38.opengl-字体渲染

一、文本渲染原理

1.1经典文本渲染:位图字体

早期的文本渲染,是将需要的字符集放到一个大纹理中,这个纹理称为“位图字体”,渲染某个字符时,通过查找坐标,找到该字符对应的区域并渲染出来,再启动混合,让字符纹理的背景保持透明,非常容易理解。

这种方式的缺点也比较明显: 1)字符集非常小,不支持拓展,因为已经生成了字符表); 2)已经预光栅化了,所以分辨率已经固化了,修改分辨率需要重新编译一张字符纹理表(“纹理表”是笔者自创的称呼)

1.2 现代文本渲染

上面的图很清楚的说明了一个字符的定义规则,注意,有些字符在基准线之上,有少数字符在基准线之下,比如g p j等。 关于字符更详细的定义,参考:https://www.supremo.co.uk/typeterms/

基于经典文本渲染的瓶颈,现在有更好的文本渲染方式,基于FreeType处理。 FreeType有以下优点: 1)跨平台 2)能加载TrueType字体,TrueType不是基于像素定义的,而是通过数学公式(曲线)来定义,类似矢量图像,所以方便渲染不同大小的字形,有更好的适配能力

二、基于freetype渲染文本

文本渲染

文本轮廓

关闭混合,可以看到每个字符占的区域大小是不一样的

2.1 先看看着shader的实现

顶点着色器:很简单,有个小技巧,一个vec4 xy存字符position,zw存纹理,节省内存

#version 330 core
layout (location = 0) in vec4 vertex;
out vec2 TexCoords;

uniform mat4 projection;

void main ()
{
    gl_Position = projection * vec4(vertex.xy, 0.0, 1.0); // z坐标=0,在原点,w坐标为1,无缩放
    TexCoords = vertex.zw;
}

片段着色器: sampled取出r值,字形原始数据没有颜色,r通道存放的是alpha值,r值与设置的color做混合,即可得到带颜色的文字。

注意下面代码中注释的部分,如果不开启混合,需要判断alpha通道的值为0时,进行discard操作,否则按照当前的逻辑字符会渲染成一个矩形图案。开启混合模式,当前窗口的颜色缓冲会把字符的背景中镂空的部分覆盖掉

#version 330 core
in vec2 TexCoords;
out vec4 color;

uniform sampler2D text;
uniform vec3 textColor;

void main()
{
    vec4 sampled = vec4(1.0, 1.0, 1.0, texture(text, TexCoords).r);
   // if (sampled.w == 0) {
   //     discard;
   // }
    color = vec4(textColor, 1.0) * sampled;
}
2.1 工程中引入需要的头文件
#include <ft2build.h>
#include FT_FREETYPE_H  
2.2 启用混合模式,某则渲染出来是方形图案(不启用混合,通过其他方式也可以实现)
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
2.3 freetype库初始化
 // FreeType
    FT_Library ft;
    // All functions return a value different than 0 whenever an error occurred
    if (FT_Init_FreeType(&ft)) {
        std::cout << "ERROR::freetype: Could not init FreeType Library" << std::endl;
    }
    // Load font as face
    FT_Face face;
    if (FT_New_Face(ft, "fonts/Antonio-Bold.ttf", 0, &face)) {
        std::cout << "ERROR::FREETYPE: Failed to load font" << std::endl;
    }
    FT_Set_Pixel_Sizes(face, 0, 48);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
2.4 加载128个常用字符(降低使用难度),存放到map中,使用完记得释放freetype
    for (GLubyte c = 0; c < 128; c++) {
        // Load character glyph
        if (FT_Load_Char(face, c, FT_LOAD_RENDER))
        {
            std::cout << "ERROR::FREETYPE: Failed to load Glyph" << std::endl;
            continue;
        }
        
        // Generate texture
        GLuint texture;
        glGenTextures(1, &texture);
        glBindTexture(GL_TEXTURE_2D, texture);
        glTexImage2D(
                     GL_TEXTURE_2D,
                     0,
                     GL_RED,
                     face->glyph->bitmap.width,
                     face->glyph->bitmap.rows,
                     0,
                     GL_RED,
                     GL_UNSIGNED_BYTE,
                     face->glyph->bitmap.buffer);
        
