31.opengl高级光照-泛光bloom

这一章原理并不复杂，涉及到了前面的“帧缓冲”、“HDR”技术，用到了5对shader，绘制的内容相对多一些，整体理解起来多花了点时间。知识点串起来也是个很好的复习。

一、原理

1. 为什么要用泛光？

泛光

bloom技术模拟现实场景中高亮光照效果，通过对光照增加模糊，形成一圈泛光，增强光照的辐射。

2. 泛光的实现

泛光实现流程

• 正常绘制场景
• 输出两路缓冲(1-正常输出；2-高亮部分）
• 第2路高亮缓冲-->高斯模糊
• 两路缓冲叠加，采用HDR输出最终效果

bloom用到了高斯模糊算法

高斯曲线

如果严格按照高斯模糊算法，进行2×32的四方形区域采样，我们必须对每个fragment从一个纹理中采样1024次，计算量偏大。

幸运的是，高斯方程有个非常巧妙的特性，它允许我们把二维方程分解为两个更小的方程：一个描述水平权重，另一个描述垂直权重。我们首先用水平权重在整个纹理上进行水平模糊，然后在经改变的纹理上进行垂直模糊。利用这个特性，结果是一样的，但是可以节省难以置信的性能，因为我们现在只需做32+32次采样，不再是1024了！这叫做两步高斯模糊 两步高斯模糊

两步高斯模糊的效果也不太理想，代码实现中，进行了5次“两步高斯模糊”

3. 代码结构

用到的帧缓冲、shader比较多，先梳理下：

3个帧缓冲，注意，第一个帧缓冲还要绑定一个渲染对象，渲染对象绑定一个深度缓冲，第2、3个帧缓冲处理的是平面数据，不需要深度缓冲： 用到了3个帧缓冲
4组着色器： 4组着色器 按照shader使用顺序理解代码逻辑 渲染流程

二、实现效果

1次两步高斯模糊	5次两步高斯模糊

能明显看到，进行了5次两步高斯模糊后，泛光效果更好

三、完整代码

7.bloom.fs

#version 330 core
layout(location = 0) out vec4 FragColor;
layout(location = 1) out vec4 BrightColor;

in VS_OUT {
    vec3 FragPos;
    vec3 Normal;
    vec2 TexCoords;
} fs_in;

struct Light {
    vec3 Position;
    vec3 Color;
};

uniform Light lights[4];
uniform sampler2D diffuseTexture;
uniform vec3 viewPos;

void main()
{
    vec3 color = texture(diffuseTexture, fs_in.TexCoords).rgb;
    vec3 normal = normalize(fs_in.Normal);
    // ambient
    vec3 ambient = 0.0 * color;
    // lighting
    vec3 lighting = vec3(0.0);
    vec3 viewDir = normalize(viewPos - fs_in.FragPos);
    for (int i = 0; i < 4; i++) {
        vec3 lightDir = normalize(lights[i].Position - fs_in.FragPos);
        float diff = max(dot(lightDir, normal), 0.0);
        vec3 result = lights[i].Color * diff * color;
        //attenuation (use quadratic as we have gama correction)
        float distance = length(fs_in.FragPos - lights[i].Position);
        result *= 1.0/ (distance * distance);
        lighting += result;
    }
    
    vec3 result = ambient + lighting;
    //check whether result is higher than some threshold, if so, output as bloom threshold color
    float brightness = dot(result, vec3(0.2126, 0.7152, 0.0722));
    if (brightness > 1.0)
    {
        BrightColor = vec4(result, 1.0);
    }
    else
    {
        BrightColor = vec4(0.0, 0.0, 0.0, 1.0);
    }
    FragColor = vec4(result, 1.0);
}

