LearnOpenGL学习（光照 -- 颜色，基础光照，材质，光照贴图）

光照

glm::vec3 lightColor(0.0f, 1.0f, 0.0f);
glm::vec3 toyColor(1.0f, 0.5f, 0.31f);
glm::vec3 result = lightColor * toyColor; // = (0.0f, 0.5f, 0.0f);

说明：当我们把光源的颜色与物体的颜色值相乘，所得到的就是这个物体所反射的颜色。

创建一个光照场景

#shader vertex
#version 330 core

layout(location = 0) in vec3 aPos;

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

void main()
{
    gl_Position = projection * view * model * vec4(aPos, 1.0);
};

#shader fragment
#version 330 core

out vec4 FragColor;

uniform vec3 objectColor;
uniform vec3 lightColor;

void main()
{
    FragColor = vec4(lightColor * objectColor, 1.0);
};

很简单，只需要计算一个光照

摄像机从正方体正中心看过去显示一个正方形，我还以为写错了，查了半天错，头都秃了。。。。

#include "TestLightColor.h"

#include "Render.h"
#include "imgui/imgui.h"

#include <glm/ext/matrix_clip_space.hpp>
#include <glm/ext/matrix_transform.hpp>
#include <GLFW/glfw3.h>

namespace test {

    void TestLightColor_scroll_callback(GLFWwindow* window, double xoffset, double yoffset);
    void TestLightColor_mouse_callback(GLFWwindow* window, double xposIn, double yposIn);

    TestLightColor::TestLightColor() : camera(glm::vec3(0.0f,0.0f,6.0f)) {
        float vertices[] = {
        -0.5f, -0.5f, -0.5f,
         0.5f, -0.5f, -0.5f,
         0.5f,  0.5f, -0.5f,
         0.5f,  0.5f, -0.5f,
        -0.5f,  0.5f, -0.5f,
        -0.5f, -0.5f, -0.5f,

        -0.5f, -0.5f,  0.5f,
         0.5f, -0.5f,  0.5f,
         0.5f,  0.5f,  0.5f,
         0.5f,  0.5f,  0.5f,
        -0.5f,  0.5f,  0.5f,
        -0.5f, -0.5f,  0.5f,

        -0.5f,  0.5f,  0.5f,
        -0.5f,  0.5f, -0.5f,
        -0.5f, -0.5f, -0.5f,
        -0.5f, -0.5f, -0.5f,
        -0.5f, -0.5f,  0.5f,
        -0.5f,  0.5f,  0.5f,

         0.5f,  0.5f,  0.5f,
         0.5f,  0.5f, -0.5f,
         0.5f, -0.5f, -0.5f,
         0.5f, -0.5f, -0.5f,
         0.5f, -0.5f,  0.5f,
         0.5f,  0.5f,  0.5f,

        -0.5f, -0.5f, -0.5f,
         0.5f, -0.5f, -0.5f,
         0.5f, -0.5f,  0.5f,
         0.5f, -0.5f,  0.5f,
        -0.5f, -0.5f,  0.5f,
        -0.5f, -0.5f, -0.5f,

        -0.5f,  0.5f, -0.5f,
         0.5f,  0.5f, -0.5f,
         0.5f,  0.5f,  0.5f,
         0.5f,  0.5f,  0.5f,
        -0.5f,  0.5f,  0.5f,
        -0.5f,  0.5f, -0.5f,
        };

        unsigned int indices[] = {
            0,1,2,
            3,4,5,
            6,7,8,
            9,10,11,
            12,13,14,
            15,16,17,
            18,19,20,
            21,22,23,
            24,25,26,
            27,28,29,
            30,31,32,
            33,34,35
        };

        GLCall(glEnable(GL_BLEND));
        GLCall(glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA));

        m_VAO = std::make_unique<VertexArray>();
        
        m_VertexBuffer = std::make_unique<VertexBuffer>(vertices, sizeof(vertices));
        VertexBufferLayout layout;
        layout.Push<float>(3);
        m_VAO->AddBuffer(*m_VertexBuffer, layout);
        m_IndexBuffer = std::make_unique<IndexBuffer>(indices, 36);

        m_ColorShader = std::make_unique<Shader>("res/shaders/LightColor.shader"); 
        m_CubeShader = std::make_unique<Shader>("res/shaders/LightCube.shader");

        m_ColorShader->Bind();
        m_CubeShader->Bind();
    }

    TestLightColor::~TestLightColor() {

    }

    void TestLightColor::OnStart(GLFWwindow* window) {
        glEnable(GL_DEPTH_TEST);
        m_Window = window;

        glfwSetWindowUserPointer(m_Window, reinterpret_cast<void*>(this));

        glfwSetCursorPosCallback(m_Window, test::TestLightColor_mouse_callback);
        glfwSetScrollCallback(m_Window, test::TestLightColor_scroll_callback);

        glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
    }

    void TestLightColor::OnUpdate(float delteTime) {

    }

    void TestLightColor::OnRender() {
        processInput(m_Window);
        float currentFrame = static_cast<float>(glfwGetTime());
        deltaTime = currentFrame - lastFrame;
        lastFrame = currentFrame;

        constexpr Render render;

