Framebuffer用法 Framebuffer介绍opengl中framebuffer称为帧缓冲，它是一个内存缓冲区，如果把渲染到屏幕的颜色缓冲，深度缓冲，模板缓冲都缓存到内存中，那么就叫帧缓冲。Framebuffer用法framebuffer通常用在离屏渲染或者后处理上，主要涉及这几个函数：glGenFramebuffers ：创建framebufferglBindFramebuffer ：绑定framebufferglFramebufferTexture2D ：将纹理附加到framebuffer到，实现绘制到纹理示例代码我们模拟一个后处理操作，将Blend用法中的绘制结果画在屏幕中央，并且对结果的颜色取反向，让我们看看具体代码：05.FBTexture.fs内容：#version 330 core in vec2 TexCoord; uniform sampler2D tex1; out vec4 FragColor; void main() { FragColor = vec4(vec3(1.0 - texture(tex1, TexCoord)), 1.0); }实现代码：void display( GLFWwindow* window ) { // 1.绑定framebuffer，这样可以绘制到附加的纹理fbTexture上 glBindFramebuffer(GL_FRAMEBUFFER, framebuffer); glEnable(GL_DEPTH_TEST); glEnable(GL_BLEND); glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); glClearColor( 0, 0, 0.4, 0 ); glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glUseProgram(boxProgramID); glm::mat4 projection = glm::perspective(glm::radians(45.0f), (float) 5 / (float)5, 0.1f, 100.0f); glm::mat4 view = glm::lookAt(glm::vec3(1,2,3), glm::vec3(0,0,0), glm::vec3(0,1,0)); glm::mat4 model = glm::mat4(1.0f); glm::mat4 mvp = projection * view * model; // 2.画地面 GLuint mvpId = glGetUniformLocation(boxProgramID, "MVP"); glUniformMatrix4fv(mvpId, 1, GL_FALSE, &mvp[0][0]); glBindVertexArray(FloorVAO); glBindTexture(GL_TEXTURE_2D, floorTexture); glDrawArrays(GL_TRIANGLES, 0, 6); // 3.画立方体 glBindVertexArray(VAO); glBindTexture(GL_TEXTURE_2D, texture); glDrawArrays(GL_TRIANGLES, 0, 36); // 4.画blend物体 model = glm::mat4(1.0f); model = glm::translate(model, glm::vec3(0, 0, 1.01f)); mvp = projection * view * model; glUniformMatrix4fv(mvpId, 1, GL_FALSE, &mvp[0][0]); glBindTexture(GL_TEXTURE_2D, blendTexture); glDrawArrays(GL_TRIANGLES, 0, 6); // 5.对fbTexture采样后处理将绘制到屏幕 glDisable(GL_DEPTH_TEST); glDisable(GL_BLEND); glBindFramebuffer(GL_FRAMEBUFFER, 0); glClearColor(0.3f, 0.3f, 0.3f, 1.0f); glClear(GL_COLOR_BUFFER_BIT); glUseProgram(screenProgramID); glBindVertexArray(screenVAO); glBindTexture(GL_TEXTURE_2D, fbTexture); glDrawArrays(GL_TRIANGLES, 0, 6); } void prepare() { boxProgramID = LoadShaders( "data/shader/03.MVP.vs", "data/shader/03.MVP.fs" ); const GLfloat g_vertex_buffer_data[] = { -0.5f, -0.5f, -0.5f, 0.0f, 0.0f, 0.5f, -0.5f, -0.5f, 1.0f, 0.0f, 0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 0.5f, 0.5f, -0.5f, 1.0f, 1.0f, -0.5f, 0.5f, -0.5f, 0.0f, 1.0f, -0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 0.5f, 0.5f, 0.5f, 1.0f, 1.0f, 0.5f, 0.5f, 0.5f, 1.0f, 1.0f, -0.5f, 0.5f, 0.5f, 0.0f, 1.0f, -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, -0.5f, 0.5f, 0.5f, 1.0f, 0.0f, -0.5f, 0.5f, -0.5f, 1.0f, 1.0f, -0.5f, -0.5f, -0.5f, 0.0f, 1.0f, -0.5f, -0.5f, -0.5f, 0.0f, 