OpenGL基礎21：材質

一、材質

前面環境光、漫反射光照和鏡面光照都已經安排上了，但是物體的屬性是寫死的

在真實的世界裏，不同的物體會對光產生不同的反應，例如一顆金屬球或一塊橡木，它們在完全相同的光照下顯示出來的效果必然是不同的，前者以反射(Reflect)爲主，後者以散射(Scatter)爲主，如果想在OpenGL中模擬不同的材質，就必須爲每個物體定義材質(Material)屬性，~~儘管現在還是在用正方體~~

ambient：定義了在環境光照下這個物體反射的是什麼顏色，通常是和物體顏色相同的顏色
diffuse：定義了在漫反射光照下物體的顏色，通常是和物體顏色相同的顏色
specular：設置的是物體受到的鏡面光照影響的顏色，或者是反射一個物體特定的鏡面高光顏色
shininess：反光度，值越高，反射光的能力越強，散射得越少，高光點越小

#version 330 core
struct Material
{
    vec3 ambient;           //環境光
    vec3 diffuse;           //漫反射光色
    vec3 specular;          //鏡面光色
    float shininess;        //反光度
};

爲一個物體賦予一款正確的材質是非常困難的，這需要大量實驗和豐富的經驗，所以由於錯誤的設置材質而毀了物體的畫面質量是件經常發生的事

一樣修改片段着色器設置材質，這個時候不再寫死環境光強度、鏡面強度和反光度

void main()
{
    //環境光
    vec3 ambient = material.ambient * lightColor;

    //漫反射光
    vec3 norm = normalize(normalIn);
    vec3 lightDir = normalize(lightPos - fragPosIn);
    float diff = max(dot(norm, lightDir), 0.0f);
    vec3 diffuse = lightColor * (diff * material.diffuse);

    //鏡面光
    vec3 viewDir = normalize(viewPos - fragPosIn);
    vec3 reflectDir = reflect(-lightDir, norm);
    float spec = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess);
    vec3 specular = lightColor * (spec * material.specular);

    //混合
    vec3 result = ambient + diffuse + specular;
    color = vec4(result, 1.0f);
}

接下來我們在主代碼中將 ambient 和 diffuse 元素設置成想要讓物體所呈現的顏色，設置 specular 元素爲中等亮度顏色，同樣設置 shininess 爲 32，這樣 specular 元素對這個指定物體就不會產生過於強烈的影響

GLint matAmbientLoc = glGetUniformLocation(shaderObj.Program, "material.ambient");
GLint matDiffuseLoc = glGetUniformLocation(shaderObj.Program, "material.diffuse");
GLint matSpecularLoc = glGetUniformLocation(shaderObj.Program, "material.specular");
GLint matShineLoc = glGetUniformLocation(shaderObj.Program, "material.shininess");
glUniform3f(matAmbientLoc, 1.0f, 0.5f, 0.31f);
glUniform3f(matDiffuseLoc, 1.0f, 0.5f, 0.31f);
glUniform3f(matSpecularLoc, 0.5f, 0.5f, 0.5f);
glUniform1f(matShineLoc, 32.0f);

二、光的屬性

物體有了材質後，接下來再設置光的屬性

position：位置
ambient：環境光常數，一般默認爲一個比較小的值，對應之前的 ambientStrength
diffuse：總是光的顏色，影響漫反射
specular：全強度發光，影響鏡面反射

struct Light
{
    vec3 position;
    vec3 ambient;
    vec3 diffuse;
    vec3 specular;
};
uniform Light light;

接下來就是和材質一樣的套路了：

vec3 ambient = light.ambient * material.ambient;
vec3 diffuse = light.diffuse * (diff * material.diffuse);
vec3 specular = light.specular * (spec * material.specular);

一個完整的效果和代碼如下（青色瓷磚材質）：

#version 330 core
layout (location = 0) in vec3 position;
layout (location = 1) in vec2 texture;
layout (location = 2) in vec3 normal;
out vec2 texIn;
out vec3 normalIn;
out vec3 fragPosIn;
uniform mat4 model;             //模型矩陣
uniform mat4 view;              //觀察矩陣
uniform mat4 projection;        //投影矩陣
void main()
{
    gl_Position = projection * view * model * vec4(position, 1.0);
    //texIn = vec2(texture.x, 1.0f - texture.y);
    fragPosIn = vec3(model * vec4(position, 1.0f));
    normalIn = mat3(transpose(inverse(model))) * normal;
}

/////////////////////////////////////////////////////////////////////////

#version 330 core
struct Material
{
    vec3 ambient;           //環境光
    vec3 diffuse;           //漫反射光色
    vec3 specular;          //鏡面光色
    float shininess;        //反光度
};
struct Light
{
    vec3 position;
    vec3 ambient;
    vec3 diffuse;
    vec3 specular;
};
uniform Material material;
uniform Light light;

out vec4 color;
uniform vec3 viewPos;
in vec3 fragPosIn;
in vec2 texIn;
in vec3 normalIn;
uniform sampler2D texOutA;
void main()
{
    //環境光
    vec3 ambient = light.ambient * material.ambient;

