C++ opengl 绘制立方体，贴图

纹理和纹理坐标是两个东西

texture(material.diffuse, TexCoords)这个方法，是从纹理中根据对应的纹理坐标取出对应的颜色值

texture(material.emission, TexCoords).rgb等同于vec3(texture(material.emission,TexCoords))其实就是把vec4转成vec3

vec3 result = ambient + diffuse + specular + emission;也就是说，你可以针对一个物体，对应不同的位置进行专门贴图，只要找到那个对应的纹理的对应的区域的颜色值即可

这个demo中使用的是同一个纹理坐标，其实也可以给各个纹理单独指定坐标

opengl_color_light_picture.cpp

#include <iostream>
#include <cmath>

#include "glad/glad.h"
#include "GLFW/glfw3.h"
#include "utils/Shader.h"
//图片工具库
#include "utils/stb_image.h"

//矩阵工具库
#include "utils/glm/glm.hpp"
#include "utils/glm/gtc/matrix_transform.hpp"
#include "utils/glm/gtc/type_ptr.hpp"
#include "utils/Camera.h"

void framebuffer_size_callback(GLFWwindow *window, int width, int height);

void processInput(GLFWwindow *window);

void loadTexture(unsigned int *texture, const char *path);

unsigned int loadTextureReal(char const * path);

void mouse_callback(GLFWwindow *window, double xpos, double ypos);

void scroll_callback(GLFWwindow *window, double xoffset, double yoffset);


glm::vec3 cameraPos = glm::vec3(0.0f, 0.0f, 3.0f);//相机位置
glm::vec3 cameraFront = glm::vec3(0.0f, 0.0f, -1.0f);//面对的方向,以这个为尺度更改观看的，其实就是单位速度
glm::vec3 cameraUp = glm::vec3(0.0f, 1.0f, 0.0f);//头顶的方向

float deltaTime = 0.0f; //当前帧与上一帧的时间差
float lastFrameTime = 0.0f;//上一帧的时间

float lastX = 300;
float lastY = 300;


Camera camera(glm::vec3(0.0f, 0.0f, 3.0f));
glm::vec3 lightPos(1.2f, 1.0f, 2.0f);


/**
 * 顶点数组对象：Vertex Array Object，VAO
 * 顶点缓冲对象：Vertex Buffer Object，VBO
 * 索引缓冲对象：Element Buffer Object，EBO或Index Buffer Object，IBO
 * @return
 */
int main() {
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_OPENGL_CORE_PROFILE);

    //第三个参数是标题
    GLFWwindow *window = glfwCreateWindow(600, 600, "LearnOpengl", NULL, NULL);
    if (window == NULL) {
        std::cout << "Fail to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    //奇特的写法，本应是个函数，写出来却像个变量，连参数都不需要传了
    if (!gladLoadGLLoader((GLADloadproc) glfwGetProcAddress)) {
        std::cout << "File to initialize GLAD" << std::endl;
        return -1;
    }
    //使窗口隐藏光标并且捕捉它
    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
    //使用回调
    glfwSetCursorPosCallback(window, mouse_callback);

    glViewport(0, 0, 600, 600);//指定视口大小，跟java一样
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
    glfwSetScrollCallback(window, scroll_callback);

    //加载纹理
    unsigned int diffuseMap, diffuse_specular_Map, matrixMap;
    const char *path1 = "D:\\cl_workspace\\TestOpengl\\resource\\container2.jpg";
    const char *path2 = "D:\\cl_workspace\\TestOpengl\\resource\\container2_specular.png";
    const char *path3 = "D:\\cl_workspace\\TestOpengl\\resource\\matrix.jpg";
//    //两个都要传递引用，这样函数更改的值才是上面的值
//    loadTexture(&diffuseMap, path1);
//    loadTexture(&diffuse_specular_Map, path2);
//    loadTexture(&matrixMap, path3);
    diffuseMap = loadTextureReal(path1);
    diffuse_specular_Map = loadTextureReal(path2);
    matrixMap = loadTextureReal(path3);
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, diffuseMap);
    glActiveTexture(GL_TEXTURE1);
    glBindTexture(GL_TEXTURE_2D, diffuse_specular_Map);
    glActiveTexture(GL_TEXTURE2);
    glBindTexture(GL_TEXTURE_2D, matrixMap);