1.0f, -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, -0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 0.5f, -0.5f, -0.5f, 0.0f, 1.0f, 0.5f, -0.5f, -0.5f, 0.0f, 1.0f, 0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 0.5f, 0.5f, 0.5f, 1.0f, 0.0f, -0.5f, -0.5f, -0.5f, 0.0f, 1.0f, 0.5f, -0.5f, -0.5f, 1.0f, 1.0f, 0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 0.5f, -0.5f, 0.5f, 1.0f, 0.0f, -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, -0.5f, -0.5f, -0.5f, 0.0f, 1.0f, -0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.5f, 0.5f, 0.5f, 1.0f, 0.0f, -0.5f, 0.5f, 0.5f, 0.0f, 0.0f, -0.5f, 0.5f, -0.5f, 0.0f, 1.0f }; float fllor_vertex_buffer_data[] = { 5.0f, -0.5f, 5.0f, 1.0f, 0.0f, -5.0f, -0.5f, 5.0f, 0.0f, 0.0f, -5.0f, -0.5f, -5.0f, 0.0f, 1.0f, 5.0f, -0.5f, 5.0f, 1.0f, 0.0f, -5.0f, -0.5f, -5.0f, 0.0f, 1.0f, 5.0f, -0.5f, -5.0f, 1.0f, 1.0f }; float blend_vertex_buffer_data[] = { 0.0f, 0.5f, 0.0f, 0.0f, 0.0f, 0.0f, -0.5f, 0.0f, 0.0f, 1.0f, 1.0f, -0.5f, 0.0f, 1.0f, 1.0f, 0.0f, 0.5f, 0.0f, 0.0f, 0.0f, 1.0f, -0.5f, 0.0f, 1.0f, 1.0f, 1.0f, 0.5f, 0.0f, 1.0f, 0.0f }; // 1.VAO、VBO的数据 glGenVertexArrays(1, &VAO); glBindVertexArray(VAO); GLuint VBO1; glGenBuffers(1, &VBO1); glBindBuffer(GL_ARRAY_BUFFER, VBO1); glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)0); // 纹理坐标 glEnableVertexAttribArray(1); glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat))); // 2.地面贴图 glGenVertexArrays(1, &FloorVAO); glBindVertexArray(FloorVAO); GLuint VBO2; glGenBuffers(1, &VBO2); glBindBuffer(GL_ARRAY_BUFFER, VBO2); glBufferData(GL_ARRAY_BUFFER, sizeof(fllor_vertex_buffer_data), fllor_vertex_buffer_data, GL_STATIC_DRAW); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)0); // 纹理坐标 glEnableVertexAttribArray(1); glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat))); // 3.blend贴图 glGenVertexArrays(1, &BlendVAO); glBindVertexArray(BlendVAO); GLuint VBO3; glGenBuffers(1, &VBO3); glBindBuffer(GL_ARRAY_BUFFER, VBO3); glBufferData(GL_ARRAY_BUFFER, sizeof(blend_vertex_buffer_data), blend_vertex_buffer_data, GL_STATIC_DRAW); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)0); // 纹理坐标 glEnableVertexAttribArray(1); glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat))); // 纹理数据 floorTexture = loadTexture("data/img/33.png"); texture = loadTexture("data/img/11.jpg"); blendTexture = loadTexture("data/img/chick.png"); // 4.创建framebuffer以及附加的纹理 glGenFramebuffers(1, &framebuffer); glBindFramebuffer(GL_FRAMEBUFFER, framebuffer); glGenTextures(1, &fbTexture); glBindTexture(GL_TEXTURE_2D, fbTexture); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 512, 512, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, fbTexture, 0); // 5.