在著色器中使用漫反射貼圖的方法和紋理教程中是完全一樣的。但這次我們會將紋理儲存為Material結構體中的一個sampler2D。我們將之前定義的vec3漫反射顏色向量替換為漫反射貼圖。

注意sampler2D是所謂的不透明類型(Opaque Type)，也就是說我們不能將它實例化，只能通過uniform來定義它。如果我們使用除uniform以外的方法（比如函數的參數）實例化這個結構體，GLSL會拋出一些奇怪的錯誤。這同樣也適用于任何封裝了不透明類型的結構體。

我們也移除了環境光材質顏色向量，因為環境光顏色在幾乎所有情況下都等于漫反射顏色，所以我們不需要將它們分開儲存：

struct Material {sampler2D diffuse;vec3      specular;float     shininess;
}; 
...
in vec2 TexCoords;

如果你非常固執，仍想將環境光顏色設置為一個（漫反射值之外）不同的值，你也可以保留這個環境光的vec3，但整個物體仍只能擁有一個環境光顏色。如果想要對不同片段有不同的環境光值，你需要對環境光值單獨使用另外一個紋理。

注意我們將在片段著色器中再次需要紋理坐標，所以我們聲明一個額外的輸入變量。接下來我們只需要從紋理中采樣片段的漫反射顏色值即可：

vec3 diffuse = light.diffuse * diff * vec3(texture(material.diffuse, TexCoords));

不要忘記將環境光得材質顏色設置為漫反射材質顏色同樣的值。

vec3 ambient = light.ambient * vec3(texture(material.diffuse, TexCoords));

這就是使用漫反射貼圖的全部步驟了。你可以看到，這并不是什么新的東西，但這能夠極大地提高視覺品質。為了讓它正常工作，我們還需要使用紋理坐標更新頂點數據，將它們作為頂點屬性傳遞到片段著色器，加載材質并綁定材質到合適的紋理單元。

更新后的頂點數據可以在這里找到。頂點數據現在包含了頂點位置、法向量和立方體頂點處的紋理坐標。讓我們更新頂點著色器來以頂點屬性的形式接受紋理坐標，并將它們傳遞到片段著色器中：

#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aNormal;
layout (location = 2) in vec2 aTexCoords;
...
out vec2 TexCoords;void main()
{...TexCoords = aTexCoords;
}

記得去更新兩個VAO的頂點屬性指針來匹配新的頂點數據，并加載箱子圖像為一個紋理。在繪制箱子之前，我們希望將要用的紋理單元賦值到material.diffuse這個uniform采樣器，并綁定箱子的紋理到這個紋理單元：

lightingShader.setInt("material.diffuse", 0);
...
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, diffuseMap);

