Initial

.idea/.gitignore

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+# Default ignored files
+/shelf/
+/workspace.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.30)
+project(VoxelSim)
+
+set(CMAKE_CXX_STANDARD 23)
+
+add_executable(VoxelSim main.cpp
+        simulation.cpp
+        simulation.h)

main.cpp

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+#include <iostream>
+#include <cstring>
+#include "simulation.h"
+
+void printGrid(simulation::SimulationGrid* grid)
+{
+    std::cout << std::string(grid->x_max+2, '_') << std::endl;
+    for (unsigned char y = grid->y_max; y > 0; y--)
+    {
+        std::cout << "|";
+        for (unsigned char x = 0; x < grid->x_max; x++)
+        {
+            unsigned int offset = simulation::getCellOffset(x, y-1, 0, grid);
+            unsigned int material = grid->cells[offset];
+            switch (material)
+            {
+            case simulation::VACUUM:
+                std::cout << " ";
+                break;
+            case simulation::WATER:
+                std::cout << "~";
+                break;
+            default:
+                std::cout << "?";
+            }
+        }
+        std::cout << "|" << std::endl;
+    }
+    std::cout << std::string(grid->x_max+2, '_') << std::endl;
+}
+
+int main()
+{
+    unsigned char xMax = 50;
+    unsigned char yMax = 20;
+    unsigned char zMax = 1;
+    size_t bufferSizeInBytes = sizeof(unsigned int) * xMax * yMax * zMax;
+    auto inCells = static_cast<unsigned int*>(std::malloc(bufferSizeInBytes));
+    std::memset(inCells, 0, bufferSizeInBytes);
+    auto outCells = static_cast<unsigned int*>(std::malloc(bufferSizeInBytes));
+    simulation::SimulationGrid inGrid = {
+        inCells, xMax, yMax, zMax
+    };
+    simulation::SimulationGrid outGrid = {
+        outCells, xMax, yMax, zMax
+    };
+
+    step(0, &inGrid, &outGrid);
+
+    printGrid(&outGrid);
+    std::free(inCells);
+    std::free(outCells);
+    return 0;
+}

simulation.cpp

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+#include "simulation.h"
+
+namespace simulation
+{
+    unsigned int getCellOffset(
+        unsigned char x,
+        unsigned char y,
+        unsigned char z,
+        SimulationGrid* grid)
+    {
+        if (x < grid->x_max && y < grid->y_max && z < grid->z_max)
+        {
+            unsigned int offset = x + y * grid->x_max + z * (grid->y_max * grid->x_max);
+            return offset;
+        }
+        return -1;
+    }
+
+    void step(
+        double millisecondsSinceLastStep,
+        SimulationGrid* input,
+        SimulationGrid* output)
+    {
+        for (unsigned char x = 0; x < input->x_max; x++)
+        {
+            for (unsigned char y = 0; y < input->y_max; y++)
+            {
+                for (unsigned char z = 0; z < input->z_max; z++)
+                {
+                    unsigned int offset = getCellOffset(x, y, z, input);
+                    unsigned int material = input->cells[offset];
+                    switch (material)
+                    {
+                    case WATER:
+                        if (y > 0)
+                        {
+                            unsigned int downOffset = getCellOffset(x, y - 1, z, input);
+                            // Flow down if cell is empty
+                            if (output->cells[downOffset] == 0)
+                            {
+                                output->cells[downOffset] = material;
+                            }
+                        }
+                    default:
+                        output->cells[offset] = material;
+                    }
+                }
+            }
+        }
+    }
+}

simulation.h

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+//
+// Created by johan on 2025-01-25.
+//
+
+#ifndef SIMULATION_H
+#define SIMULATION_H
+namespace simulation
+{
+    enum Fluid
+    {
+        VACUUM = 0,
+        WATER,
+        MERCURY
+    };
+
+    struct SimulationGrid
+    {
+        unsigned int* cells;
+        unsigned char x_max;
+        unsigned char y_max;
+        unsigned char z_max;
+    };
+
+    void step(
+        double millisecondsSinceLastStep,
+        SimulationGrid* input,
+        SimulationGrid* output);
+
+    unsigned int getCellOffset(
+        unsigned char x,
+        unsigned char y,
+        unsigned char z,
+        SimulationGrid* grid);
+
+}
+
+#endif //SIMULATION_H