绘制到屏幕的shader和顶点数据 screenProgramID = LoadShaders( "data/shader/02.Texture.vs", "data/shader/05.FBTexture.fs" ); const GLfloat g_screen_vertex_buffer_data[] = { -0.5f, 0.5f, 0.0f, 0.0f, 1.0f, -0.5f, -0.5f, 0.0f, 0.0f, 0.0f, 0.5f, -0.5f, 0.0f, 1.0f, 0.0f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 0.5f, 0.5f, 0.0f, 1.0f, 1.0f }; // VAO、VBO的数据 GLuint screenVBO; glGenVertexArrays(1, &screenVAO); glBindVertexArray(screenVAO); glGenBuffers(1, &screenVBO); glBindBuffer(GL_ARRAY_BUFFER, screenVBO); glBufferData(GL_ARRAY_BUFFER, sizeof(g_screen_vertex_buffer_data), g_screen_vertex_buffer_data, GL_STATIC_DRAW); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)0); glEnableVertexAttribArray(1); glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat))); }最终显示结果：

Blend用法 Blend用法opengl的blend用于颜色混合 ，如果不用混合，两张贴图贴在一起时，前面的贴图会覆盖后面的贴图，加上混合功能，两张贴图可以很好的贴合在一起。用代码演示一下用法。blend开启方法blend主要使用下面几个函数：glEnable(GL_BLEND): 开启blend功能glBlendFunc(GLenum sfactor, GLenum dfactor): sfactor源因子，dfactor目标因子示例代码我们先画一个普通场景void display( GLFWwindow* window ) { glClearColor( 0, 0, 0.4, 0 ); glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glUseProgram(boxProgramID); glm::mat4 projection = glm::perspective(glm::radians(45.0f), (float) 5 / (float)5, 0.1f, 100.0f); glm::mat4 view = glm::lookAt(glm::vec3(1,2,3), glm::vec3(0,0,0), glm::vec3(0,1,0)); glm::mat4 model = glm::mat4(1.0f); glm::mat4 mvp = projection * view * model; // 1.画地面 GLuint mvpId = glGetUniformLocation(boxProgramID, "MVP"); glUniformMatrix4fv(mvpId, 1, GL_FALSE, &mvp[0][0]); glBindVertexArray(FloorVAO); glBindTexture(GL_TEXTURE_2D, floorTexture); glDrawArrays(GL_TRIANGLES, 0, 6); // 2.画立方体 glBindVertexArray(VAO); glBindTexture(GL_TEXTURE_2D, texture); glDrawArrays(GL_TRIANGLES, 0, 36); // 3.画blend物体 model = glm::mat4(1.0f); model = glm::translate(model, glm::vec3(0, 0, 1.01f)); mvp = projection * view * model; glUniformMatrix4fv(mvpId, 1, GL_FALSE, &mvp[0][0]); glBindTexture(GL_TEXTURE_2D, blendTexture); glDrawArrays(GL_TRIANGLES, 0, 6); } void prepare() { boxProgramID = LoadShaders( "data/shader/03.MVP.vs", "data/shader/03.MVP.fs" ); const GLfloat g_vertex_buffer_data[] = { -0.5f, -0.5f, -0.5f, 0.0f, 0.0f, 0.5f, -0.5f, -0.5f, 1.0f, 0.0f, 0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 0.5f, 0.5f, -0.5f, 1.0f, 1.0f, -0.5f, 0.5f, -0.5f, 0.0f, 1.0f, -0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 0.5f, 0.5f, 0.5f, 1.0f, 1.0f, 0.5f, 0.5f, 0.5f, 1.0f, 1.0f, -0.5f, 0.5f, 0.5f, 0.0f, 1.0f, -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, -0.5f, 0.5f, 0.5f, 1.0f, 0.0f, -0.5f, 0.5f, -0.5f, 1.0f, 1.0f, -0.5f, -0.5f, -0.5f, 0.0f, 1.0f, -0.5f, -0.5f, -0.5f, 0.0f, 1.0f, -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, -0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 