OpenGL基础24：聚光灯

前置：OpenGL基础23：平行光与点光源

一、聚光灯

三种基础光源在上一章讲了2种，现在只剩下聚光灯了

手电筒就是一个很经典例子，相对于点光源，聚光灯拥有以下特点

依然有衰减，但是聚光灯的光照一般都是非常强的（也就是有着非常远的射程）
有一定的范围，在这个范围外光照极速衰减，距离聚光方向超过一定角度，哪怕离光源很近，也有可能完全没有光照
依上，既有位置属性，又有方向属性（聚光方向）

相对于点光源，聚光灯会额外多出2个属性：聚光方向和切光角

如下图：其中 $\theta$ 就是入射光向量与聚光方向的夹角， $\phi$ 就是切光角，显然

如果 $\theta$ 比 $\phi$ 大，那么当前入射光的光强就可以直接忽略
在 $\phi$ 的范围内，离光源越近，当前片段受到的光照就越强

目的很明显了，求出 $cos{\theta}$ 和 $cos{\phi}$ 的大小

为了方便测试，先把之前的光源扔了，然后我们假设自己头上挂着个手电筒（就是以摄像机为聚光灯，并且聚光中心为我们视角的中央），着色器中再加入切光角和方向属性

glUniform3f(lightPosLoc, camera.Position.x, camera.Position.y, camera.Position.z);
glUniform3f(lightDirect, camera.Front.x, camera.Front.y, camera.Front.z);
glUniform1f(lightCutOff, glm::cos(glm::radians(12.5f)));

vec3 lightDir = normalize(light.position - fragPosIn);
float theta = dot(lightDir, normalize(-light.direction));
if(theta > light.cutOff)        //两个角度的余弦角相比，余弦值大的那个角度小
{//计算漫反射和镜面反射
}
else//只考虑环境光

其实改动并不大，可以看到效果：

二、边缘柔和

再看上面的效果，会感觉有点假，边缘太过“锋利”了，现实里，它应该有一个渐变的效果

很容易想到插值，这样的话就需要两个角度，也就是两个“切光角”：一个会给予一个聚光内圆锥，在内圆锥内的光强参数必定为1，另一个给予一个聚光外圆锥，在外圆锥外的光强参数必定为0（只有环境光），这样就可以在两个圆锥之间的那一小部分圆环内对光强进行插值，完美！

一样，设 $\phi$ 为内圆锥角， $\gamma$ 为外圆锥角，我们就可以得出当前点的光强 $I$ 为： $I = \frac{cos{\theta} - cos{\gamma}}{cos{\phi} - cos{\gamma}}$ ，其中 $I$ 保证其范围在 (0, 1)内