        //processInput(m_Window);

        GLCall(glClearColor(0.0f, 0.0f, 0.0f, 1.0f));
        GLCall(glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT));

        GLCall(m_ColorShader->Bind());

        //GLCall(m_ColorShader->SetUniform3f("objectColor", 1.0f, 0.5f, 0.31f));
        //GLCall(m_ColorShader->SetUniform3f("lightColor", 1.0f, 1.0f, 1.0f));

        //glm::mat4 projection = glm::mat4(1.0f);
        glm::mat4  projection = glm::perspective(glm::radians(camera.Zoom),
            (float)test::SCR_WIDTH / (float)test::SCR_HEIGHT, 0.1f, 100.0f);
        glm::mat4 view = camera.GetViewMatrix();
        GLCall(m_ColorShader->SetUniformMat4f("projection", projection));
        GLCall(m_ColorShader->SetUniformMat4f("view", view));

        glm::mat4 model = glm::mat4(1.0f);
        GLCall(m_ColorShader->SetUniformMat4f("model", model));

        GLCall(m_VAO->Bind());
        GLCall(render.Draw(*m_VAO, *m_IndexBuffer, *m_ColorShader));

        GLCall(m_VAO->Bind());
        GLCall(m_CubeShader->Bind());
        GLCall(m_CubeShader->SetUniformMat4f("projection", projection));
        GLCall(m_CubeShader->SetUniformMat4f("view", view));
        model = glm::mat4(1.0f);
        model = glm::translate(model, lightPos);
        model = glm::scale(model, glm::vec3(2.0f));
        m_CubeShader->SetUniformMat4f("model", model);
        GLCall(render.Draw(*m_VAO, *m_IndexBuffer, *m_CubeShader));
        
    }

    void TestLightColor::OnImGuiRender() {
    
    }

    void TestLightColor::mouse_callback(GLFWwindow* window, double xposIn, double yposIn) {
        float xpos = static_cast<float>(xposIn);
        float ypos = static_cast<float>(yposIn);

        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);
    }

    void TestLightColor::scroll_callback(GLFWwindow* window, double xoffset, double yoffset) {
        camera.ProcessMouseScroll(static_cast<float>(yoffset));
    }

    void TestLightColor_mouse_callback(GLFWwindow* window, double xposIn, double yposIn) {
        TestLightColor* light = reinterpret_cast<TestLightColor*>(glfwGetWindowUserPointer(window));
        light->mouse_callback(window, xposIn, yposIn);
    }

    void TestLightColor_scroll_callback(GLFWwindow* window, double xoffset, double yoffset) {
        TestLightColor* light = reinterpret_cast<TestLightColor*>(glfwGetWindowUserPointer(window));
        light->mouse_callback(window, xoffset, yoffset);
    }

}

基础光照

• **环境光照(Ambient Lighting)**：即使在黑暗的情况下，世界上通常也仍然有一些光亮（月亮、远处的光），所以物体几乎永远不会是完全黑暗的。为了模拟这个，我们会使用一个环境光照常量，它永远会给物体一些颜色。
• **漫反射光照(Diffuse Lighting)**：模拟光源对物体的方向性影响(Directional Impact)。它是风氏光照模型中视觉上最显著的分量。物体的某一部分越是正对着光源，它就会越亮。
• **镜面光照(Specular Lighting)**：模拟有光泽物体上面出现的亮点。镜面光照的颜色相比于物体的颜色会更倾向于光的颜色。

环境光照

void main()
{
    float ambientStrength = 0.1;
    vec3 ambient = ambientStrength * lightColor;

    vec3 result = ambient * objectColor;
    FragColor = vec4(result, 1.0);
}

漫反射光照

为了（只）得到两个向量夹角的余弦值，我们使用的是单位向量（长度为1的向量），所以我们需要确保所有的向量都是标准化的，否则点乘返回的就不仅仅是余弦值了

法向量

#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aNormal;
...

修改橙色方块的着色器：（增加了漫反射）

#shader vertex
#version 330 core

layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aNormal;

out vec3 Normal;
out vec3 FragPos;

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

void main()
{
    FragPos = vec3(model * vec4(aPos, 1.0));
    Normal = aNormal;

    gl_Position = projection * view * model * vec4(aPos, 1.0);
};

#shader fragment
#version 330 core

in vec3 Normal;
in vec3 FragPos;

out vec4 FragColor;

uniform vec3 objectColor;
uniform vec3 lightColor;
uniform vec3 lightPos;

void main()
{
    //ambient
    float ambientStrength = 0.1;
    vec3 ambient = ambientStrength * lightColor;

    //diffuse
    vec3 norm = normalize(Normal);
    vec3 lightDir = normalize(lightPos - FragPos);
    float diff = max(dot(norm, lightDir), 0.0);
    vec3 diffuse = diff * lightColor;

    vec3 result = (ambient + diffuse)* objectColor;
    FragColor = vec4(result, 1.0);
};