使用了漫反射貼圖之后，細節再一次得到驚人的提升，這次箱子有了光照開始閃閃發光（字面意思也是）了。你的箱子看起來可能像這樣：

#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <stb_image.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <learnopengl/filesystem.h>
#include <learnopengl/shader_m.h>
#include <learnopengl/camera.h>
#include <iostream>// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;// camera
Camera camera(glm::vec3(0.0f, 0.0f, 3.0f));
float lastX = SCR_WIDTH / 2.0f;
float lastY = SCR_HEIGHT / 2.0f;
bool firstMouse = true;// timing
float deltaTime = 0.0f;
float lastFrame = 0.0f;// lighting
glm::vec3 lightPos(1.2f, 1.0f, 2.0f);// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
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);
}// 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)
{if (firstMouse){lastX = xpos;lastY = ypos;firstMouse = false;}float xoffset = xpos - lastX;float yoffset = lastY - ypos; // reversed since y-coordinates go from bottom to toplastX = xpos;lastY = ypos;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;
}int main()
{// glfw: initialize and configureglfwInit();glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);// glfw window creationGLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);glfwMakeContextCurrent(window);glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);glfwSetCursorPosCallback(window, mouse_callback);glfwSetScrollCallback(window, scroll_callback);// tell GLFW to capture our mouseglfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);// glad: load all OpenGL function pointersif (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)){std::cout << "Failed to initialize GLAD" << std::endl;return -1;}// configure global opengl stateglEnable(GL_DEPTH_TEST);// build and compile our shader zprogramShader lightingShader("4.2.lighting_maps.vs", "4.2.lighting_maps.fs");Shader lampShader("4.2.lamp.vs", "4.2.lamp.fs");// set up vertex data (and buffer(s)) and configure vertex attributesfloat 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};// first, configure the cube's VAO (and VBO)unsigned int VBO, cubeVAO;glGenVertexArrays(1, &cubeVAO);glGenBuffers(1, &VBO);glBindBuffer(GL_ARRAY_BUFFER, VBO);glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);glBindVertexArray(cubeVAO);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);// second, configure the light's VAO (VBO stays the same; the vertices are the same for the light object which is also a 3D cube)unsigned int lightVAO;glGenVertexArrays(1, &lightVAO);glBindVertexArray(lightVAO);glBindBuffer(GL_ARRAY_BUFFER, VBO);// note that we update the lamp's position attribute's stride to reflect the updated buffer dataglVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);glEnableVertexAttribArray(0);// load textures (we now use a utility function to keep the code more organized)unsigned int diffuseMap = loadTexture(FileSystem::getPath("resources/textures/container2.png").c_str());unsigned int specularMap = loadTexture(FileSystem::getPath("resources/textures/container2_specular.png").c_str());// shader configurationlightingShader.use();lightingShader.setInt("material.diffuse", 0);lightingShader.setInt("material.specular", 1);// render loopwhile (!glfwWindowShouldClose(window)){// per-frame time logicfloat currentFrame = glfwGetTime();deltaTime = currentFrame - lastFrame;lastFrame = currentFrame;// inputprocessInput(window);// renderglClearColor(0.1f, 0.1f, 0.1f, 1.0f);glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);// be sure to activate shader when setting uniforms/drawing objectslightingShader.use();lightingShader.setVec3("light.position", lightPos);lightingShader.setVec3("viewPos", camera.Position);// light propertieslightingShader.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);// material propertieslightingShader.setFloat("material.shininess", 64.0f);// view/projection transformationsglm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);glm::mat4 view = camera.GetViewMatrix();lightingShader.setMat4("projection", projection);lightingShader.setMat4("view", view);// world transformationglm::mat4 model;lightingShader.setMat4("model", model);// bind diffuse mapglActiveTexture(GL_TEXTURE0);glBindTexture(GL_TEXTURE_2D, diffuseMap);// bind specular mapglActiveTexture(GL_TEXTURE1);glBindTexture(GL_TEXTURE_2D, specularMap);// render the cubeglBindVertexArray(cubeVAO);glDrawArrays(GL_TRIANGLES, 0, 36);// also draw the lamp objectlampShader.use();lampShader.setMat4("projection", projection);lampShader.setMat4("view", view);model = glm::mat4();model = glm::translate(model, lightPos);model = glm::scale(model, glm::vec3(0.2f)); // a smaller cubelampShader.setMat4("model", model);glBindVertexArray(lightVAO);glDrawArrays(GL_TRIANGLES, 0, 36);// 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:glDeleteVertexArrays(1, &cubeVAO);glDeleteVertexArrays(1, &lightVAO);glDeleteBuffers(1, &VBO);// glfw: terminate, clearing all previously allocated GLFW resources.glfwTerminate();return 0;
}

如果添加一個叫做放射光貼圖(Emission Map)的東西，它是一個儲存了每個片段的發光值(Emission Value)的貼圖。發光值是一個包含（假設）光源的物體發光(Emit)時可能顯現的顏色，這樣的話物體就能夠忽略光照條件進行發光(Glow)。游戲中某個物體在發光的時候，你通常看到的就是放射光貼圖。將這個紋理（作者為 creativesam）作為放射光貼圖添加到箱子上，需要添加的代碼有：

cpp

片元著色器：

#version 330 core
out vec4 FragColor;struct Material {sampler2D diffuse;sampler2D specular;    sampler2D emission;float shininess;
}; struct Light {vec3 position;vec3 ambient;vec3 diffuse;vec3 specular;
};in vec3 FragPos;  
in vec3 Normal;  
in vec2 TexCoords;uniform vec3 viewPos;
uniform Material material;
uniform Light light;void main()
{// ambientvec3 ambient = light.ambient * texture(material.diffuse, TexCoords).rgb;// diffuse vec3 norm = normalize(Normal);vec3 lightDir = normalize(light.position - FragPos);float diff = max(dot(norm, lightDir), 0.0);vec3 diffuse = light.diffuse * diff * texture(material.diffuse, TexCoords).rgb;  // specularvec3 viewDir = normalize(viewPos - FragPos);vec3 reflectDir = reflect(-lightDir, norm);  float spec = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess);vec3 specular = light.specular * spec * texture(material.specular, TexCoords).rgb;  // emissionvec3 emission = texture(material.emission, TexCoords).rgb;vec3 result = ambient + diffuse + specular + emission;FragColor = vec4(result, 1.0);
} 

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