animate.cpp

#include <cstdio>
#include <cmath>
#include <string>
#include "raylib.h"
#include "waterpool.hpp"

const int WIDTH = 160;
const int HEIGHT = 160;
using PoolType = Sapphire::WaterPool<WIDTH, HEIGHT>;

const int PIXELS_PER_CELL = 4;


struct RenderContext
{
    const int screenWidth  = WIDTH * PIXELS_PER_CELL;
    const int screenHeight = HEIGHT * PIXELS_PER_CELL;
    float zoom = 8000.0f;     // pixels per meter
    float xCenter = 0.05f;
    float yCenter = 0.00f;

    int xScreen(float x) const
    {
        return (screenWidth/2) + static_cast<int>(round(zoom * (x - xCenter)));
    }

    int yScreen(float y) const
    {
        return (screenHeight/2) - static_cast<int>(round(zoom * (y - yCenter)));
    }

    int scale(float r) const
    {
        return static_cast<int>(round(zoom * r));
    }

    static Color cellColor(const Sapphire::WaterCell& cell)
    {
        using namespace Sapphire;

        if (cell.wet == 0.0f)
            return WHITE;

        float g = 128.0f * (cell.pos + 1.0f);
        if (g > 255.0f)
            g = 255.0f;
        else if (g < 0.0f)
            g = 0.0f;
        return CLITERAL(Color){0, static_cast<unsigned char>(g), 32, 255};
    }

    void draw(const PoolType& pool)
    {
        using namespace Sapphire;

        for (int i = 0; i < WIDTH; ++i)
        {
            for (int j = 0; j < HEIGHT; ++j)
            {
                const WaterCell& cell = pool.getCell(i, j);
                Color color = cellColor(cell);
                DrawRectangle(i*PIXELS_PER_CELL, j*PIXELS_PER_CELL, PIXELS_PER_CELL, PIXELS_PER_CELL, color);
            }
        }
    }
};


int main(int argc, const char *argv[])
{
    using namespace Sapphire;

    float dt = 1.0f / 48000.0f;
    float halflife = 0.07f;
    float c = 2.0f;             // speed of waves in meters/second
    float s = 0.001f;           // grid spacing in meters
    float k = (c*c) / (s*s);    // propagation constant [second^(-2)]
    PoolType pool;
    RenderContext render;

    for (int i = 0; i < 3; ++i)
    {
        for (int j = 0; j < 3; ++j)
        {
            int r = 1 + i*i + j*j;
            pool.getCell(i + WIDTH/5, j + HEIGHT/2).vel = +20000.0f / r;
        }
    }

    // Create reflective barriers.
    for (int i = 30; i+10 < WIDTH; ++i)
    {
        pool.getCell(i, HEIGHT/2-7).wet = 0.0f;
        pool.getCell(i-13, HEIGHT/2+17).wet = 0.0f;
    }

    InitWindow(render.screenWidth, render.screenHeight, "Water Simulation by Don Cross");
    SetTargetFPS(240);
    while (!WindowShouldClose())
    {
        BeginDrawing();
        ClearBackground(BLACK);
        render.draw(pool);
        EndDrawing();
        pool.update(dt, halflife, k);
    }
    CloseWindow();
    return 0;
}

waterpool.hpp

/*
    waterpool.hpp  -  Don Cross  -  2023-06-26

    Simulation of waves moving on the surface of water.
    Based on ideas from the video
    "How to write a Height-Field Water Simulator with 100 lines of code"
    by Matthias Müller / Ten Minute Physics:
    https://www.youtube.com/watch?v=hswBi5wcqAA
*/
#ifndef __COSINEKITTY_WATERPOOL_HPP
#define __COSINEKITTY_WATERPOOL_HPP

#include <vector>
#include <cmath>

namespace Sapphire
{
    struct WaterCell
    {
        float wet {1.0f};
        float pos {0.0f};
        float vel {0.0f};
        float acc {0.0f};
    };

    template <int WIDTH, int HEIGHT>
    class WaterPool
    {
    private:
        static_assert(WIDTH > 0, "Width must be a positive integer.");
        static_assert(HEIGHT > 0, "Height must be a positive integer.");
        static const int SIZE = WIDTH * HEIGHT;

        std::vector<WaterCell> cell { SIZE };

        static constexpr int index(int i, int j)
        {
            // Use border-wraparound logic.
            // Tolerate -1, but not arbitrarily negative integers.
            return ((i + WIDTH)%WIDTH) + WIDTH*((j + HEIGHT)%HEIGHT);
        }

        float acceleration(const WaterCell& h, int i, int j) const
        {
            const WaterCell& o = cell[index(i, j)];
            return o.wet*(o.pos - h.pos);
        }

    public:
        const WaterCell& getCell(int i, int j) const
        {
            return cell.at(index(i, j));
        }

        WaterCell& getCell(int i, int j)
        {
            return cell.at(index(i, j));
        }

        void update(float dt, float halflife, float k)
        {
            const float damp = pow(0.5, dt/halflife);

            // Calculate acceleration of each water cell.
            for (int i = 0; i < WIDTH; ++i)
            {
                for (int j = 0; j < HEIGHT; ++j)
                {
                    WaterCell& h = cell[index(i, j)];
                    if (h.wet > 0.0f)
                    {
                        h.acc = k * (
                            acceleration(h, i, j+1) +
                            acceleration(h, i, j-1) +
                            acceleration(h, i-1, j) +
                            acceleration(h, i+1, j)
                        );
                    }
                }
            }

            // Use accelerations to update position and velocity of each water cell.
            for (int i = 0; i < WIDTH; ++i)
            {
                for (int j = 0; j < HEIGHT; ++j)
                {
                    WaterCell& h = cell[index(i, j)];
                    if (h.wet > 0.0f)
                    {
                        h.vel = (damp * h.vel) + (dt * h.acc);
                        h.pos += (dt * h.vel);
                    }
                }
            }
        }
    };
}

#endif // __COSINEKITTY_WATERPOOL_HPP

Great work, this follows the video right?

Yes, this is the exact code that was used to create the video at https://www.youtube.com/watch?v=9YV2043cfO0

Where can I find "raylib.h" and "waterpool.hpp"? Sorry for my ignorance if I am missing something trivial.

Where can I find "raylib.h" and "waterpool.hpp"? Sorry for my ignorance if I am missing something trivial.

Hi @satyam-bhardwaj, the file waterpool.hpp is inside this gist. You just need to scroll down below animate.cpp. The file raylib.h is available separately in the raylib project. I hope this helps.

Where can I find "raylib.h" and "waterpool.hpp"? Sorry for my ignorance if I am missing something trivial.

Hi @satyam-bhardwaj, the file waterpool.hpp is inside this gist. You just need to scroll down below animate.cpp. The file raylib.h is available separately in the raylib project. I hope this helps.

Thank you for your kind and quick reply!

How do I compile this?

How do I compile this?

Here is the bash script I used to build and run the program on Linux, using gcc 12.2.0:

#!/bin/bash
g++ -Wall -Werror -O3 -o animate animate.cpp -l raylib -l pthread -l dl || exit 1
./animate $1 || exit 1
exit 0

How do I compile this?

Here is the bash script I used to build and run the program on Linux, using gcc 12.2.0:

#!/bin/bash
g++ -Wall -Werror -O3 -o animate animate.cpp -l raylib -l pthread -l dl || exit 1
./animate $1 || exit 1
exit 0

Oh , thanks a lot
Works 👍
Thanks for making the video , learnt good things ❤️
Excited for more