在顶点着色器中，我们可以使用inverse和transpose函数自己生成这个法线矩阵，这两个函数对所有类型矩阵都有效。注意我们还要把被处理过的矩阵强制转换为3×3矩阵，来保证它失去了位移属性以及能够乘以

vec3

的法向量。

Normal = mat3(transpose(inverse(model))) * aNormal;

镜面光照

//specular 
    float specularStrength = 0.5f;
    vec3 viewDir = normalize(viewPos - FragPos);
    vec3 reflectDir = reflect(-lightDir, norm);
    float spec = pow(max(dot(viewDir, reflectDir), 0.0), 32);
    vec3 specular = specularStrength * spec * lightColor;

在顶点着色器中实现的风氏光照模型叫做Gouraud着色(Gouraud Shading)，而不是风氏着色(Phong Shading)。记住，由于插值，这种光照看起来有点逊色。风氏着色能产生更平滑的光照效果。

材质

#version 330 core
struct Material {
    vec3 ambient;
    vec3 diffuse;
    vec3 specular;
    float shininess;
}; 

uniform Material material;

在片段着色器中，我们创建一个结构体(Struct)来储存物体的材质属性。我们也可以把它们储存为独立的uniform值，但是作为一个结构体来储存会更有条理一些

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

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

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

    vec3 result = ambient + diffuse + specular;
    FragColor = vec4(result, 1.0);
}

忘写分号。。。

光的属性

物体过亮的原因是环境光、漫反射和镜面光这三个颜色对任何一个光源都全力反射。

如果我们假设 lightcolor 是 1.0，那么代码会是这样的：

vec3 ambient  = vec3(1.0) * material.ambient;
vec3 diffuse  = vec3(1.0) * (diff * material.diffuse);
vec3 specular = vec3(1.0) * (spec * material.specular);

所以物体的每个材质属性对每一个光照分量都返回了最大的强度。

为光照属性创建类似材质结构体的东西：

struct Light {
    vec3 position;

    vec3 ambient;
    vec3 diffuse;
    vec3 specular;
};

uniform Light light;

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

调节各种类型的光的强度

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); // 很低的影响

        GLCall(m_ColorShader->Bind());

        GLCall(m_ColorShader->SetUniform3f("light.ambient", ambientColor));
        GLCall(m_ColorShader->SetUniform3f("light.diffuse", diffuseColor));

改变光源的环境光和漫反射颜色，让其随着时间变化

光照贴图

漫反射贴图

注意** sampler2D** 是所谓的不透明类型(Opaque Type)，也就是说我们不能将它实例化，只能通过uniform来定义它。如果我们使用除uniform以外的方法（比如函数的参数）实例化这个结构体，GLSL会抛出一些奇怪的错误。这同样也适用于任何封装了不透明类型的结构体。

使用贴图

#shader vertex
#version 330 core

layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aNormal;
layout (location = 2) in vec2 aTexCoords;

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

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

void main()
{
    FragPos = vec3(model * vec4(aPos, 1.0));
    Normal = aNormal;
    TexCoords = aTexCoords;

    gl_Position = projection * view * model * vec4(aPos, 1.0);
};

#shader fragment
#version 330 core

in vec3 Normal;
in vec3 FragPos;

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

struct Material {
    sampler2D diffuse;
    vec3 specular;
    float shininess;
};

in vec2 TexCoords;

out vec4 FragColor;

uniform Light light;
uniform Material material;
uniform vec3 lightPos;
uniform vec3 viewPos;

void main()
{
    //ambient
    vec3 ambient = light.ambient * vec3(texture(material.diffuse, TexCoords));

    //diffuse
    vec3 norm = normalize(Normal);
    vec3 lightDir = normalize(lightPos - FragPos);
    float diff = max(dot(norm, lightDir), 0.0);
    vec3 diffuse = light.diffuse * diff * vec3(texture(material.diffuse, TexCoords));

    //specular 
    vec3 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 * material.specular);

    vec3 result = ambient + diffuse + specular;
    FragColor = vec4(result, 1.0);
};

镜面光贴图

链接：container2_specular.png (500×500)

我们想要让物体的某些部分以不同的强度显示镜面高光。我们可以使用一个专门用于镜面高光的纹理贴图。这也就意味着我们需要生成一个黑白的（如果你想得话也可以是彩色的）纹理，来定义物体每部分的镜面光强度。

镜面光贴图上的每个像素都可以由一个颜色向量来表示，一个像素越「白」，乘积就会越大，物体的镜面光分量就会越亮。

采样镜面光贴图

//cpp
lightingShader.setInt("material.specular", 1);
...
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, specularMap);

//shader
struct Material {
    sampler2D diffuse;
    sampler2D specular;
    float     shininess;
};

vec3 ambient  = light.ambient  * vec3(texture(material.diffuse, TexCoords));
vec3 diffuse  = light.diffuse  * diff * vec3(texture(material.diffuse, TexCoords));  
vec3 specular = light.specular * spec * vec3(texture(material.specular, TexCoords));
FragColor = vec4(ambient + diffuse + specular, 1.0);

通过使用镜面光贴图我们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。

参考：颜色 - LearnOpenGL CN

基础光照 - LearnOpenGL CN