OpenGL基础22：贴图
在 OpenGL基础13：第一个正方体 中给正方体加了箱子的纹理，但是在后面介绍光照的时候又把纹理属性给丢了，现在尝试在有纹理的基础之上增加光照
一、漫反射贴图
先把之前的纹理加回去
顶点着色器和主代码的处理和之前 OpenGL基础9：纹理 纹理这一章一样，而对于片段着色器，需要进行稍加修改
在 OpenGL基础21：材质 这一章里，给予了物体材质属性，包括：
- ambient：定义了在环境光照下这个物体反射的是什么颜色，通常是和物体颜色相同的颜色
- diffuse：定义了在漫反射光照下物体的颜色，通常是和物体颜色相同的颜色
- specular：
设置的是物体受到的镜面光照影响的颜色，或者是反射一个物体特定的镜面高光颜色（暂时不考虑） - shininess：
反光度，值越高，反射光的能力越强，散射得越少，高光点越小（暂时不考虑）
但是，一个物体自身作为一个整体为其拥有一个材质其实是有问题的，例如一辆汽车，轮胎和车窗的材质明显不同，也就是说，对于物体的不同部分，可能会拥有不同的 ambient 和 diffuse 属性
因此，这就需要通过某种方式对每个原始像素独立设置diffuse颜色，这其实就是之前的一直在用的纹理，只不过在这中场景和需求下，我们叫它贴图
用一张图片覆盖住物体，以便我们为每个原始像素索引独立颜色值。在光照场景中，通过纹理来呈现一个物体的diffuse颜色，这个做法被称做漫反射贴图(Diffuse texture)
这样的话，在片段着色器中，原先的 ambient 和 diffuse 属性就要用 diffuse 贴图替代（之所以这两个属性都用 diffuse 是因为大部分情况下，这两者的值是等同的），如下：
#version 330 core
struct Material
{
sampler2D diffuse; //贴图
vec3 specular; //镜面光色
float shininess; //反光度
};
struct Light
{
vec3 position;
vec3 ambient;
vec3 diffuse;
vec3 specular;
};
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));
//漫反射光
vec3 norm = normalize(normalIn);
vec3 lightDir = normalize(light.position - fragPosIn);
float diff = max(dot(norm, lightDir), 0.0f);
vec3 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);
vec3 specular = light.specular * (spec * material.specular);
//混合
vec3 result = ambient + diffuse + specular;
color = vec4(result, 1.0f);
}好了，效果有了！
如果仔细从各个角度看，会发现一块木箱子居然还会有镜面高光，这不科学，这时可以把 specular 设置为 vec(0.0) 来修正
二、镜面贴图采样
上面的箱子还是非常容易的，因为它有一个特点：每个部分都拥有几乎一致的 diffuse 属性，并且 specular 属性都为 vec(0.0)，那么问题来了，假设这个时候我们想要给箱子加一个金属边框要怎么处理？要知道金属拥有较高的反射度，和橡木材质正好相反，如果说只用单独的一个带金属边框的木箱纹理，那肯定也是有问题的，所以这个时候就需要2张纹理贴图：一张为带金属边框的橡木纹理，一张为单纯金属边框纹理
如下，一个 specular 高光的亮度可以通过图片中每个纹理的亮度来获得，可以使用这两张纹理作为漫反射贴图和镜面贴图（来源：https://learnopengl.com/#!Lighting/Lighting-maps）
specular 贴图的每个像素可以显示为一个颜色向量，可以看出，这张纹理中间是一片黑，这也意味着中间部分是露出来的木头材质，在此 specular 属性即对应像素颜色属性正是 vec(0.0)
使用Photoshop或Gimp之类的工具，通过将图片进行裁剪，将某部分调整成黑白图样，并调整亮度/对比度的做法，可以非常容易将一个diffuse纹理贴图处理为specular贴图，这样的贴图最好为黑白
有了上面的经验，就知道怎么修改代码逻辑了：
#version 330 core
struct Material
{
sampler2D diffuse; //贴图
sampler2D specular; //镜面贴图
float shininess; //反光度
};
struct Light
{
vec3 position;
vec3 ambient;
vec3 diffuse;
vec3 specular;
};
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));
//漫反射光
vec3 norm = normalize(normalIn);
vec3 lightDir = normalize(light.position - fragPosIn);
float diff = max(dot(norm, lightDir), 0.0f);
vec3 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);
vec3 specular = light.specular * (spec * vec3(texture(material.specular, texIn)));
//混合
vec3 result = ambient + diffuse + specular;
color = vec4(result, 1.0f);
}效果如下：
三、放射光贴图
上面使用了漫反射贴图和镜面贴图，物体已经有点真实的感觉了，后面还有法线贴图和反射贴图，可以给物体更完美的细节，只是这里就暂时不讲了
这里可以再提一个非常简单的贴图：放射光贴图，先上整篇文章的完整代码和效果，非常容易
#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 ambient;
vec3 diffuse;
vec3 specular;
};
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));
//漫反射光
vec3 norm = normalize(normalIn);
vec3 lightDir = normalize(light.position - fragPosIn);
float diff = max(dot(norm, lightDir), 0.0f);
vec3 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);
vec3 specular = light.specular * (spec * vec3(texture(material.specular, texIn)));
//放射光贴图
vec3 emission = vec3(texture(material.emission, texIn));
//混合
vec3 result = ambient + diffuse + specular + emission;
color = vec4(result, 1.0f);
}main.cpp：
#include
#include
#define GLEW_STATIC
#include
#include"Camera.h"
#include
#include
#include
#include"Shader.h"
#include
#include
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
};
GLuint VBO, VAO, textureA, textureB, textureC;
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);
glGenTextures(1, &textureC);
glBindTexture(GL_TEXTURE_2D, textureC);
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/cloudImg.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);
glUniform1i(glGetUniformLocation(shaderObj.Program, "material.emission"), 2);
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VBO
glEnableVertexAttribArray(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);
glActiveTexture(GL_TEXTURE2);
glBindTexture(GL_TEXTURE_2D, textureC);
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");
glUniform3f(lightAmbientLoc, 0.2f, 0.2f, 0.2f);
glUniform3f(lightDiffuseLoc, 1.0f, 1.0f, 1.0f);
glUniform3f(lightSpecularLoc, 1.0f, 1.0f, 1.0f);
glUniform3f(lightPosLoc, lightPos.x, lightPos.y, lightPos.z);
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);
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);
} 
可以看到，箱子的每个面上都有被贴上了一块无视光照的“云彩”，这就是放射光贴图，顾名思义，它往往是用来显示物体自身发光(Emit)时可能产生的颜色，例如游戏中宝箱上发光的按钮，楼梯间紧急出口牌子亮的绿光等等