OpenGL基础17：颜色

2024-02-29 13:36:10

一、RGB三原色

回想一下初中物理知识：

三原色：自然界中所有的颜色都可以用红、绿、蓝(RGB)这三种颜色频率的不同强度组合而得，白色包含了所有颜色
能看到一个物体的颜色，是这个物体(Reflected)反射的颜色，换句话说，就是不能被当前物体吸收(Absorb)的颜色
之所以能看到五彩斑斓的世界，是因为存在光源（发光的物体），否则将是完全的黑暗
结合②③，颜色从光源到我们的眼睛，大致就是这样一个过程：光源发出光线 → 照射到物体上 → 物体反射所有光源中存在，但不能被其吸收的颜色

计算机如何表示颜色（应该算是个很基础的东西了）：

RGBA：RGB代表3原色，一般在(0, 255)的范围内，越大对应颜色越深，A代表透明度，可以转换成对应浮点数，例如0.5就等于128（HEX格式：#FFB6C1FF → 对应RGBA格式：255,182,193, 255）
由①可见，计算机能表现的颜色数量其实是有限的，总共（256 * 256 * 256）种不同颜色，这也是所谓的 8-bit 采样，现在部分支持 10 - bit 采样，在这种情况下能表现出总共 (1024 * 1024 * 1024) 种不同颜色

二、光照场景

回想 OpenGL基础5：第一个正方形这一章

在这一章的时候，还没有接触到纹理，在颜色方面，也只是随便给他赋了个颜色

在此之后用了纹理，也就是简简单单的把颜色这一属性去掉了

现在重新考虑颜色这一属性，不再简单给物体随便赋颜色了，而是直接开始模拟光照！以给与物体一个真实的“颜色”，在此之前，先用前面的知识生成一个这样的场景：

其中白色的正方体是光源，珊瑚红色的正方体是物体

白色光源的着色器代码如下（LightFShader.txt 和 LightVShader）：

#version 330 core
out vec4 color;
void main()
{
    color = vec4(1.0f);
}

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

#version 330 core
layout (location = 0) in vec3 position;
uniform mat4 model;             //模型矩阵
uniform mat4 view;              //观察矩阵
uniform mat4 projection;        //投影矩阵
void main()
{
    gl_Position = projection * view * model * vec4(position, 1.0);
}

珊瑚红物体的着色器如下（ObjFShader.txt 和 ObjVShader）：

#version 330 core
out vec4 color;
uniform vec3 objectColor;
uniform vec3 lightColor;
in vec2 texIn;
uniform sampler2D texOutA;
void main()
{
    color = vec4(lightColor * objectColor, 1.0f);
}

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

#version 330 core
layout (location = 0) in vec3 position;
layout (location = 1) in vec2 texture;
out vec2 texIn;
uniform mat4 model;             //模型矩阵
uniform mat4 view;              //观察矩阵
uniform mat4 projection;        //投影矩阵
void main()
{
    gl_Position = projection * view * model * vec4(position, 1.0);
    //texIn = vec2(texture.x, 1.0f - texture.y);   //暂时屏蔽纹理
}

对于物体的顶点着色器，我们定义了两个uniform变量，分别代表着物体颜色和光照颜色

当我们把光源的颜色与物体的颜色相乘，所得到的就是这个物体所反射该光源的颜色(也就是我们感知到的颜色)

接下来就是主代码（Camera.h 和 Shader.h未改变，可以从前面的章节中找到）：

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

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

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

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

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

        -0.5f,  0.5f, -0.5f,  0.0f, 1.0f,
         0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
         0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
         0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
        -0.5f,  0.5f,  0.5f,  0.0f, 0.0f,
        -0.5f,  0.5f, -0.5f,  0.0f, 1.0f
    };
    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, 5 * sizeof(GLfloat), (GLvoid*)0);
    glEnableVertexAttribArray(0);
    /*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, 5 * sizeof(GLfloat), (GLvoid*)0);
    //VBO数据已经绑定且我们就用之前的顶点数据，所以无需再管理VBO
    glEnableVertexAttribArray(0);

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

    glEnable(GL_DEPTH_TEST);
    while (!glfwWindowShouldClose(window))
    {
        glfwPollEvents();
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);
        glClear(GL_DEPTH_BUFFER_BIT);
        cameraMove();

        //glBindTexture(GL_TEXTURE_2D, texture);
        shaderObj.Use();
        GLint objectColorLoc = glGetUniformLocation(shaderObj.Program, "objectColor");
        GLint lightColorLoc = glGetUniformLocation(shaderObj.Program, "lightColor");
        glUniform3f(objectColorLoc, 1.0f, 0.5f, 0.31f);     //物体反射颜色
        glUniform3f(lightColorLoc, 1.0f, 1.0f, 1.0f);       //光源：默认为白色
        glm::mat4 model = glm::mat4(1.0f);
        glm::mat4 view = glm::mat4(1.0f);
        glm::mat4 projection = glm::mat4(1.0f);
        model = glm::rotate(model, glm::radians(57.0f), glm::vec3(-0.5f, 1.0f, 0.0f));
        view = camera.GetViewMatrix();
        projection = glm::perspective(glm::radians(camera.Zoom), (GLfloat)WIDTH / (GLfloat)HEIGHT, 0.1f, 100.0f);
        GLint modelLoc = glGetUniformLocation(shaderObj.Program, "model");
        GLint viewLoc = glGetUniformLocation(shaderObj.Program, "view");
        GLint 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);

        //glBindTexture(GL_TEXTURE_2D, 0);
        shaderLight.Use();
        model = glm::translate(glm::mat4(1.0f), lightPos);
        model = glm::scale(model, glm::vec3(0.2f));
        modelLoc = glGetUniformLocation(shaderLight.Program, "model");
        viewLoc = glGetUniformLocation(shaderLight.Program, "view");
        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);

        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)           //如果当前是按下操作
        keys[key] = true;
    else if (action == GLFW_RELEASE)            //松开键盘
        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);
}

码农公寓

一、RGB三原色

二、光照场景

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