7.bloom_final.fs

#version 330 core
layout(location = 0) in vec3 aPos;
layout(location = 1) in vec3 aNormal;
layout(location = 2) in vec2 aTexCoords;

out VS_OUT {
    vec3 FragPos;
    vec3 Normal;
    vec2 TexCoords;
} vs_out;

uniform mat4 projection;
uniform mat4 view;
uniform mat4 model;

void main()
{
    vs_out.FragPos = vec3(model * vec4(aPos, 1.0));
    vs_out.TexCoords = aTexCoords;
    
    mat3 normalMatrix = transpose(inverse(mat3(model)));
    vs_out.Normal = normalize(normalMatrix * aNormal);
    
    gl_Position = projection * view * model * vec4(aPos, 1.0);
}

bloom_final.fs

#version 330 core
out vec4 FragColor;

in vec2 TexCoords;

uniform sampler2D scene;
uniform sampler2D bloomBlur;
uniform bool bloom;
uniform float exposure;

void main(){
    const float gamma = 2.2;
    vec3 hdrColor = texture(scene, TexCoords).rgb;
    vec3 bloomColor = texture(bloomBlur, TexCoords).rgb;
    if (bloom){
        hdrColor += bloomColor; //additive blending
    }
    //tone mapping
    vec3 result = vec3(1.0) - exp(-hdrColor * exposure);
    // also gamma correct while we're at it
    result = pow(result, vec3(1.0 / gamma));
    FragColor = vec4(result, 1.0);
}

7.bloom_final.vs

#version 330 core
layout(location = 0) in vec3 aPos;
layout(location = 1) in vec2 aTexCoords;

out vec2 TexCoords;

void main()
{
    TexCoords = aTexCoords;
    gl_Position = vec4(aPos, 1.0);
}

7.blur.fs

#version 330 core
out vec4 FragColor;

in vec2 TexCoords;

uniform sampler2D image;

uniform bool horizontal;
uniform float weight[5] = float[] (0.2270270270, 0.1945945946, 0.1216216216, 0.0540540541, 0.0162162162);

void main()
{
    vec2 tex_offset = 1.0 / textureSize(image, 0); //get size of sigle texe1
    vec3 result = texture(image, TexCoords).rgb * weight[0];
    if(horizontal)
    {
        for (int i = 1; i < 5; ++i) {
            result += texture(image, TexCoords + vec2(tex_offset.x * i, 0.0)).rgb * weight[i];
            result += texture(image, TexCoords - vec2(tex_offset.x * i, 0.0)).rgb * weight[i];
        }
    }
    else
    {
        for(int i = 1; i < 5; ++i)
        {
            result += texture(image, TexCoords + vec2(0.0, tex_offset.y * i)).rgb * weight[i];
            result += texture(image, TexCoords - vec2(0.0, tex_offset.y * i)).rgb * weight[i];
        }
    }
    FragColor = vec4(result, 1.0);
}

7.blur.vs

#version 330 core
layout(location = 0) in vec3 aPos;
layout(location = 1) in vec2 aTexCoords;

out vec2 TexCoords;

void main()
{
    TexCoords = aTexCoords;
    gl_Position = vec4(aPos, 1.0);
}

7.light_box.fs

#version 330 core
layout(location = 0) out vec4 FragColor;
layout(location = 1) out vec4 BrightColor;

in VS_OUT {
    vec3 FragPos;
    vec3 Normal;
    vec2 TexCoords;
} fs_in;

uniform vec3 lightColor;

void main()
{
    FragColor = vec4(lightColor, 1.0);
    float brightness = dot(FragColor.rgb, vec3(0.2126, 0.7152, 0.0722));
    if(brightness > 1.0)
    {
        BrightColor = vec4(FragColor.rgb, 1.0);
    }
    else{
        BrightColor = vec4(0.0, 0.0, 0.0, 1.0);
    }
}

主程序

#include <glad/glad.h>
#include <GLFW/glfw3.h>
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

#include "Shader.h"
#include "camera.h"
#include "model.h"

#include <iostream>

void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void mouse_callback(GLFWwindow* window, double xpos, double ypos);
void scroll_callback(GLFWwindow* window, double xoffset, double yoffset);
void processInput(GLFWwindow *window);
unsigned int loadTexture(const char *path);
unsigned int loadCubemap(vector<std::string> faces);
void renderScene (const Shader &shader);
void renderCube();
void RenderQuad();

// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;
bool blinn = false;
bool blinnKeyPressed = false;
bool gammaEnabled = true;
bool gammaKeyPressed = false;
bool bloom = true;
bool hdr = true; //change with 'space'
float exposure = 1.0f; // change with Q and E

// camera
Camera camera(glm::vec3(0.0f, 0.0f, 3.0f));
float lastX = (float)SCR_WIDTH / 2.0;
float lastY = (float)SCR_HEIGHT / 2.0;
bool firstMouse = true;

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


int main()
{
    // glfw: initialize and configure
    // ------------------------------
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

#ifdef __APPLE__
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif
    
    // glfw window creation
    // --------------------
    GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "天哥学opengl", NULL, NULL);
    if (window == NULL)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
    glfwSetCursorPosCallback(window, mouse_callback);
    glfwSetScrollCallback(window, scroll_callback);

    // tell GLFW to capture our mouse
//    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);

    // glad: load all OpenGL function pointers
    // ---------------------------------------
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }

//    glPolygonMode(GL_FRONT_AND_BACK ,GL_LINE );
    
    // configure global opengl state
    // -----------------------------
    glEnable(GL_DEPTH_TEST);

    // build and compile shaders
    // -------------------------
    Shader shader("7.bloom.vs", "7.bloom.fs");
    Shader shaderLight("7.bloom.vs", "7.light_box.fs");
    Shader shaderBlur("7.blur.vs", "7.blur.fs");
    Shader shaderBloomFinal("7.bloom_final.vs", "7.bloom_final.fs");
    
    // load textures
    unsigned int woodTexture = loadTexture("resource/wood.png");
    unsigned int containerTexture = loadTexture("resource/container2.png");

    // configure (floating point) framebuffers
    unsigned int hdrFBO;
    glGenFramebuffers(1, &hdrFBO);
    glBindFramebuffer(GL_FRAMEBUFFER, hdrFBO);
    
    // create 2 floating point color buffers (1 for normal rendering, other for brightness treshold values)
    unsigned int colorBuffers[2];
    glGenTextures(2, colorBuffers);
    for (unsigned int i = 0; i < 2; i++) {
        glBindTexture(GL_TEXTURE_2D, colorBuffers[i]);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F, SCR_WIDTH, SCR_HEIGHT, 0, GL_RGBA, GL_FLOAT, NULL);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);  // we clamp to the edge as the blur filter would otherwise sample repeated texture values!
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
        // attach texture to framebuffer
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + i, GL_TEXTURE_2D, colorBuffers[i], 0);
    }
    
    // create and attach depth buffer (renderbuffer)
    unsigned int rboDepth;
    glGenRenderbuffers(1, &rboDepth);
    glBindRenderbuffer(GL_RENDERBUFFER, rboDepth);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, SCR_WIDTH, SCR_HEIGHT);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, rboDepth);
    // tell OpenGL which color attachments we'll use(of this framebuffer) for rendering
    unsigned int attachments[2] = {GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1};
    glDrawBuffers(2, attachments);
    // finally check if framebuffer is complete
    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
    {
        std::cout << "Framebuffer not complete!" << std::endl;
    }
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    
    // ping-pong-framebuffer for blurring
    unsigned int pingpongFBO[2];
    unsigned int pingpongColorbuffers[2];
    glGenFramebuffers(2, pingpongFBO);
    glGenTextures(2, pingpongColorbuffers);
    for (unsigned int i = 0; i < 2; i++) {
        glBindFramebuffer(GL_FRAMEBUFFER, pingpongFBO[i]);
        glBindTexture(GL_TEXTURE_2D, pingpongColorbuffers[i]);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F, SCR_WIDTH, SCR_HEIGHT, 0, GL_RGBA, GL_FLOAT, NULL);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); // we clamp to the edge as the blur filter would otherwise sample repeated texture values!
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, pingpongColorbuffers[i], 0);
        // also check if framebuffers are complete (no need for depth buffer)
        if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
            std::cout << "Framebuffer not complete!" << std::endl;
    }
    