    //漫反射光
    vec3 norm = normalize(normalIn);
    vec3 lightDir = normalize(light.position - fragPosIn);
    float diff = max(dot(norm, lightDir), 0.0f);
    vec3 diffuse = light.diffuse * (diff * material.diffuse);

    //鏡面光
    vec3 viewDir = normalize(viewPos - fragPosIn);
    vec3 reflectDir = reflect(-lightDir, norm);
    float spec = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess);
    vec3 specular = light.specular * (spec * material.specular);

    //混合
    vec3 result = ambient + diffuse + specular;
    color = vec4(result, 1.0f);
}

main.cpp：

#include<iostream>
#include<opengl/glew.h>
#define GLEW_STATIC
#include<GLFW/glfw3.h>
#include"Camera.h"
#include<glm/glm.hpp>
#include<glm/gtc/matrix_transform.hpp>
#include<glm/gtc/type_ptr.hpp>
#include"Shader.h"
#include<opengl/freeglut.h>
#include<SOIL.h>

bool keys[1024];
Camera camera;
GLfloat lastX, lastY;
bool firstMouse = true;
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode);
void scroll_callback(GLFWwindow* window, double xoffset, double yoffset);
void mouse_callback(GLFWwindow* window, double xpos, double ypos);
void cameraMove();
glm::vec3 lightPos(1.2f, 1.0f, 2.0f);
const GLuint WIDTH = 800, HEIGHT = 600;

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

    GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "LearnOpenGL", nullptr, nullptr);
    glfwMakeContextCurrent(window);
    glfwSetKeyCallback(window, key_callback);
    glfwSetCursorPosCallback(window, mouse_callback);
    glfwSetScrollCallback(window, scroll_callback);

    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
    glewExperimental = GL_TRUE;
    glewInit();

    int width, height;
    glfwGetFramebufferSize(window, &width, &height);
    glViewport(0, 0, width, height);

    Shader shaderObj("ObjVShader.txt", "ObjFShader.txt");
    Shader shaderLight("LightVShader.txt", "LightFShader.txt");

    GLfloat vertices[] = 
    {
        -0.5f, -0.5f, -0.5f,  0.0f,  0.0f, -1.0f,
         0.5f, -0.5f, -0.5f,  0.0f,  0.0f, -1.0f,
         0.5f,  0.5f, -0.5f,  0.0f,  0.0f, -1.0f,
         0.5f,  0.5f, -0.5f,  0.0f,  0.0f, -1.0f,
        -0.5f,  0.5f, -0.5f,  0.0f,  0.0f, -1.0f,
        -0.5f, -0.5f, -0.5f,  0.0f,  0.0f, -1.0f,

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

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

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

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

        -0.5f,  0.5f, -0.5f,  0.0f,  1.0f,  0.0f,
         0.5f,  0.5f, -0.5f,  0.0f,  1.0f,  0.0f,
         0.5f,  0.5f,  0.5f,  0.0f,  1.0f,  0.0f,
         0.5f,  0.5f,  0.5f,  0.0f,  1.0f,  0.0f,
        -0.5f,  0.5f,  0.5f,  0.0f,  1.0f,  0.0f,
        -0.5f,  0.5f, -0.5f,  0.0f,  1.0f,  0.0f
    };
    GLuint VBO, VAO, texture;
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);
    glGenTextures(1, &texture);

    glBindVertexArray(VAO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBindTexture(GL_TEXTURE_2D, texture);

    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)0);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
    glEnableVertexAttribArray(2);
    /*glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
    glEnableVertexAttribArray(1);

    int picWidth, picHeight;
    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);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    unsigned char* image = SOIL_load_image("Texture/wood.jpg", &picWidth, &picHeight, 0, SOIL_LOAD_RGB);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, picWidth, picHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
    glGenerateMipmap(GL_TEXTURE_2D);
    SOIL_free_image_data(image);
    glBindTexture(GL_TEXTURE_2D, 0);*/

    GLuint lightVAO;
    glGenVertexArrays(1, &lightVAO);
    glBindVertexArray(lightVAO);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)0);
    //VBO數據已經綁定且我們就用之前的頂點數據，所以無需再管理VBO
    glEnableVertexAttribArray(0);

    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);

    glEnable(GL_DEPTH_TEST);
    while (!glfwWindowShouldClose(window))
    {
        glfwPollEvents();
        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);
        glClear(GL_DEPTH_BUFFER_BIT);
        cameraMove();

        //glBindTexture(GL_TEXTURE_2D, 0);
        shaderLight.Use();
        lightPos.x = 1.0f + sin(glfwGetTime()) * 2.0f;
        lightPos.y = sin(glfwGetTime() / 2.0f) * 1.0f;
        glm::mat4 view = camera.GetViewMatrix();
        glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (GLfloat)WIDTH / (GLfloat)HEIGHT, 0.1f, 100.0f);
        glm::mat4 model = glm::translate(glm::mat4(1.0f), lightPos);
        model = glm::scale(model, glm::vec3(0.2f));
        GLint modelLoc = glGetUniformLocation(shaderLight.Program, "model");
        GLint viewLoc = glGetUniformLocation(shaderLight.Program, "view");
        GLint projLoc = glGetUniformLocation(shaderLight.Program, "projection");
        glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(model));
        glUniformMatrix4fv(viewLoc, 1, GL_FALSE, glm::value_ptr(view));
        glUniformMatrix4fv(projLoc, 1, GL_FALSE, glm::value_ptr(projection));

