towards them
+            // ressure pushes particles away if they are too close
+            // resitution controls how much pressure builds up based on how close particles are
+            // have to find a way to have a clump use their combined mass instead of individual mass.
+            //if a particle leaves the grid, destroy it and spawn a new one
+
+            for (auto& neighbor : neighbors) {
+
+                
+            }
+        }
+    }
+};
\ No newline at end of file