OpenGL光照之材质

参考：

https://learnopenglcn.github.io/02%20Lighting/03%20Materials/

如果我们想要在OpenGL中模拟多种类型的物体，我们必须为每个物体分别定义一个材质(Material)属性.

当描述一个物体的时候，我们可以用这三个分量来定义一个材质颜色(Material Color)：环境光照(Ambient Lighting)、漫反射光照(Diffuse Lighting)和镜面光照(Specular Lighting).

再添加反光度(Shininess)这个分量到上述的三个颜色中，这就有我们需要的所有材质属性了

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

uniform Material material;

在片元着色器中，我们创建一个结构体(Struct)来储存物体的材质属性，我们在片元着色器中创建了一个材质结构体的uniform，所以下面我们希望修改一下光照的计算来顺应新的材质属性。由于所有材质变量都储存在结构体中，我们可以从uniform变量material中访问它们

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);
}

可以在程序中设置适当的uniform，对物体设置材质了。

GLSL中的结构体在设置uniform时并没有什么特别之处。

结构体只是作为uniform变量的一个封装，所以如果想填充这个结构体的话，我们仍需要对每个单独的uniform进行设置，但这次要带上结构体名的前缀

lightingShader.setVec3("material.ambient",  1.0f, 0.5f, 0.31f);
lightingShader.setVec3("material.diffuse",  1.0f, 0.5f, 0.31f);
lightingShader.setVec3("material.specular", 0.5f, 0.5f, 0.5f);
lightingShader.setFloat("material.shininess", 32.0f);

运行程序得到以下结果

OpenGL光照之材质

显然图片太亮了，这是因为没有控制强度,前面的教程，我们通过使用一个强度值改变环境光和镜面光强度的方式解决了这个问题.

光源对环境光、漫反射和镜面光分量具有着不同的强度

可以用同样的方式修改光源的漫反射和镜面光强度,为光照属性创建一个与材质结构体类似的结构体

struct Light {
    vec3 position;

    vec3 ambient;
    vec3 diffuse;
    vec3 specular;
};

uniform Light light;

和材质uniform一样，我们需要更新片元着色器

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

接下来在程序中设置光照强度

lightingShader.setVec3("light.ambient",  0.2f, 0.2f, 0.2f);
lightingShader.setVec3("light.diffuse",  0.5f, 0.5f, 0.5f); // 将光照调暗了一些以搭配场景
lightingShader.setVec3("light.specular", 1.0f, 1.0f, 1.0f);

然后结果如下

OpenGL光照之材质

可以利用sin和glfwGetTime函数改变光源的环境光和漫反射颜色，从而很容易地让光源的颜色随着时间变化

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

lightingShader.setVec3("light.ambient", ambientColor);
lightingShader.setVec3("light.diffuse", diffuseColor);

完整代码如下

#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include "shader.h"
#include <iostream>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include "Camera.h"
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"
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);

const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;


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;

float deltaTime = 0.0f;	
float lastFrame = 0.0f;

glm::vec3 lightPos(1.2f, 1.0f, 2.0f);
int main(void)
{
	//初始化glfw并创建窗口
	//-------------------
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
	GLFWwindow * window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "window", NULL, NULL);
	if (window == NULL)
	{
		std::cout << "Failed to create GLFW window" << std::endl;
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
	glfwSetCursorPosCallback(window, mouse_callback);
	glfwSetScrollCallback(window, scroll_callback);
	glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);

	//初始化GLAD
	//--------
	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
		std::cout << "Failed to initialize GLAD" << std::endl;
		return -1;
	}
	glEnable(GL_DEPTH_TEST);
	//创建着色器
	//---------
	Shader lightingShader("D:\\OpenGL\\Project1\\lightshader.vs", "D:\\OpenGL\\Project1\\lightshader.fs");
	Shader lampShader("D:\\OpenGL\\Project1\\4.1.texture.vs", "D:\\OpenGL\\Project1\\4.1.texture.fs");

	//设置顶点坐标，颜色，纹理坐标
	//--------
	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
	};

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

	unsigned int lightVAO;
	glGenVertexArrays(1, &lightVAO);
	glBindVertexArray(lightVAO);


	glBindBuffer(GL_ARRAY_BUFFER, VBO);

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(0);



	while (!glfwWindowShouldClose(window))
	{
		float currentFrame = glfwGetTime();
		deltaTime = currentFrame - lastFrame;
		lastFrame = currentFrame;

		processInput(window);

		glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

		lightingShader.use();
		lightingShader.setVec3("light.position", lightPos);
		lightingShader.setVec3("viewPos", camera.Position);

		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); // decrease the influence
		glm::vec3 ambientColor = diffuseColor * glm::vec3(0.2f); // low influence
		lightingShader.setVec3("light.ambient", ambientColor);
		lightingShader.setVec3("light.diffuse", diffuseColor);
		lightingShader.setVec3("light.specular", 1.0f, 1.0f, 1.0f);

		lightingShader.setVec3("material.ambient", 1.0f, 0.5f, 0.31f);
		lightingShader.setVec3("material.diffuse", 1.0f, 0.5f, 0.31f);
		lightingShader.setVec3("material.specular", 0.5f, 0.5f, 0.5f); // specular lighting doesn't have full effect on this object's material
		lightingShader.setFloat("material.shininess", 32.0f);


		glm::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);


		glm::mat4 model = glm::mat4(1.0f);
		lightingShader.setMat4("model", model);



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

		lampShader.use();
		lampShader.setMat4("projection", projection);
		lampShader.setMat4("view", view);
		model = glm::mat4(1.0f);
		model = glm::translate(model, lightPos);
		model = glm::scale(model, glm::vec3(0.2f)); // a smaller cube
		lampShader.setMat4("model", model);


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

		glfwSwapBuffers(window);
		glfwPollEvents();
	}
	glDeleteVertexArrays(1, &cubeVAO);
	glDeleteVertexArrays(1, &lightVAO);
	glDeleteBuffers(1, &VBO);

	glfwTerminate();
	return 0;


}
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);
	if (glfwGetKey(window, GLFW_KEY_E) == GLFW_PRESS)
		camera.ProcessKeyboard(UP, deltaTime);
	if (glfwGetKey(window, GLFW_KEY_Q) == GLFW_PRESS)
		camera.ProcessKeyboard(DOWN, deltaTime);
}

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{

	glViewport(0, 0, width, height);
}
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 top

	lastX = xpos;
	lastY = ypos;

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

light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);
}

light片元着色器

#version 330 core
out vec4 FragColor;

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

struct Light {
    vec3 position;

    vec3 ambient;
    vec3 diffuse;
    vec3 specular;
};

in vec3 FragPos;  
in vec3 Normal;  
  
uniform vec3 viewPos;
uniform Material material;
uniform Light light;

void main()
{
    // ambient
    vec3 ambient = light.ambient * material.ambient;
  	
    // diffuse 
    vec3 norm = normalize(Normal);
    vec3 lightDir = normalize(light.position - FragPos);
    float diff = max(dot(norm, lightDir), 0.0);
    vec3 diffuse = light.diffuse * (diff * material.diffuse);
    
    // 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);
}

OpenGL光照之材质

参考：

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