完整代码如下：

clamp(val, L, R)：确保val的值在 [L, R] 的范围内

#version 330 core
layout (location = 0) in vec3 position;
layout (location = 1) in vec3 normal;
layout (location = 2) in vec2 texture;
out vec2 texIn;
out vec3 normalIn;
out vec3 fragPosIn;
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);fragPosIn = vec3(model * vec4(position, 1.0f));normalIn = mat3(transpose(inverse(model))) * normal;
}#version 330 core
struct Material
{sampler2D diffuse;      //贴图sampler2D specular;     //镜面贴图sampler2D emission;     //放射贴图float shininess;        //反光度
};
struct Light
{vec3 position;vec3 direction;vec3 ambient;vec3 diffuse;vec3 specular;float k0, k1, k2;float cutOff, outCutOff;
};
uniform Material material;
uniform Light light;
out vec4 color;
uniform vec3 viewPos;
in vec2 texIn;
in vec3 fragPosIn;
in vec3 normalIn;
void main()
{//环境光vec3 ambient = light.ambient * vec3(texture(material.diffuse, texIn));vec3 diffuse = vec3(0.0f);vec3 specular = vec3(0.0f);float attenuation = 0;vec3 lightDir = normalize(light.position - fragPosIn);//聚光float theta = dot(lightDir, normalize(-light.direction));float lightSoft = clamp((theta - light.outCutOff) / (light.cutOff - light.outCutOff), 0.0f, 1.0f);//漫反射光vec3 norm = normalize(normalIn);float diff = max(dot(norm, lightDir), 0.0f);diffuse = light.diffuse * (diff * vec3(texture(material.diffuse, texIn)));//镜面光vec3 viewDir = normalize(viewPos - fragPosIn);vec3 reflectDir = reflect(-lightDir, norm);float spec = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess);specular = light.specular * (spec * vec3(texture(material.specular, texIn)));//点光源float dis = length(light.position - fragPosIn);attenuation = 1.0f / (light.k0 + light.k1 * dis + light.k2 * (dis * dis));//混合diffuse *= attenuation * lightSoft;specular *= attenuation * lightSoft;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,  0.0f,  0.0f,0.5f, -0.5f, -0.5f,  0.0f,  0.0f, -1.0f,  1.0f,  0.0f,0.5f,  0.5f, -0.5f,  0.0f,  0.0f, -1.0f,  1.0f,  1.0f,0.5f,  0.5f, -0.5f,  0.0f,  0.0f, -1.0f,  1.0f,  1.0f,-0.5f,  0.5f, -0.5f,  0.0f,  0.0f, -1.0f,  0.0f,  1.0f,-0.5f, -0.5f, -0.5f,  0.0f,  0.0f, -1.0f,  0.0f,  0.0f,-0.5f, -0.5f,  0.5f,  0.0f,  0.0f,  1.0f,  0.0f,  0.0f,0.5f, -0.5f,  0.5f,  0.0f,  0.0f,  1.0f,  1.0f,  0.0f,0.5f,  0.5f,  0.5f,  0.0f,  0.0f,  1.0f,  1.0f,  1.0f,0.5f,  0.5f,  0.5f,  0.0f,  0.0f,  1.0f,  1.0f,  1.0f,-0.5f,  0.5f,  0.5f,  0.0f,  0.0f,  1.0f,  0.0f,  1.0f,-0.5f, -0.5f,  0.5f,  0.0f,  0.0f,  1.0f,  0.0f,  0.0f,-0.5f,  0.5f,  0.5f, -1.0f,  0.0f,  0.0f,  1.0f,  0.0f,-0.5f,  0.5f, -0.5f, -1.0f,  0.0f,  0.0f,  1.0f,  1.0f,-0.5f, -0.5f, -0.5f, -1.0f,  0.0f,  0.0f,  0.0f,  1.0f,-0.5f, -0.5f, -0.5f, -1.0f,  0.0f,  0.0f,  0.0f,  1.0f,-0.5f, -0.5f,  0.5f, -1.0f,  0.0f,  0.0f,  0.0f,  0.0f,-0.5f,  0.5f,  0.5f, -1.0f,  0.0f,  0.0f,  1.0f,  0.0f,0.5f,  0.5f,  0.5f,  1.0f,  0.0f,  0.0f,  1.0f,  0.0f,0.5f,  0.5f, -0.5f,  1.0f,  0.0f,  0.0f,  1.0f,  1.0f,0.5f, -0.5f, -0.5f,  1.0f,  0.0f,  0.0f,  0.0f,  1.0f,0.5f, -0.5f, -0.5f,  1.0f,  0.0f,  0.0f,  0.0f,  1.0f,0.5f, -0.5f,  0.5f,  1.0f,  0.0f,  0.0f,  0.0f,  0.0f,0.5f,  0.5f,  0.5f,  1.0f,  0.0f,  0.0f,  1.0f,  0.0f,-0.5f, -0.5f, -0.5f,  0.0f, -1.0f,  0.0f,  0.0f,  1.0f,0.5f, -0.5f, -0.5f,  0.0f, -1.0f,  0.0f,  1.0f,  1.0f,0.5f, -0.5f,  0.5f,  0.0f, -1.0f,  0.0f,  1.0f,  0.0f,0.5f, -0.5f,  0.5f,  0.0f, -1.0f,  0.0f,  1.0f,  0.0f,-0.5f, -0.5f,  0.5f,  0.0f, -1.0f,  0.0f,  0.0f,  0.0f,-0.5f, -0.5f, -0.5f,  0.0f, -1.0f,  0.0f,  0.0f,  1.0f,-0.5f,  0.5f, -0.5f,  0.0f,  1.0f,  0.0f,  0.0f,  1.0f,0.5f,  0.5f, -0.5f,  0.0f,  1.0f,  0.0f,  1.0f,  1.0f,0.5f,  0.5f,  0.5f,  0.0f,  1.0f,  