0.5f, -0.5f, -0.5f, 0.0f, 1.0f, 0.5f, -0.5f, -0.5f, 0.0f, 1.0f, 0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 0.5f, 0.5f, 0.5f, 1.0f, 0.0f, -0.5f, -0.5f, -0.5f, 0.0f, 1.0f, 0.5f, -0.5f, -0.5f, 1.0f, 1.0f, 0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 0.5f, -0.5f, 0.5f, 1.0f, 0.0f, -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, -0.5f, -0.5f, -0.5f, 0.0f, 1.0f, -0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.5f, 0.5f, 0.5f, 1.0f, 0.0f, -0.5f, 0.5f, 0.5f, 0.0f, 0.0f, -0.5f, 0.5f, -0.5f, 0.0f, 1.0f }; float fllor_vertex_buffer_data[] = { 5.0f, -0.5f, 5.0f, 1.0f, 0.0f, -5.0f, -0.5f, 5.0f, 0.0f, 0.0f, -5.0f, -0.5f, -5.0f, 0.0f, 1.0f, 5.0f, -0.5f, 5.0f, 1.0f, 0.0f, -5.0f, -0.5f, -5.0f, 0.0f, 1.0f, 5.0f, -0.5f, -5.0f, 1.0f, 1.0f }; float blend_vertex_buffer_data[] = { 0.0f, 0.5f, 0.0f, 0.0f, 0.0f, 0.0f, -0.5f, 0.0f, 0.0f, 1.0f, 1.0f, -0.5f, 0.0f, 1.0f, 1.0f, 0.0f, 0.5f, 0.0f, 0.0f, 0.0f, 1.0f, -0.5f, 0.0f, 1.0f, 1.0f, 1.0f, 0.5f, 0.0f, 1.0f, 0.0f }; // 1.VAO1、VBO的数据 glGenVertexArrays(1, &VAO); glBindVertexArray(VAO); GLuint VBO1; glGenBuffers(1, &VBO1); glBindBuffer(GL_ARRAY_BUFFER, VBO1); glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)0); // 纹理坐标 glEnableVertexAttribArray(1); glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat))); // 2.地面贴图 glGenVertexArrays(1, &FloorVAO); glBindVertexArray(FloorVAO); GLuint VBO2; glGenBuffers(1, &VBO2); glBindBuffer(GL_ARRAY_BUFFER, VBO2); glBufferData(GL_ARRAY_BUFFER, sizeof(fllor_vertex_buffer_data), fllor_vertex_buffer_data, GL_STATIC_DRAW); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)0); // 纹理坐标 glEnableVertexAttribArray(1); glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat))); // 2.blend贴图 glGenVertexArrays(1, &BlendVAO); glBindVertexArray(BlendVAO); GLuint VBO3; glGenBuffers(1, &VBO3); glBindBuffer(GL_ARRAY_BUFFER, VBO3); glBufferData(GL_ARRAY_BUFFER, sizeof(blend_vertex_buffer_data), blend_vertex_buffer_data, GL_STATIC_DRAW); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)0); // 纹理坐标 glEnableVertexAttribArray(1); glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat))); // 纹理数据 floorTexture = loadTexture("data/img/33.png"); texture = loadTexture("data/img/11.jpg"); blendTexture = loadTexture("data/img/chick.png"); glEnable(GL_DEPTH_TEST); }都是普通贴图操作，显示效果如下：因为是直接贴图覆盖的，所以小鸡周边alpha为0的颜色显示为黑色，如果加上blend功能，则可以看到后面图片的内容了：glEnable(GL_BLEND); glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);最终显示效果：