    // lighting info
    // -------------
    // positions
    std::vector<glm::vec3> lightPositions;
    lightPositions.push_back(glm::vec3( 0.0f, 0.5f,  1.5f));
    lightPositions.push_back(glm::vec3(-4.0f, 0.5f, -3.0f));
    lightPositions.push_back(glm::vec3( 3.0f, 0.5f,  1.0f));
    lightPositions.push_back(glm::vec3(-.8f,  2.4f, -1.0f));
    // colors
    std::vector<glm::vec3> lightColors;
    lightColors.push_back(glm::vec3(5.0f,   5.0f,  5.0f));
    lightColors.push_back(glm::vec3(10.0f,  0.0f,  0.0f));
    lightColors.push_back(glm::vec3(0.0f,   0.0f,  15.0f));
    lightColors.push_back(glm::vec3(0.0f,   5.0f,  0.0f));
    
    // shader configuration
    shader.use();
    shader.setInt("diffuseTexture", 0);
    shaderBlur.use();
    shaderBlur.setInt("image", 0);
    shaderBloomFinal.use();
    shaderBloomFinal.setInt("scene", 0);
    shaderBloomFinal.setInt("bloomBlur", 1);
    
    // render loop
    // -----------
    while (!glfwWindowShouldClose(window))
    {
        float currentFrame = glfwGetTime();
        deltaTime = currentFrame - lastFrame;
        lastFrame = currentFrame;
        processInput(window);
    
        glBindFramebuffer(GL_FRAMEBUFFER, hdrFBO);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

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

        shader.use();
        shader.setMat4("projection", projection);
        shader.setMat4("view", view);
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, woodTexture);
        
        // set lighting uniforms
        for (unsigned int i = 0; i < lightPositions.size(); i++) {
            shader.setVec3("lights[" + std::to_string(i) + "].Position", lightPositions[i]);
            shader.setVec3("lights[" + std::to_string(i) + "].Color", lightColors[i]);
        }
        
        shader.setVec3("viewPos", camera.Position);
        
        // create one large cube that acts as the floor
        model = glm::mat4(1.0f);
        model = glm::translate(model, glm::vec3(0.0f, -1.0f, 0.0));
        model = glm::scale(model, glm::vec3(12.5f, 0.5f, 12.5f));
        shader.setMat4("model", model);
        renderCube();
        
        // then create multiple cubes as the scenery
        glBindTexture(GL_TEXTURE_2D, containerTexture);
        model = glm::mat4(1.0f);
        model = glm::translate(model, glm::vec3(0.0f, 1.5f, 0.0));
        model = glm::scale(model, glm::vec3(0.5f));
        shader.setMat4("model", model);
        renderCube();

        model = glm::mat4(1.0f);
        model = glm::translate(model, glm::vec3(2.0f, 0.0f, 1.0));
        model = glm::scale(model, glm::vec3(0.5f));
        shader.setMat4("model", model);
        renderCube();

        model = glm::mat4(1.0f);
        model = glm::translate(model, glm::vec3(-1.0f, -1.0f, 2.0));
        model = glm::rotate(model, glm::radians(60.0f), glm::normalize(glm::vec3(1.0, 0.0, 1.0)));
        shader.setMat4("model", model);
        renderCube();

        model = glm::mat4(1.0f);
        model = glm::translate(model, glm::vec3(0.0f, 2.7f, 4.0));
        model = glm::rotate(model, glm::radians(23.0f), glm::normalize(glm::vec3(1.0, 0.0, 1.0)));
        model = glm::scale(model, glm::vec3(1.25));
        shader.setMat4("model", model);
        renderCube();

        model = glm::mat4(1.0f);
        model = glm::translate(model, glm::vec3(-2.0f, 1.0f, -3.0));
        model = glm::rotate(model, glm::radians(124.0f), glm::normalize(glm::vec3(1.0, 0.0, 1.0)));
        shader.setMat4("model", model);
        renderCube();

        model = glm::mat4(1.0f);
        model = glm::translate(model, glm::vec3(-3.0f, 0.0f, 0.0));
        model = glm::scale(model, glm::vec3(0.5f));
        shader.setMat4("model", model);
        renderCube();
        