0.0f,  1.0f,  0.0f,0.5f,  0.5f,  0.5f,  0.0f,  1.0f,  0.0f,  1.0f,  0.0f,-0.5f,  0.5f,  0.5f,  0.0f,  1.0f,  0.0f,  0.0f,  0.0f,-0.5f,  0.5f, -0.5f,  0.0f,  1.0f,  0.0f,  0.0f,  1.0f};glm::vec3 position[] = {glm::vec3(0.0f, -2.0f, 0.0f),glm::vec3(0.0f, -1.0f, 0.0f),glm::vec3(0.0f, 0.0f, 0.0f),glm::vec3(-2.0f, -2.0f, 0.0f),glm::vec3(-2.0f, -1.0f, 0.0f),glm::vec3(-3.0f, -2.0f, 0.0f),glm::vec3(-2.0f, -2.0f, 1.0f),glm::vec3(-1.0f, -2.0f, -4.0f),};GLuint VBO, VAO, textureA, textureB;glGenVertexArrays(1, &VAO);glGenBuffers(1, &VBO);glBindVertexArray(VAO);glBindBuffer(GL_ARRAY_BUFFER, VBO);glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (GLvoid*)0);glEnableVertexAttribArray(0);glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));glEnableVertexAttribArray(1);glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (GLvoid*)(6 * sizeof(GLfloat)));glEnableVertexAttribArray(2);int picWidth, picHeight;glGenTextures(1, &textureA);glBindTexture(GL_TEXTURE_2D, textureA);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/wood2.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);glGenTextures(1, &textureB);glBindTexture(GL_TEXTURE_2D, textureB);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_MIPMAP_LINEAR);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST_MIPMAP_NEAREST);image = SOIL_load_image("Texture/specular.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);shaderObj.Use();glUniform1i(glGetUniformLocation(shaderObj.Program, "material.diffuse"), 0);glUniform1i(glGetUniformLocation(shaderObj.Program, "material.specular"), 1);GLuint lightVAO;glGenVertexArrays(1, &lightVAO);glBindVertexArray(lightVAO);glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * 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VBOglEnableVertexAttribArray(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();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);shaderObj.Use();glActiveTexture(GL_TEXTURE0);glBindTexture(GL_TEXTURE_2D, textureA);glActiveTexture(GL_TEXTURE1);glBindTexture(GL_TEXTURE_2D, textureB);GLint matSpecularLoc = glGetUniformLocation(shaderObj.Program, "material.specular");GLint matShineLoc = glGetUniformLocation(shaderObj.Program, "material.shininess");glUniform3f(matSpecularLoc, 0.0f, 0.0f, 0.0f);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");GLint lightK0 = glGetUniformLocation(shaderObj.Program, "light.k0");GLint lightK1 = glGetUniformLocation(shaderObj.Program, "light.k1");GLint lightK2 = glGetUniformLocation(shaderObj.Program, "light.k2");GLint lightCutOff = glGetUniformLocation(shaderObj.Program, "light.cutOff");GLint lightOutCutOff = glGetUniformLocation(shaderObj.Program, "light.outCutOff");GLint lightDirect = glGetUniformLocation(shaderObj.Program, "light.direction");glUniform3f(lightAmbientLoc, 0.2f, 0.2f, 0.2f);glUniform3f(lightDiffuseLoc, 1.0f, 1.0f, 1.0f);glUniform3f(lightSpecularLoc, 1.0f, 1.0f, 1.0f);glUniform1f(lightK0, 1.0f);glUniform1f(lightK1, 0.09f);glUniform1f(lightK2, 0.032f);glUniform3f(lightPosLoc, camera.Position.x, camera.Position.y, camera.Position.z);glUniform3f(lightDirect, camera.Front.x, camera.Front.y, camera.Front.z);glUniform1f(lightCutOff, glm::cos(glm::radians(12.5f)));glUniform1f(lightOutCutOff, glm::cos(glm::radians(15.0f)));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);for (int i = 0; i <= 7; i++){model = glm::translate(glm::mat4(1.0f), position[i]);model = glm::rotate(model, glm::radians(0.0f), glm::vec3(-0.5f, 1.0f, 0.0f));glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(model));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);
}