    //箱子
    Shader lightingShader("D:\\cl_workspace\\TestOpengl\\shader\\vertex_shader_6.glsl",
                          "D:\\cl_workspace\\TestOpengl\\shader\\fragment_shader_6.glsl");
    //光源
    Shader lampShader("D:\\cl_workspace\\TestOpengl\\shader\\vertex_shader_4.glsl",
                      "D:\\cl_workspace\\TestOpengl\\shader\\fragment_shader_4.glsl");


    //立方体
    float vertices[] = {
            // positions          // normals           // texture coords
            -0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f,
            0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -1.0f, 1.0f, 0.0f,
            0.5f, 0.5f, -0.5f, 0.0f, 0.0f, -1.0f, 1.0f, 1.0f,
            0.5f, 0.5f, -0.5f, 0.0f, 0.0f, -1.0f, 1.0f, 1.0f,
            -0.5f, 0.5f, -0.5f, 0.0f, 0.0f, -1.0f, 0.0f, 1.0f,
            -0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f,

            -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f,
            0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f,
            0.5f, 0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 1.0f, 1.0f,
            0.5f, 0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 1.0f, 1.0f,
            -0.5f, 0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f,
            -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f,

            -0.5f, 0.5f, 0.5f, -1.0f, 0.0f, 0.0f, 1.0f, 0.0f,
            -0.5f, 0.5f, -0.5f, -1.0f, 0.0f, 0.0f, 1.0f, 1.0f,
            -0.5f, -0.5f, -0.5f, -1.0f, 0.0f, 0.0f, 0.0f, 1.0f,
            -0.5f, -0.5f, -0.5f, -1.0f, 0.0f, 0.0f, 0.0f, 1.0f,
            -0.5f, -0.5f, 0.5f, -1.0f, 0.0f, 0.0f, 0.0f, 0.0f,
            -0.5f, 0.5f, 0.5f, -1.0f, 0.0f, 0.0f, 1.0f, 0.0f,

            0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f,
            0.5f, 0.5f, -0.5f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f,
            0.5f, -0.5f, -0.5f, 1.0f, 0.0f, 0.0f, 0.0f, 1.0f,
            0.5f, -0.5f, -0.5f, 1.0f, 0.0f, 0.0f, 0.0f, 1.0f,
            0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f,
            0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f,

            -0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f, 0.0f, 1.0f,
            0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f, 1.0f, 1.0f,
            0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f, 1.0f, 0.0f,
            0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f, 1.0f, 0.0f,
            -0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f, 0.0f, 0.0f,
            -0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f, 0.0f, 1.0f,

            -0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f,
            0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f,
            0.5f, 0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f,
            0.5f, 0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f,
            -0.5f, 0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f,
            -0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f
    };


    //创建VBO，绑定数据，绑定VAO
    //明白了，VBO顶点缓冲区，是用来存放数据的，而VAO是调用数据的索引
    unsigned int cubeVAO;
    glGenVertexArrays(1, &cubeVAO);
    glBindVertexArray(cubeVAO);

    unsigned int VBO;
    glGenBuffers(1, &VBO);//&符号应该是传引用对象的意思，不然会传值进去
    glBindBuffer(GL_ARRAY_BUFFER, VBO);//这一步就是给GL_ARRAY_BUFFER绑定数据了
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    //做的时间长，反而忘了。。。这是给着色器里面的某个location设置值的
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void *) (0));
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void *) (3 * sizeof(float)));
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void *) (6 * sizeof(float)));
    glEnableVertexAttribArray(2);


    //当调用glBindVertexArray(lightVAO)后，再调用glBindBuffer(GL_ARRAY_BUFFER, VBO)
    //相当于把缓冲区中的数据设置给了lightVAO，上面的顺序一定不能变
    unsigned int lightVAO;
    glGenVertexArrays(1, &lightVAO);
    glBindVertexArray(lightVAO);

    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void *) (0));
    glEnableVertexAttribArray(0);

    //循环绘制
    while (!glfwWindowShouldClose(window)) {//判断界面是否关闭，没关闭就循环绘制
        processInput(window);

        //记录deltaTime
        float currentFrame = glfwGetTime();
        deltaTime = currentFrame - lastFrameTime;
        lastFrameTime = currentFrame;


        //同java
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);//如果开启了深度测试，这里就要把GL_DEPTH_BUFFER_BIT也清空