        // Set texture options
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

        // Now store character for later use
        Character character = {
            texture,
            glm::ivec2(face->glyph->bitmap.width, face->glyph->bitmap.rows),
            glm::ivec2(face->glyph->bitmap_left, face->glyph->bitmap_top),
            static_cast<GLuint>(face->glyph->advance.x)
        };
        Characters.insert(std::pair<GLchar, Character>(c, character));
    }
    // Destroy FreeType once we're finished
    FT_Done_Face(face);
    FT_Done_FreeType(ft);
2.5 render loop中渲染两端测试文字

注意,这里渲染文字使用正交矩阵,没有像之前使用投影矩阵,并且投影矩阵的左下角是(0, 0)坐标

glm::mat4 projection = glm::ortho(0.0f, static_cast<GLfloat>(SCR_WIDTH), 0.0f, static_cast<GLfloat>(SCR_HEIGHT));
RenderText(shader, "This is sample text", 25.0f, 25.0f, 1.0f, glm::vec3(0.5f, 0.8f, 0.2f));
RenderText(shader, "(C) LearnOpenGL.com", 540.0f, 570.0f, 0.5f, glm::vec3(0.3f, 0.7f, 0.9f));

RenderText的逻辑不复杂,直接看代码理解即可

void RenderText(Shader &shader, std::string text, GLfloat x, GLfloat y, GLfloat scale, glm::vec3 color)
{
    shader.use();
    shader.setVec3("textColor", color.x, color.y, color.z);
    glActiveTexture(GL_TEXTURE0);
    glBindVertexArray(VAO);
    
    std::string::const_iterator c;
    for (c = text.begin(); c != text.end(); c++) {
        Character ch = Characters[*c];
        
        GLfloat xpos = x + ch.Bearing.x * scale;
        GLfloat ypos = y - (ch.Size.y - ch.Bearing.y) * scale;
        
        GLfloat w = ch.Size.x * scale;
        GLfloat h = ch.Size.y * scale;
        
        // Update VBO for each character
        GLfloat vertices[6][4] = {
            {xpos,      ypos + h, 0.0, 0.0},
            {xpos,      ypos,     0.0, 1.0},
            {xpos + w,  ypos,     1.0, 1.0},
            {xpos,      ypos + h, 0.0, 0.0},
            {xpos + w,  ypos,     1.0, 1.0},
            {xpos + w,  ypos + h, 1.0, 0.0},
        };
        // Render glyph texture over quad
        glBindTexture(GL_TEXTURE_2D, ch.TextureID);
        // Update content of VBO memory
        glBindBuffer(GL_ARRAY_BUFFER, VBO);
        glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices);
        
        glBindBuffer(GL_ARRAY_BUFFER, 0);
        //Render quad
        glDrawArrays(GL_TRIANGLES, 0, 6);
        // Now advance cursors for next glyph (note that advance is number of 1/64 pixels)
        x += (ch.Advance >> 6) * scale;
    }
    glBindVertexArray(0);
    glBindTexture(GL_TEXTURE_2D, 0);
}

三、补充:mac freetype安装配置,不复杂,简单说明

如果是Android/iOS,需通过freetype源码编译对应的平台库,前端直接引用freetype.js更方便

1. brew install freetype

安装完成会在local/include/freetype2/下生成头文件

因为freetype的代码依赖结构,需要修改header文件,讲freetype2目录下的头文件copy到include下,否则会编译报错

2. Xcode环境变量配置

2.1 xcode->preference->locations->custom paths

2.2 Search Paths 增加Header和 Library

2.3 Build Phases 增加库依赖

四、完整代码

#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>
#include <random>
#include <ft2build.h>
#include FT_FREETYPE_H

// Holds all state information relevant to a character as loaded using FreeType
struct Character {
    GLuint TextureID; // ID handle of the glyph texture
    glm::ivec2 Size;
    glm::ivec2 Bearing; // bearing 这里翻译成方位/方向
    GLuint Advance;
};

std::map<GLchar, Character> Characters;
GLuint VAO, VBO;

void RenderText(Shader &shader, std::string text, GLfloat x, GLfloat y, GLfloat scale, glm::vec3 color);

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();
void renderSphere();

// 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;

unsigned int draw_mode = 1;

float lerp(float a, float b, float f)
{
    return a + f * (b - a);
}

int main()
{
    // glfw: initialize and configure
    // ------------------------------
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
//    glfwWindowHint(GLFW_SAMPLES, 4);

    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;
    }
    glViewport(0, 0, SCR_WIDTH, SCR_HEIGHT);
//    glPolygonMode(GL_FRONT_AND_BACK ,GL_LINE );
    glEnable(GL_CULL_FACE);
//    glEnable(GL_BLEND);
//    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    // build and compile shaders
    
