OpenGL学习笔记七——光照2(实现冯氏光照模型)

冯氏光照模型构成

• 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)。它是冯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

把环境光照添加到场景里非常简单。添加环境光只需要在物体基础颜色上乘环境光颜色就是最终的收到环境光照的结果：

void main()
{
    float ambientStrength = 0.1;//光强
    vec3 ambient = ambientStrength * lightColor;//光照颜色

    vec3 result = ambient * objectColor;//最终颜色
    FragColor = vec4(result, 1.0);
}

漫反射

原理：

resultLight=max(Normal dot LightDir),0);//物体法向量点乘光的方向
因此使用漫反射需要以下数据：

• 法向量：一个垂直于顶点表面的向量。
  顶点法向量可作为顶点着色器的输入值传入

layout (location = 1) in vec3 aNormal;

• 定向的光线：作为光源的位置与片段的位置之间向量差的方向向量。为了计算这个光线，我们需要光的位置向量和片段的位置向量。
  光的方向可以定义一个全局变量：

uniform vec3 lightPos;

实例程序

顶点着色器

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

out vec3 FragPos;
out vec3 Normal;

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

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

片元着色器

#version 330 core
out vec4 FragColor;

in vec3 Normal;  
in vec3 FragPos;  
  
uniform vec3 lightPos; 
uniform vec3 lightColor;
uniform vec3 objectColor;

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);
} 

镜面反射

原理：

resultLight=pow（max(View dot ReflectLightDir,0)，Shininess）;//视线方向点乘光的反射方向，取反光度的幂

//FragPos为像素位置信息，viewPos可以理解为相机的位置
vec3 viewDir = normalize(viewPos - FragPos);
vec3 reflectDir = reflect(-lightDir, normal);
float spec = pow(max(dot(viewDir, reflectDir), 0.0), 32);
vec3 specular = specularStrength * spec * lightColor;

示例程序

顶点着色器

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

out vec3 FragPos;
out vec3 Normal;

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

void main()
{
    FragPos = vec3(model * vec4(aPos, 1.0));
    Normal = mat3(transpose(inverse(model))) * aNormal;  
    
    gl_Position = projection * view * vec4(FragPos, 1.0);
}

片元着色器

#version 330 core
out vec4 FragColor;

in vec3 Normal;  
in vec3 FragPos;  
  
uniform vec3 lightPos; 
uniform vec3 viewPos; 
uniform vec3 lightColor;
uniform vec3 objectColor;

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;
    
    // specular
    float specularStrength = 0.5;
    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;  
        
    vec3 result = (ambient + diffuse + specular) * objectColor;
    FragColor = vec4(result, 1.0);
} 

示例程序

#include <glad/glad.h>
#include <GLFW/glfw3.h>

#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

//#include"camera.h"
#include <iostream>

void framebuffer_size_callback(GLFWwindow* window, int width, int height);
// void mouse_callback(GLFWwindow* window, double xpos, double ypos);
// void scroll_callback(GLFWwindow* window, double xoffset, double yoffset);
 void processInput(GLFWwindow *window);

// 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);


const char *vertexShaderSource =
"#version 330 core\n"
"layout(location = 0) in vec3 aPos;\n"
"layout(location = 1) in vec3 aNormal;\n"

"out vec3 FragPos;\n"
"out vec3 Normal;\n"

"uniform mat4 model;\n"
"uniform mat4 view;\n"
"uniform mat4 projection;\n"

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

"gl_Position = projection * view * vec4(FragPos, 1.0);\n"
"}\n";

const char *fragmentShaderSource =
"#version 330 core\n"
"out vec4 FragColor;\n"

"in vec3 Normal;\n"
"in vec3 FragPos;\n"

"uniform vec3 lightPos;\n"
"uniform vec3 lightColor;\n"
"uniform vec3 objectColor;\n"

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

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

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


int main()
{
	//初始化
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);



	// 创建窗口
	GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
	if (window == NULL)
	{
		std::cout << "Failed to create GLFW window" << std::endl;
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

	// 错误提示信息
	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
		std::cout << "Failed to initialize GLAD" << std::endl;
		return -1;
	}

	// 开启深度测试（深度值粗略可视为与相机近平面的距离）
	glEnable(GL_DEPTH_TEST);

	//VertexShader创建顶点着色器
	int vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	glCompileShader(vertexShader);

	//Info获取编译出错信息
	int success;
	char info[512];
	glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(vertexShader, 512, NULL, info);
		std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << info << std::endl;
	}



	//片元着色器
	int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
	glCompileShader(fragmentShader);
	//编译信息
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragmentShader, 512, NULL, info);
		std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << info << std::endl;
	}


	//shaderProgramshader程序
	int shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragmentShader);
	glLinkProgram(shaderProgram);
	glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
	if (!success)
	{
		glGetProgramInfoLog(shaderProgram, 512, NULL, info);
		std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << info << std::endl;
	}


	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);
	float 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
	};
	// 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);

	// position attribute
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(0);
	// normal attribute
	glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)(3 * sizeof(float)));
	glEnableVertexAttribArray(1);

	glUseProgram(shaderProgram);


	// render loop
	// -----------
	while (!glfwWindowShouldClose(window))
	{
		// input
		// -----
		processInput(window);

		// render
		// ------
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // also clear the depth buffer now!


		// activate shader
		glUseProgram(shaderProgram);

		const glm::vec3 objectColor(1.0f, 0.5f, 0.31f);

		glUniform3fv(glGetUniformLocation(shaderProgram, "objectColor"), 1, &objectColor[0]);
		const glm::vec3 lightColor(1.0f, 1.0f, 1.0f);

		glUniform3fv(glGetUniformLocation(shaderProgram, "lightColor"), 1, &lightColor[0]);
		const glm::vec3 lightPos(1.0f, 0.5f, 0.31f);
		glUniform3fv(glGetUniformLocation(shaderProgram, "lightPos"), 1, &lightPos[0]);
		

		
	
		
		// create transformations
		glm::mat4 model = glm::mat4(1.0f); // make sure to initialize matrix to identity matrix first
		glm::mat4 view = glm::mat4(1.0f);
		glm::mat4 projection = glm::mat4(1.0f);
		model = glm::rotate(model, (float)glfwGetTime() * 100, glm::vec3(1.0f, 1.0f, 0.0f));
		view = glm::translate(view, glm::vec3(0.0f, 0.0f, -200.0f));
		projection = glm::perspective(glm::radians(80.0f), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 300.0f);
		// retrieve the matrix uniform locations
		unsigned int modelLoc = glGetUniformLocation(shaderProgram, "model");
		unsigned int viewLoc = glGetUniformLocation(shaderProgram, "view");

		glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(model));
		glUniformMatrix4fv(viewLoc, 1, GL_FALSE, &view[0][0]);

		glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "projection"), 1, GL_FALSE, &projection[0][0]);
		// render box
		glBindVertexArray(cubeVAO);
		glDrawArrays(GL_TRIANGLES, 0, 36);
		//glPolygonMode(GL_FRONT, GL_LINE);

		glfwSwapBuffers(window);
		glfwPollEvents();
	}


	glDeleteVertexArrays(1, &cubeVAO);
	glDeleteBuffers(1, &VBO);


	glfwTerminate();
	return 0;
}


void processInput(GLFWwindow *window)
{
	if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
		glfwSetWindowShouldClose(window, true);
}


void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
	glViewport(0, 0, width, height);
}