        //让光源随着时间的变化而改变位置
//        lightPos = glm::vec3(1.2f * sin(glfwGetTime()), 1.0f * sin(glfwGetTime()), 2.0f);

        glm::vec3 lightColor;
        lightColor.x = sin(glfwGetTime() * 2.0f);
        lightColor.y = sin(glfwGetTime() * 0.7f);
        lightColor.z = sin(glfwGetTime() * 1.3f);

        glm::vec3 diffuseColor = lightColor * glm::vec3(0.5f);//降低影响
        glm::vec3 ambientColor = diffuseColor * glm::vec3(0.2f);//环境光，更低
        //开启深度测试
        glEnable(GL_DEPTH_TEST);

        //lighting其实是物体。。。
        lightingShader.use();
        lightingShader.setVec3("lightPos", lightPos);//光源位置
        lightingShader.setVec3("viewPos", camera.Position);//观察位置

        //设置各个光照的强度
//        lightingShader.setVec3("light.ambient", ambientColor);
//        lightingShader.setVec3("light.diffuse", diffuseColor);
        lightingShader.setVec3("light.ambient", 0.2f, 0.2f, 0.2f);
        lightingShader.setVec3("light.diffuse", 0.5f, 0.5f, 0.5f);
        lightingShader.setVec3("light.specular", 1.0f, 1.0f, 1.0f);//镜面反射


        lightingShader.setInt("material.diffuse", 0);//绑定纹理?用0即可，0对应GL_TEXTURE0
        lightingShader.setInt("material.specular", 1);//绑定纹理?用1即可，1对应GL_TEXTURE1
        lightingShader.setInt("material.emission", 2);
//        lightingShader.setVec3("material.specular", 0.5f, 0.5f, 0.5f);
        lightingShader.setFloat("material.shininess", 64.0f);


        glm::mat4 model = glm::mat4();
        glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), 1.0f, 0.1f, 100.0f);
        glm::mat4 view = camera.GetViewMatrix();

        lightingShader.setMat4("model", model);
        lightingShader.setMat4("view", view);
        lightingShader.setMat4("projection", projection);

        glBindVertexArray(cubeVAO);
        glDrawArrays(GL_TRIANGLES, 0, 36);

        lampShader.use();
        lampShader.setMat4("view", view);
        lampShader.setMat4("projection", projection);
        model = glm::mat4();
        model = glm::translate(model, lightPos);
        model = glm::scale(model, glm::vec3(0.2f));
        lampShader.setMat4("model", model);

        glBindVertexArray(lightVAO);
        glDrawArrays(GL_TRIANGLES, 0, 36);


        //双缓冲机制，前缓冲保存着最终输出的图像，后缓冲则进行绘制，绘制完成以后与前缓冲交换，就会立即显示
        //单缓冲会存在闪烁问题
        glfwSwapBuffers(window);//交换颜色缓冲
        glfwPollEvents();//检查有没有什么触发事件，鼠标键盘等，并调用相关的回调

    }

    //回收数据
    glDeleteVertexArrays(1, &cubeVAO);
    glDeleteVertexArrays(1, &lightVAO);
    glDeleteBuffers(1, &VBO);

    glfwTerminate();//结束绘制
    return 0;
}

//窗口尺寸改变的回调
void framebuffer_size_callback(GLFWwindow *window, int width, int height) {
    glViewport(0, 0, width, height);
}

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);
}

//*代表引用传递，传参数时要用&符号，而取*里的值则需要*p
void loadTexture(unsigned int *texture, const char *path) {
    glGenTextures(1, texture);
//    对*p赋值，从而改变p所指的地址上说保存的值
    //*textrue就能表示这个内存地址上表示的值
    glBindTexture(GL_TEXTURE_2D, *texture);//GL_TEXTURE_2D同样，它也是一个目标
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);//设置环绕和过滤方式
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    //加载纹理，第三个参数是颜色通道的个数
    int width, height, nrChannels;
    stbi_set_flip_vertically_on_load(true);
    //图片
    unsigned char *data = stbi_load(path, &width,
                                    &height, &nrChannels, 0);