    Shader shader("text.vs", "text.fs");
    glm::mat4 projection = glm::ortho(0.0f, static_cast<GLfloat>(SCR_WIDTH), 0.0f, static_cast<GLfloat>(SCR_HEIGHT));
    shader.use();
    shader.setMat4("projection", projection);
    
    // FreeType
    FT_Library ft;
    // All functions return a value different than 0 whenever an error occurred
    if (FT_Init_FreeType(&ft)) {
        std::cout << "ERROR::freetype: Could not init FreeType Library" << std::endl;
    }
    
    // Load font as face
    FT_Face face;
    if (FT_New_Face(ft, "fonts/Antonio-Bold.ttf", 0, &face)) {
        std::cout << "ERROR::FREETYPE: Failed to load font" << std::endl;
    }
    
    FT_Set_Pixel_Sizes(face, 0, 48);
    
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    
    for (GLubyte c = 0; c < 128; c++) {
        // Load character glyph
        if (FT_Load_Char(face, c, FT_LOAD_RENDER))
        {
            std::cout << "ERROR::FREETYPE: Failed to load Glyph" << std::endl;
            continue;
        }
        
        // Generate texture
        GLuint texture;
        glGenTextures(1, &texture);
        glBindTexture(GL_TEXTURE_2D, texture);
        glTexImage2D(
                     GL_TEXTURE_2D,
                     0,
                     GL_RED,
                     face->glyph->bitmap.width,
                     face->glyph->bitmap.rows,
                     0,
                     GL_RED,
                     GL_UNSIGNED_BYTE,
                     face->glyph->bitmap.buffer);
        
        // Set texture options
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

        // Now store character for later use
        Character character = {
            texture,
            glm::ivec2(face->glyph->bitmap.width, face->glyph->bitmap.rows),
            glm::ivec2(face->glyph->bitmap_left, face->glyph->bitmap_top),
            static_cast<GLuint>(face->glyph->advance.x)
        };
        Characters.insert(std::pair<GLchar, Character>(c, character));
    }
    
    glBindTexture(GL_TEXTURE_2D, 0);
    // Destroy FreeType once we're finished
    FT_Done_Face(face);
    FT_Done_FreeType(ft);

    // Confiture VAO/VBO for texture quads
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);
    glBindVertexArray(VAO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 6 * 4, NULL, GL_DYNAMIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), 0);
    glBindVertexArray(0);
    glBindVertexArray(0);
    
    // render loop
    // -----------
    while (!glfwWindowShouldClose(window))
    {
        // per-frame time logic
        float currentFrame = glfwGetTime();
        deltaTime = currentFrame - lastFrame;
        lastFrame = currentFrame;

        processInput(window);
        
        //render
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);
        
        RenderText(shader, "This is sample text", 25.0f, 25.0f, 1.0f, glm::vec3(0.5f, 0.8f, 0.2f));
        RenderText(shader, "(C) LearnOpenGL.com", 540.0f, 570.0f, 0.5f, glm::vec3(0.3f, 0.7f, 0.9f));

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

void RenderText(Shader &shader, std::string text, GLfloat x, GLfloat y, GLfloat scale, glm::vec3 color)
{
    shader.use();
    shader.setVec3("textColor", color.x, color.y, color.z);
    glActiveTexture(GL_TEXTURE0);
    glBindVertexArray(VAO);
    
    std::string::const_iterator c;
    for (c = text.begin(); c != text.end(); c++) {
        Character ch = Characters[*c];
        
        GLfloat xpos = x + ch.Bearing.x * scale;
        GLfloat ypos = y - (ch.Size.y - ch.Bearing.y) * scale;
        
        GLfloat w = ch.Size.x * scale;
        GLfloat h = ch.Size.y * scale;
        
