main.cpp

#include <glad/glad.h>
#include <GLFW/glfw3.h>

#include "Shader.h"
#include "Camera.h"
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"
#include "Fluid.h"

#include <iostream>

void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void cursor_pos_callback(GLFWwindow* window, double xpos, double ypos);
void scroll_callback(GLFWwindow* window, double xoffset, double yoffset);
void processInput(GLFWwindow* window);
void mouse_button_callback(GLFWwindow* window, int button, int action, int mods);

// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

// camera
Camera camera(glm::vec3(0.0f, 0.0f, 9.0f));
float clastX = SCR_WIDTH / 2.0f;
float clastY = SCR_HEIGHT / 2.0f;
bool cameraFirstMouse = true;
bool cameraCanRotate = false;

// fluid
Fluid* fluid;

// timing
float deltaTime = 0.0f;
float totalTime = 0.0f;
float lastFrame = 0.0f;

int main()
{
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "FluidSimulation", NULL, NULL);
    if (window == NULL)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
    glfwSetMouseButtonCallback(window, mouse_button_callback);
    glfwSetCursorPosCallback(window, cursor_pos_callback);
    glfwSetScrollCallback(window, scroll_callback);

    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }

    // 开启更新深度缓冲区的功能
    glEnable(GL_DEPTH_TEST);

    Shader fluid_shader("fluid.vert", "fluid.frag");

    // 初始化流体质点
    const int side = 24;
    float* draw_ptr = new float[side * side * side * 3];
    fluid = new Fluid(side, draw_ptr);

    // 绘制流体点
    unsigned int VAO, VBO;
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);

    glBindVertexArray(VAO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, side * side * side * 3 * sizeof(float), draw_ptr, GL_DYNAMIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), 0);
    glEnableVertexAttribArray(0);

    // render loop
    // -----------
    while (!glfwWindowShouldClose(window))
    {
        float currentFrame = glfwGetTime();
        deltaTime = currentFrame - lastFrame;
        lastFrame = currentFrame;
        
        // 移动并更新 GPU 中的数据
        if ((totalTime += deltaTime) > 0.02f) {
            fluid->onUpdate(totalTime);
            totalTime = 0.0f;
            glBindBuffer(GL_ARRAY_BUFFER, VBO);
            glBufferSubData(GL_ARRAY_BUFFER, 0, side * side * side * 3 * sizeof(float), draw_ptr);
        }

        processInput(window);

        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        // view/projection transformations
        glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);
        glm::mat4 view = camera.GetViewMatrix();

        // render container
        fluid_shader.use();
        fluid_shader.setMat4("projection", projection);
        fluid_shader.setMat4("view", view);

        glBindVertexArray(VAO);
        glBindBuffer(GL_ARRAY_BUFFER, VBO);
        glDrawArrays(GL_POINTS, 0, side * side * side);

        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        // -------------------------------------------------------------------------------
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    // 释放资源
    glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);

    delete fluid;
    delete[] draw_ptr;

    // glfw: terminate, clearing all previously allocated GLFW resources.
    // ------------------------------------------------------------------
    glfwTerminate();
    return 0;
}

void processInput(GLFWwindow* window)
{
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS) glfwSetWindowShouldClose(window, true);

    if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS) camera.ProcessKeyboard(FORWARD, deltaTime);
    if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS) camera.ProcessKeyboard(BACKWARD, deltaTime);
    if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS) camera.ProcessKeyboard(LEFT, deltaTime);
    if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS) camera.ProcessKeyboard(RIGHT, deltaTime);

    if (glfwGetKey(window, GLFW_KEY_SPACE) == GLFW_PRESS) fluid->reset();
}

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    glViewport(0, 0, width, height);
}

void cursor_pos_callback(GLFWwindow* window, double xpos, double ypos)
{
    if (cameraCanRotate) {
        if (cameraFirstMouse)
        {
            clastX = xpos;
            clastY = ypos;
            cameraFirstMouse = false;
        }

        float xoffset = xpos - clastX;
        float yoffset = clastY - ypos; // reversed since y-coordinates go from bottom to top

        clastX = xpos;
        clastY = ypos;

        camera.ProcessMouseMovement(xoffset, yoffset);
    }
}

void scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
{
    camera.ProcessMouseScroll(yoffset);
}

void mouse_button_callback(GLFWwindow* window, int button, int action, int mods)
{
    if (action == GLFW_PRESS) {
        if (button == GLFW_MOUSE_BUTTON_RIGHT) cameraCanRotate = true;
    } else if (action == GLFW_RELEASE) {
        if (button == GLFW_MOUSE_BUTTON_RIGHT) {
            cameraCanRotate = false;
            cameraFirstMouse = true;
        }
    }
    return;
}