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

        //glBindTexture(GL_TEXTURE_2D, texture);
        shaderObj.Use();
        GLint matAmbientLoc = glGetUniformLocation(shaderObj.Program, "material.ambient");
        GLint matDiffuseLoc = glGetUniformLocation(shaderObj.Program, "material.diffuse");
        GLint matSpecularLoc = glGetUniformLocation(shaderObj.Program, "material.specular");
        GLint matShineLoc = glGetUniformLocation(shaderObj.Program, "material.shininess");
        glUniform3f(matAmbientLoc, 0.0f, 0.1f, 0.06f);
        glUniform3f(matDiffuseLoc, 0.0f, 0.50980392f, 0.50980392f);
        glUniform3f(matSpecularLoc, 0.50196078f, 0.50196078f, 0.50196078f);
        glUniform1f(matShineLoc, 32.0f);
        /*glUniform3f(matAmbientLoc, 1.0f, 0.5f, 0.31f);
        glUniform3f(matDiffuseLoc, 1.0f, 0.5f, 0.31f);
        glUniform3f(matSpecularLoc, 0.5f, 0.5f, 0.5f);
        glUniform1f(matShineLoc, 32.0f);*/

        GLint lightPosLoc = glGetUniformLocation(shaderObj.Program, "light.position");
        GLint lightAmbientLoc = glGetUniformLocation(shaderObj.Program, "light.ambient");
        GLint lightDiffuseLoc = glGetUniformLocation(shaderObj.Program, "light.diffuse");
        GLint lightSpecularLoc = glGetUniformLocation(shaderObj.Program, "light.specular");
        glUniform3f(lightAmbientLoc, 0.2f, 0.2f, 0.2f);
        glUniform3f(lightDiffuseLoc, 1.0f, 1.0f, 1.0f);
        glUniform3f(lightSpecularLoc, 1.0f, 1.0f, 1.0f);
        glUniform3f(lightPosLoc, lightPos.x, lightPos.y, lightPos.z);

        GLint viewPosLoc = glGetUniformLocation(shaderObj.Program, "viewPos");
        glUniform3f(viewPosLoc, camera.Position.x, camera.Position.y, camera.Position.z);
        model = glm::mat4(1.0f);
        model = glm::rotate(model, glm::radians(57.0f), glm::vec3(-0.5f, 1.0f, 0.0f));
        modelLoc = glGetUniformLocation(shaderObj.Program, "model");
        viewLoc = glGetUniformLocation(shaderObj.Program, "view");
        projLoc = glGetUniformLocation(shaderObj.Program, "projection");
        glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(model));
        glUniformMatrix4fv(viewLoc, 1, GL_FALSE, glm::value_ptr(view));
        glUniformMatrix4fv(projLoc, 1, GL_FALSE, glm::value_ptr(projection));

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

        glBindVertexArray(0);
        glfwSwapBuffers(window);
    }
    glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);
    glfwTerminate();
    return 0;
}


GLfloat deltaTime = 0.0f;
GLfloat lastFrame = 0.0f;
void cameraMove()
{
    GLfloat currentFrame = glfwGetTime();
    deltaTime = currentFrame - lastFrame;
    lastFrame = currentFrame;

    GLfloat cameraSpeed = 1.0f * deltaTime;
    if (keys[GLFW_KEY_W])
        camera.ProcessKeyboard(Camera_Movement(FORWARD), deltaTime);
    if (keys[GLFW_KEY_S])
        camera.ProcessKeyboard(Camera_Movement(BACKWARD), deltaTime);
    if (keys[GLFW_KEY_A])
        camera.ProcessKeyboard(Camera_Movement(LEFT), deltaTime);
    if (keys[GLFW_KEY_D])
        camera.ProcessKeyboard(Camera_Movement(RIGHT), deltaTime);
}

void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode)
{
    if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
        glfwSetWindowShouldClose(window, GL_TRUE);
    if (action == GLFW_PRESS)           //如果當前是按下操作
        keys[key] = true;
    else if (action == GLFW_RELEASE)            //鬆開鍵盤
        keys[key] = false;
}

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

void mouse_callback(GLFWwindow* window, double xpos, double ypos)
{
    if (firstMouse)
    {
        lastX = xpos;
        lastY = ypos;
        firstMouse = false;
    }
    GLfloat xoffset = xpos - lastX;
    GLfloat yoffset = lastY - ypos;
    lastX = xpos;
    lastY = ypos;
    
    GLfloat sensitivity = 0.05;
    xoffset *= sensitivity;
    yoffset *= sensitivity;
    
    camera.ProcessMouseMovement(xoffset, yoffset);
}

OpenGL基礎21：材質

一、材質

二、光的屬性

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OpenGL基礎27：網格

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