        // Update VBO for each character
        GLfloat vertices[6][4] = {
            {xpos,      ypos + h, 0.0, 0.0},
            {xpos,      ypos,     0.0, 1.0},
            {xpos + w,  ypos,     1.0, 1.0},
            {xpos,      ypos + h, 0.0, 0.0},
            {xpos + w,  ypos,     1.0, 1.0},
            {xpos + w,  ypos + h, 1.0, 0.0},
        };
        // Render glyph texture over quad
        glBindTexture(GL_TEXTURE_2D, ch.TextureID);
        // Update content of VBO memory
        glBindBuffer(GL_ARRAY_BUFFER, VBO);
        glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices);
        
        glBindBuffer(GL_ARRAY_BUFFER, 0);
        //Render quad
        glDrawArrays(GL_TRIANGLES, 0, 6);
        // Now advance cursors for next glyph (note that advance is number of 1/64 pixels)
        x += (ch.Advance >> 6) * scale;
    }
    glBindVertexArray(0);
    glBindTexture(GL_TEXTURE_2D, 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_1) == GLFW_PRESS) {
        draw_mode = 1;
    }
    if (glfwGetKey(window, GLFW_KEY_2) == GLFW_PRESS) {
        draw_mode = 2;
    }
    if (glfwGetKey(window, GLFW_KEY_3) == GLFW_PRESS) {
        draw_mode = 3;
    }
    if (glfwGetKey(window, GLFW_KEY_4) == GLFW_PRESS) {
        draw_mode = 4;
    }
    
    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);
    }
    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);
}

unsigned int sphereVAO = 0;
unsigned int indexCount;
void renderSphere()
{
    if (sphereVAO == 0)
    {
        glGenVertexArrays(1, &sphereVAO);

        unsigned int vbo, ebo;
        glGenBuffers(1, &vbo);
        glGenBuffers(1, &ebo);

        std::vector<glm::vec3> positions;
        std::vector<glm::vec2> uv;
        std::vector<glm::vec3> normals;
        std::vector<unsigned int> indices;

        const unsigned int X_SEGMENTS = 64;
        const unsigned int Y_SEGMENTS = 64;
        const float PI = 3.14159265359;
        for (unsigned int y = 0; y <= Y_SEGMENTS; ++y)
        {
            for (unsigned int x = 0; x <= X_SEGMENTS; ++x)
            {
                float xSegment = (float)x / (float)X_SEGMENTS;
                float ySegment = (float)y / (float)Y_SEGMENTS;
                float xPos = std::cos(xSegment * 2.0f * PI) * std::sin(ySegment * PI);
                float yPos = std::cos(ySegment * PI);
                float zPos = std::sin(xSegment * 2.0f * PI) * std::sin(ySegment * PI);

                positions.push_back(glm::vec3(xPos, yPos, zPos));
                uv.push_back(glm::vec2(xSegment, ySegment));
                normals.push_back(glm::vec3(xPos, yPos, zPos));
            }
        }

        bool oddRow = false;
        for (unsigned int y = 0; y < Y_SEGMENTS; ++y)
        {
            if (!oddRow) // even rows: y == 0, y == 2; and so on
            {
                for (unsigned int x = 0; x <= X_SEGMENTS; ++x)
                {
                    indices.push_back(y       * (X_SEGMENTS + 1) + x);
                    indices.push_back((y + 1) * (X_SEGMENTS + 1) + x);
                }
            }
            else
            {
                for (int x = X_SEGMENTS; x >= 0; --x)
                {
                    indices.push_back((y + 1) * (X_SEGMENTS + 1) + x);
                    indices.push_back(y       * (X_SEGMENTS + 1) + x);
                }
            }
            oddRow = !oddRow;
        }
        indexCount = indices.size();

        std::vector<float> data;
        for (unsigned int i = 0; i < positions.size(); ++i)
        {
            data.push_back(positions[i].x);
            data.push_back(positions[i].y);
            data.push_back(positions[i].z);
            if (uv.size() > 0)
            {
                data.push_back(uv[i].x);
                data.push_back(uv[i].y);
            }
            if (normals.size() > 0)
            {
                data.push_back(normals[i].x);
                data.push_back(normals[i].y);
                data.push_back(normals[i].z);
            }
        }
        glBindVertexArray(sphereVAO);
        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        glBufferData(GL_ARRAY_BUFFER, data.size() * sizeof(float), &data[0], GL_STATIC_DRAW);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices.size() * sizeof(unsigned int), &indices[0], GL_STATIC_DRAW);
        float stride = (3 + 2 + 3) * sizeof(float);
        glEnableVertexAttribArray(0);
        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, stride, (void*)0);
        glEnableVertexAttribArray(1);
        glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, stride, (void*)(3 * sizeof(float)));
        glEnableVertexAttribArray(2);
        glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, stride, (void*)(5 * sizeof(float)));
    }

    glBindVertexArray(sphereVAO);
    glDrawElements(GL_TRIANGLE_STRIP, indexCount, GL_UNSIGNED_INT, 0);
}

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