Stencil用法 模板测试opengl的stencil称为模板测试，和深度测试一样，是Opengl中常用的技术。概念就不解释了，直接演示用法。我们实现对一个立方体盒子进行高亮描边。stencil用法stencil最简单的用法是使用下面三个函数：glStencilMask(GLuint value): 位遮罩， 0x00设置模板缓冲不可写入；value=0xFF设置可以写入。glStencilFunc(GLenum func, GLint ref, GLuint mask): 用ref值与存储的模板值比较，func为比较方法。glStencilOp(GLenum sfail, GLenum dpfail, GLenum dppass): 模板值的写入策略简单来说，glStencilMask是开关，开了才可以写入模板值；glStencilFunc是写入模板值的前提条件；glStencilOp是模板值的具体写入方法。示例代码普通流程我们先准备好了画一个立方体盒子的代码：GLuint boxProgramID; void display( GLFWwindow* window ) { glClearColor( 0, 0, 0.4, 0 ); glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // 设置好坐标变化的mvp glm::mat4 projection = glm::perspective(glm::radians(45.0f), (float) 5 / (float)5, 0.1f, 100.0f); glm::mat4 view = glm::lookAt(glm::vec3(1,2,3), glm::vec3(0,0,0), glm::vec3(0,1,0)); glm::mat4 model = glm::mat4(1.0f); glm::mat4 mvp = projection * view * model; // 画立方体 glUseProgram(boxProgramID); GLuint mvpId = glGetUniformLocation(boxProgramID, "MVP"); glUniformMatrix4fv(mvpId, 1, GL_FALSE, &mvp[0][0]); glDrawArrays(GL_TRIANGLES, 0, 36); } void prepare() { boxProgramID = LoadShaders( "data/shader/03.MVP.vs", "data/shader/03.MVP.fs" ); // 立方体的顶点坐标，纹理坐标 const GLfloat g_vertex_buffer_data[] = { -0.5f, -0.5f, -0.5f, 0.0f, 0.0f, 0.5f, -0.5f, -0.5f, 1.0f, 0.0f, 0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 0.5f, 0.5f, -0.5f, 1.0f, 1.0f, -0.5f, 0.5f, -0.5f, 0.0f, 1.0f, -0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 0.5f, 0.5f, 0.5f, 1.0f, 1.0f, 0.5f, 0.5f, 0.5f, 1.0f, 1.0f, -0.5f, 0.5f, 0.5f, 0.0f, 1.0f, -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, -0.5f, 0.5f, 0.5f, 1.0f, 0.0f, -0.5f, 0.5f, -0.5f, 1.0f, 1.0f, -0.5f, -0.5f, -0.5f, 0.0f, 1.0f, -0.5f, -0.5f, -0.5f, 0.0f, 1.0f, -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, -0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 0.5f, -0.5f, -0.5f, 0.0f, 1.0f, 0.5f, -0.5f, -0.5f, 0.0f, 1.0f, 0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 0.5f, 0.5f, 0.5f, 1.0f, 0.0f, -0.5f, -0.5f, -0.5f, 0.0f, 1.0f, 0.5f, -0.5f, -0.5f, 1.0f, 1.0f, 0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 0.5f, -0.5f, 0.5f, 1.0f, 0.0f, -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, -0.5f, -0.5f, -0.5f, 0.0f, 1.0f, -0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.5f, 0.5f, 0.5f, 1.0f, 0.0f, -0.5f, 0.5f, 0.5f, 0.0f, 0.0f, -0.5f, 0.5f, -0.5f, 0.0f, 1.0f }; // VAO、VBO的数据 GLuint VAO1; GLuint VBO1; glGenVertexArrays(1, &VAO1); glBindVertexArray(VAO1); glGenBuffers(1, &VBO1); glBindBuffer(GL_ARRAY_BUFFER, VBO1); glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)0); // 纹理数据 GLuint texture; glGenTextures(1, &texture); glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture); // 环绕方式 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); // 过滤方式 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); // 加载图片数据 int width, height, channels; stbi_set_flip_vertically_on_load(true); unsigned char* data = stbi_load("data/img/test.jpg", &width, &height, &channels, 0); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data); stbi_image_free(data); // 纹理坐标 glEnableVertexAttribArray(1); glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat))); glEnable(GL_DEPTH_TEST); } int main( int argc, char** argv ) { glfwInit(); GLFWwindow* window = glfwCreateWindow( 512, 512, "OpenGL_Tutorial", NULL, NULL ); glfwMakeContextCurrent( window ); gladLoadGLLoader( (GLADloadproc)glfwGetProcAddress ); glfwSwapInterval( 1 ); glfwSetKeyCallback( window, keyboard ); glfwSetCursorPosCallback( window, motion ); glfwSetMouseButtonCallback( window, mouse ); prepare(); while (!glfwWindowShouldClose(window)) { display(window); glfwPollEvents(); glfwSwapBuffers(window); } glfwTerminate(); return 0; }显示效果如图：使用模板测试功能加入模板测试功能，流程描述：开启模板测试清除所有模板值画一个立方体盒子，将盒子区域的模板值设置可写，值为1画一个稍大点的盒子(盒子放大1.05倍)，不贴图，fs里直接设置颜色固定值，进行模板测试，模板测试条件为模板值 != 1，设置模板值不可写。具体代码：void display( GLFWwindow* window ) { // 1.开启stencil功能 glEnable(GL_STENCIL_TEST); // 设置模板值可写，下面的clear GL_STENCIL_BUFFER_BIT操作才能执行 glStencilMask(0xFF); // 设置模板测试成功的写入方式为替换，即测试成功，使用glStencilFunc中的ref值写入模板值 glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE); glClearColor( 0, 0, 0.4, 0 ); // 2.清除深度、模板值 glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT); // 3.画立方体 glm::mat4 projection = glm::perspective(glm::radians(45.0f), (float) 5 / (float)5, 0.1f, 100.0f); glm::mat4 view = glm::lookAt(glm::vec3(1,2,3), glm::vec3(0,0,0), glm::vec3(0,1,0)); glm::mat4 model = glm::mat4(1.0f); glm::mat4 mvp = projection * view * model; // 设置模板值的写入策略，GL_ALWAYS表示无条件写入 glStencilFunc(GL_ALWAYS, 1, 0xFF); glUseProgram(boxProgramID); GLuint mvpId = glGetUniformLocation(boxProgramID, "MVP"); glUniformMatrix4fv(mvpId, 1, GL_FALSE, &mvp[0][0]); glDrawArrays(GL_TRIANGLES, 0, 36); // 4.画描边 model = glm::mat4(1.0f); // 放大盒子为原来的1.05倍 model = glm::scale(model, glm::vec3(1.05, 1.05, 1.05)); mvp = projection * view * model; // 进行模板测试，只有不等于1的模板值才测试成功 glStencilFunc(GL_NOTEQUAL, 1, 0xFF); // 设置模板值不可写，此处无需更新模板值 glStencilMask(0x00); glUseProgram(stencilProgramID); mvpId = glGetUniformLocation(stencilProgramID, "MVP"); glUniformMatrix4fv(mvpId, 1, GL_FALSE, &mvp[0][0]); glDrawArrays(GL_TRIANGLES, 0, 36); }现在的效果：

MVP变换坐标 MVP概念在opengl中，MVP称为模型观察投影矩阵，它是模型（Model）、观察（View）和投影（Projection）矩阵作用在物体上组合作用，用于对物体的坐标系进行变换。如上图所示，物体的坐标系变化过程为：局部坐标系世界坐标系观察坐标系裁剪坐标系MVP公式$$ MVP=Mprojection⋅Mview⋅Mmodel$$在shader中用MVP * gl_Position 得到转换后的坐标。示例代码在OpenGL纹理中，介绍了纹理的使用方法，最终的运行效果为：修改vertext shader，添加MVP变量#version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec2 aTexCoord; uniform mat4 MVP; out vec2 TexCoord; void main() { gl_Position = MVP * vec4(aPos, 1.0); TexCoord = aTexCoord; }在绘制之前将MVP矩阵传入着色器：glm::mat4 projection = glm::perspective(glm::radians(45.0f), (float) width / (float)height, 0.1f, 100.0f); glm::mat4 view = glm::lookAt(glm::vec3(1,2,3), glm::vec3(0,0,0), glm::vec3(0,1,0)); glm::mat4 model = glm::mat4(1.0f); glm::mat4 mvp = projection * view * model; GLuint mvpId = glGetUniformLocation(programID, "MVP"); glUniformMatrix4fv(mvpId, 1, GL_FALSE, &mvp[0][0]);现在的运行效果如下：