        // finally show all the light sources as bright cubes
        shaderLight.use();
        shaderLight.setMat4("projection", projection);
        shaderLight.setMat4("view", view);
        
        for (unsigned int i=0; i < lightPositions.size(); i++) {
            model = glm::mat4(1.0f);
            model = glm::translate(model, glm::vec3(lightPositions[i]));
            model = glm::scale(model, glm::vec3(0.25f));
            shaderLight.setMat4("model", model);
            shaderLight.setVec3("lightColor", lightColors[i]);
            renderCube();
        }
        
        glBindFramebuffer(GL_FRAMEBUFFER, 0);
        
        // 2.blur bright fragments with two-pass Gaussian Blur
        bool horizontal = true, first_iteration = true;
        unsigned int amount = 2;
        shaderBlur.use();
        for (unsigned int i= 0 ; i < amount; i++) {
            glBindFramebuffer(GL_FRAMEBUFFER, pingpongFBO[horizontal]);
            shaderBlur.setInt("horizontal", horizontal);
            glBindTexture(GL_TEXTURE_2D, first_iteration ? colorBuffers[1] : pingpongColorbuffers[!horizontal]);// bind texture of other framebuffer (or scene if first iteration)
            RenderQuad();
            horizontal = !horizontal;
            if (first_iteration) {
                first_iteration = false;
            }
            
        }
        glBindFramebuffer(GL_FRAMEBUFFER, 0);
        
        //3. now render floating point color buffer to 2D quad and tonemap HDR colors to default framebuffer's(clamped) color range
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        shaderBloomFinal.use();
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, colorBuffers[0]);
        glActiveTexture(GL_TEXTURE1);
        glBindTexture(GL_TEXTURE_2D, pingpongColorbuffers[!horizontal]);
        shaderBloomFinal.setInt("bloom", bloom);
        shaderBloomFinal.setFloat("exposure", exposure);
        RenderQuad();
        
//        std::cout << "bloom" << (bloom ? "on" : "off") << " | exposure: " << exposure << std::endl;
        
 
        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        // -------------------------------------------------------------------------------
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    // optional: de-allocate all resources once they've outlived their purpose:
    // ------------------------------------------------------------------------
    glfwTerminate();
    return 0;
}

// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------

bool startRecord = false;

void processInput(GLFWwindow *window)
{
    if (glfwGetKey(window, GLFW_KEY_B) == GLFW_PRESS && !gammaKeyPressed)
    {
        gammaEnabled = !gammaEnabled;
        gammaKeyPressed = true;
    }
    if (glfwGetKey(window, GLFW_KEY_B) == GLFW_RELEASE)
    {
        gammaKeyPressed = false;
    }
    if (glfwGetKey(window, GLFW_KEY_Y))
    {
        std::cout << "Y" << std::endl;
        startRecord = true;
        firstMouse = true;
    }
    
    if (glfwGetKey(window, GLFW_KEY_N))
    {
        std::cout << "N" << std::endl;

        startRecord = false;
    }
    
    if (startRecord) {
        return;
    }
    
    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_Q) == GLFW_PRESS)
        exposure -= 0.5 * deltaTime;
    if (glfwGetKey(window, GLFW_KEY_E) == GLFW_PRESS)
        exposure += 0.5 * deltaTime;
    
    if (glfwGetKey(window, GLFW_KEY_SPACE) == GLFW_PRESS && !gammaKeyPressed)
    {
        hdr = !hdr;
        gammaKeyPressed = true;
    }
    if (glfwGetKey(window, GLFW_KEY_SPACE) == GLFW_RELEASE)
    {
        gammaKeyPressed = false;
    }
}

// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    // make sure the viewport matches the new window dimensions; note that width and
    // height will be significantly larger than specified on retina displays.
    glViewport(0, 0, width, height);
}

// glfw: whenever the mouse moves, this callback is called
// -------------------------------------------------------
void mouse_callback(GLFWwindow* window, double xpos, double ypos)
{
//    std::cout << "xpos : " << xpos << std::endl;
//    std::cout << "ypos : " << ypos << std::endl;
    
    if (startRecord) {
        return;
    }
    
    if (firstMouse)
    {
        lastX = xpos;
        lastY = ypos;
        firstMouse = false;
    }

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

    lastX = xpos;
    lastY = ypos;
    
//    std::cout << "xoffset : " << xoffset << std::endl;
//    std::cout << "yoffset : " << yoffset << std::endl;
    
    camera.ProcessMouseMovement(xoffset, yoffset);
}

// glfw: whenever the mouse scroll wheel scrolls, this callback is called
// ----------------------------------------------------------------------
void scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
{
    camera.ProcessMouseScroll(yoffset);
}

// utility function for loading a 2D texture from file
// ---------------------------------------------------
unsigned int loadTexture(char const * path)
{
    unsigned int textureID;
    glGenTextures(1, &textureID);

    int width, height, nrComponents;
    unsigned char *data = stbi_load(path, &width, &height, &nrComponents, 0);
    if (data)
    {
        GLenum format;
        if (nrComponents == 1)
            format = GL_RED;
        else if (nrComponents == 3)
            format = GL_RGB;
        else if (nrComponents == 4)
            format = GL_RGBA;

        glBindTexture(GL_TEXTURE_2D, textureID);
        glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);
        glGenerateMipmap(GL_TEXTURE_2D);

        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

        stbi_image_free(data);
    }
    else
    {
        std::cout << "Texture failed to load at path: " << path << std::endl;
        stbi_image_free(data);
    }

    return textureID;
}


unsigned int loadCubemap(vector<std::string> faces)
{
    unsigned int textureID;
    glGenTextures(1, &textureID);
    glBindTexture(GL_TEXTURE_CUBE_MAP, textureID);
    
    int width, height, nrChannels;
    for (unsigned int i = 0; i < faces.size(); i++) {
        unsigned char *data = stbi_load(faces[i].c_str(), &width, &height, &nrChannels, 0);

        if (data)
        {
            glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
            stbi_image_free(data);
        }
        else
        {
            std::cout << "Cubemap texture failed to load at path: " << faces[i] << std::endl;
            stbi_image_free(data);
        }
        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
    }
    
    return textureID;
}

void renderScene(const Shader &shader)
{
    // room cube
    glm::mat4 model = glm::mat4(1.0f);
    model = glm::scale(model, glm::vec3(5.0f));
    shader.setMat4("model", model);
    glDisable(GL_CULL_FACE); // note that we disable culling here since we render 'inside' the cube instead of the usual 'outside' which throws off the normal culling methods.
    shader.setInt("reverse_normals", 1); // A small little hack to invert normals when drawing cube from the inside so lighting still works.
    renderCube();
    shader.setInt("reverse_normals", 0); // and of course disable it
    glEnable(GL_CULL_FACE);
    // cubes
    model = glm::mat4(1.0f);
    model = glm::translate(model, glm::vec3(4.0f, -3.5f, 0.0));
    model = glm::scale(model, glm::vec3(0.5f));
    shader.setMat4("model", model);
    renderCube();
    model = glm::mat4(1.0f);
    model = glm::translate(model, glm::vec3(2.0f, 3.0f, 1.0));
    model = glm::scale(model, glm::vec3(0.75f));
    shader.setMat4("model", model);
    renderCube();
    model = glm::mat4(1.0f);
    model = glm::translate(model, glm::vec3(-3.0f, -1.0f, 0.0));
    model = glm::scale(model, glm::vec3(0.5f));
    shader.setMat4("model", model);
    renderCube();
    model = glm::mat4(1.0f);
    model = glm::translate(model, glm::vec3(-1.5f, 1.0f, 1.5));
    model = glm::scale(model, glm::vec3(0.5f));
    shader.setMat4("model", model);
    renderCube();
    model = glm::mat4(1.0f);
    model = glm::translate(model, glm::vec3(-1.5f, 2.0f, -3.0));
    model = glm::rotate(model, glm::radians(60.0f), glm::normalize(glm::vec3(1.0, 0.0, 1.0)));
    model = glm::scale(model, glm::vec3(0.75f));
    shader.setMat4("model", model);
    renderCube();
}