    //第二个参数为多级渐远纹理的级别，0为基本级别，第三个参数为指定纹理存储为何种格式
    //第六个总是设置为0，第七第八定义源图的格式和数据类型
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
    glGenerateMipmap(GL_TEXTURE_2D);
    //释放图像内存
    stbi_image_free(data);
}


unsigned int loadTextureReal(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;
}

bool firstMouse = true;

void mouse_callback(GLFWwindow *window, double xpos, double ypos) {
    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;

    camera.ProcessMouseMovement(xoffset, yoffset);
}

//滚轮的回调
void scroll_callback(GLFWwindow *window, double xoffset, double yoffset) {
    camera.ProcessMouseScroll(yoffset);
}

fragment_shader_6.glsl

#version 330 core
out vec4 FragColor;

uniform vec3 lightPos;
uniform vec3 viewPos;

in vec3 Normal;
in vec3 FragPos;

struct Material {
    //环境光颜色几乎在所有情况下都等于漫反射颜色，所以不需要环境光，只用漫反射即可
//    vec3 ambient;//环境光，一般是物体颜色
//    vec3 diffuse;//漫反射光照下物体的颜色
    sampler2D diffuse;
//    vec3 specular;//镜面光照对物体的颜色影响
    sampler2D specular;
    sampler2D emission;//放射光的贴图
    float shininess;//反光度
};

//一个光源对它的ambient、diffuse和specular光照有着不同的强度
struct Light {
    vec3 position;

    vec3 ambient;
    vec3 diffuse;
    vec3 specular;
};

//之前都是用灯光来设定环境光，漫反射光和镜面反射光，现在我们要分开设置这些材质
uniform Material material;

uniform Light light;

//上面用两个纹理，下面用一个接收？并不是，这个是纹理的坐标
//而纹理的对象，是设置给了Light结构体里的diffuse和specular
in vec2 TexCoords;

void main() {
       //环境光,现在设置为与漫反射同样的值
       vec3 ambient = light.ambient * vec3(texture(material.diffuse, TexCoords));

       //漫反射,先对向量进行标准化
       vec3 norm = normalize(Normal);
       vec3 lightDir = normalize(lightPos - FragPos);//光的方向向量是光源位置与片段位置之间的向量差
       //依据法向量计算光源对当前片段的漫反射影响
       float diff = max(dot(norm, lightDir),0.0);//点积，算出来的是投影长度,夹角越小，越接近1，越亮
       vec3 diffuse = light.diffuse * (diff * vec3(texture(material.diffuse, TexCoords)));//混合纹理

       //镜面反射
       vec3 viewDir = normalize(viewPos - FragPos);//片段位置到摄像机位置的向量,也就是视线方向
       //反射向量，reflect函数要求第一个向量是从光源指向片段位置的向量
       vec3 reflectDir = reflect(-lightDir,norm);
       //点乘，避免负值，取32次幂，32是高光的反光度，这个点乘肯定小于1，32次方，那就更小了
       //一个物体的反光度越高，反射光的能力越强，散射得越少，高光点就会越小,可以理解
       //反光度material.shininess，必须是float类型，否则报错
       //镜面光贴图我们可以可以对物体设置大量的细节，比如物体的哪些部分需要有闪闪发光的属性，我们甚至可以设置它们对应的强度。
       //镜面光贴图能够在漫反射贴图之上给予我们更高一层的控制
       float spec = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess);
       vec3 specular = light.specular * (spec * vec3(texture(material.specular,TexCoords)));

       //放射光贴图,这个.rgb跟前面的vec3()转是一个效果，都是把vec4转成vec3
       vec3 emission = texture(material.emission, TexCoords).rgb;

       //将环境光，漫反射光，镜面反射光作用于物体
       vec3 result = ambient + diffuse + specular + emission;
       //混合两个光照颜色
       FragColor = vec4(result, 1.0);

}

vertex_shader_6.glsl

#version 330 core

layout (location = 0) in vec3 aPos;//位置变量的属性位置值为0
layout (location = 1) in vec3 aNormal;//法向量
layout (location = 2) in vec2 aTexCoords;//纹理

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



out vec3 Normal;
out vec3 FragPos;
out vec2 TexCoords;

void main() {
    gl_Position = projection*view*model*vec4(aPos,1.0);
    FragPos = vec3(model * vec4(aPos,1.0));
    //把法向量也转换为世界空间坐标,所以需要一个法线矩阵
    //由于我们只在世界空间中进行操作（不是在观察空间），我们只使用模型矩阵
    //使用inverse和transpose函数修改model生成这个法线矩阵,必须是3x3的
    mat3 normalMatrix =  mat3(transpose(inverse(model)));
    Normal = normalMatrix * aNormal;
    TexCoords = aTexCoords;
}