OpenGL纹理 简介opengl纹理简单来说就是贴图，像2D游戏，就是用大量的贴图拼起来组成丰富多彩的画面。下面我们详细地描述一下使用纹理的代码方式。示例代码顶点着色器输入两组坐标，顶点坐标和纹理坐标，纹理坐标直接传递给片段着色器//02.Texture.vs #version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec2 aTexCoord; out vec2 TexCoord; void main() { gl_Position = vec4(aPos, 1.0); TexCoord = aTexCoord; }片段着色器定义一个纹理采样器text1，它与代码中绑定的TEXTURE0关联，使用传入的纹理坐标采样//02.Texture.fs #version 330 core in vec2 TexCoord; uniform sampler2D tex1; out vec4 FragColor; void main() { FragColor = texture(tex1, TexCoord); }实现代码逻辑GLuint programID = LoadShaders( "data/shader/02.Texture.vs", "data/shader/02.Texture.fs" ); glUseProgram(programID); // 顶点、纹理坐标 const GLfloat g_vertex_buffer_data[] = { -0.5f, -0.5f, 0.0f, 0.0f, 0.0f, // 左下角 0.5f, -0.5f, 0.0f, 1.0f, 0.0f, // 右下角 -0.5f, 0.5f, 0.0f, 0.0f, 1.0f, // 左上角 0.5f, 0.5f, 0.0f, 1.0f, 1.0f // 右上角 }; // 顶点索引 unsigned int indices[] = {0, 1, 2, 1, 2, 3}; // VAO1、VBO1、EBO1的数据 GLuint VAO1; GLuint VBO1; GLuint EBO1; glGenVertexArrays(1, &VAO1); glBindVertexArray(VAO1); glGenBuffers(1, &VBO1); glBindBuffer(GL_ARRAY_BUFFER, VBO1); glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW); glGenBuffers(1, &EBO1); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO1); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)0); // 纹理数据 GLuint texture; glGenTextures(1, &texture); glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture); // 环绕方式 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); // 过滤方式 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); // 加载图片数据 int width, height, channels; // 图像坐标系与纹理坐标系相反，翻转y轴 stbi_set_flip_vertically_on_load(true); unsigned char* data = stbi_load("data/img/test.jpg", &width, &height, &channels, 0); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data); stbi_image_free(data); // 纹理坐标 glEnableVertexAttribArray(1); glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat)));运行效果：环绕方式通过设置GL_TEXTURE_WRAP_参数来设置环绕方式GL_REPEAT: 超出纹理范围的坐标整数部分被忽略，形成重复效果。GL_MIRRORED_REPEAT: 超出纹理范围的坐标整数部分被忽略，但当整数部分为奇数时进行取反，形成镜像效果。GL_CLAMP_TO_EDGE: 超出纹理范围的坐标被截取成0和1，形成纹理边缘延伸的效果。GL_CLAMP_TO_BORDER: 超出纹理范围的部分被设置为边缘色。如果将纹理坐标改成如下:const GLfloat g_vertex_buffer_data[] = { -0.5f, -0.5f, 0.0f, 0.0f, 0.0f, // 左下角 0.5f, -0.5f, 0.0f, 2.0f, 0.0f, // 右下角 -0.5f, 0.5f, 0.0f, 0.0f, 2.0f, // 左上角 0.5f, 0.5f, 0.0f, 2.0f, 2.0f // 右上角 };不同环绕方式对应的效果:GL_REPEATGL_MIRRORED_REPEATGL_CLAMP_TO_EDGEGL_CLAMP_TO_BORDER