// renderCube() renders a 1x1 3D cube in NDC.
// -------------------------------------------------
unsigned int cubeVAO = 0;
unsigned int cubeVBO = 0;
void renderCube()
{
    // initialize (if necessary)
    if (cubeVAO == 0)
    {
        float vertices[] = {
            // back face
            -1.0f, -1.0f, -1.0f,  0.0f,  0.0f, -1.0f, 0.0f, 0.0f, // bottom-left
             1.0f,  1.0f, -1.0f,  0.0f,  0.0f, -1.0f, 1.0f, 1.0f, // top-right
             1.0f, -1.0f, -1.0f,  0.0f,  0.0f, -1.0f, 1.0f, 0.0f, // bottom-right
             1.0f,  1.0f, -1.0f,  0.0f,  0.0f, -1.0f, 1.0f, 1.0f, // top-right
            -1.0f, -1.0f, -1.0f,  0.0f,  0.0f, -1.0f, 0.0f, 0.0f, // bottom-left
            -1.0f,  1.0f, -1.0f,  0.0f,  0.0f, -1.0f, 0.0f, 1.0f, // top-left
            // front face
            -1.0f, -1.0f,  1.0f,  0.0f,  0.0f,  1.0f, 0.0f, 0.0f, // bottom-left
             1.0f, -1.0f,  1.0f,  0.0f,  0.0f,  1.0f, 1.0f, 0.0f, // bottom-right
             1.0f,  1.0f,  1.0f,  0.0f,  0.0f,  1.0f, 1.0f, 1.0f, // top-right
             1.0f,  1.0f,  1.0f,  0.0f,  0.0f,  1.0f, 1.0f, 1.0f, // top-right
            -1.0f,  1.0f,  1.0f,  0.0f,  0.0f,  1.0f, 0.0f, 1.0f, // top-left
            -1.0f, -1.0f,  1.0f,  0.0f,  0.0f,  1.0f, 0.0f, 0.0f, // bottom-left
            // left face
            -1.0f,  1.0f,  1.0f, -1.0f,  0.0f,  0.0f, 1.0f, 0.0f, // top-right
            -1.0f,  1.0f, -1.0f, -1.0f,  0.0f,  0.0f, 1.0f, 1.0f, // top-left
            -1.0f, -1.0f, -1.0f, -1.0f,  0.0f,  0.0f, 0.0f, 1.0f, // bottom-left
            -1.0f, -1.0f, -1.0f, -1.0f,  0.0f,  0.0f, 0.0f, 1.0f, // bottom-left
            -1.0f, -1.0f,  1.0f, -1.0f,  0.0f,  0.0f, 0.0f, 0.0f, // bottom-right
            -1.0f,  1.0f,  1.0f, -1.0f,  0.0f,  0.0f, 1.0f, 0.0f, // top-right
            // right face
             1.0f,  1.0f,  1.0f,  1.0f,  0.0f,  0.0f, 1.0f, 0.0f, // top-left
             1.0f, -1.0f, -1.0f,  1.0f,  0.0f,  0.0f, 0.0f, 1.0f, // bottom-right
             1.0f,  1.0f, -1.0f,  1.0f,  0.0f,  0.0f, 1.0f, 1.0f, // top-right
             1.0f, -1.0f, -1.0f,  1.0f,  0.0f,  0.0f, 0.0f, 1.0f, // bottom-right
             1.0f,  1.0f,  1.0f,  1.0f,  0.0f,  0.0f, 1.0f, 0.0f, // top-left
             1.0f, -1.0f,  1.0f,  1.0f,  0.0f,  0.0f, 0.0f, 0.0f, // bottom-left
            // bottom face
            -1.0f, -1.0f, -1.0f,  0.0f, -1.0f,  0.0f, 0.0f, 1.0f, // top-right
             1.0f, -1.0f, -1.0f,  0.0f, -1.0f,  0.0f, 1.0f, 1.0f, // top-left
             1.0f, -1.0f,  1.0f,  0.0f, -1.0f,  0.0f, 1.0f, 0.0f, // bottom-left
             1.0f, -1.0f,  1.0f,  0.0f, -1.0f,  0.0f, 1.0f, 0.0f, // bottom-left
            -1.0f, -1.0f,  1.0f,  0.0f, -1.0f,  0.0f, 0.0f, 0.0f, // bottom-right
            -1.0f, -1.0f, -1.0f,  0.0f, -1.0f,  0.0f, 0.0f, 1.0f, // top-right
            // top face
            -1.0f,  1.0f, -1.0f,  0.0f,  1.0f,  0.0f, 0.0f, 1.0f, // top-left
             1.0f,  1.0f , 1.0f,  0.0f,  1.0f,  0.0f, 1.0f, 0.0f, // bottom-right
             1.0f,  1.0f, -1.0f,  0.0f,  1.0f,  0.0f, 1.0f, 1.0f, // top-right
             1.0f,  1.0f,  1.0f,  0.0f,  1.0f,  0.0f, 1.0f, 0.0f, // bottom-right
            -1.0f,  1.0f, -1.0f,  0.0f,  1.0f,  0.0f, 0.0f, 1.0f, // top-left
            -1.0f,  1.0f,  1.0f,  0.0f,  1.0f,  0.0f, 0.0f, 0.0f  // bottom-left
        };
        glGenVertexArrays(1, &cubeVAO);
        glGenBuffers(1, &cubeVBO);
        // fill buffer
        glBindBuffer(GL_ARRAY_BUFFER, cubeVBO);
        glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
        // link vertex attributes
        glBindVertexArray(cubeVAO);
        glEnableVertexAttribArray(0);
        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
        glEnableVertexAttribArray(1);
        glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
        glEnableVertexAttribArray(2);
        glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
        glBindBuffer(GL_ARRAY_BUFFER, 0);
        glBindVertexArray(0);
    }
    // render Cube
    glBindVertexArray(cubeVAO);
    glDrawArrays(GL_TRIANGLES, 0, 36);
    glBindVertexArray(0);
}

// RenderQuad() Renders a 1x1 quad in NDC
unsigned int quadVAO = 0;
unsigned int quadVBO;

void RenderQuad()
{
      if (quadVAO == 0)
    {
        GLfloat quadVertices[] = {
            // Positions        // Texture Coords
            -1.0f, 1.0f, 0.0f, 0.0f, 1.0f,
            -1.0f, -1.0f, 0.0f, 0.0f, 0.0f,
            1.0f, 1.0f, 0.0f, 1.0f, 1.0f,
            1.0f, -1.0f, 0.0f, 1.0f, 0.0f,
        };
        // Setup plane VAO
        glGenVertexArrays(1, &quadVAO);
        glGenBuffers(1, &quadVBO);
        glBindVertexArray(quadVAO);
        glBindBuffer(GL_ARRAY_BUFFER, quadVBO);
        glBufferData(GL_ARRAY_BUFFER, sizeof(quadVertices), &quadVertices, GL_STATIC_DRAW);
        glEnableVertexAttribArray(0);
        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)0);
        glEnableVertexAttribArray(1);
        glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
    }
    glBindVertexArray(quadVAO);
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
    glBindVertexArray(0);
}