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2024-06-29 20:21| 来源: 网络整理| 查看: 265

主要介绍Visual studio 2019 OpenGL纹理图片加载方法，包括纹理坐标、bmp格式纹理图片载入函数、OpenGL中纹理的设置等内容

视频讲解：【2.5.1 Visual Studio OpenGL 之纹理立方体-哔哩哔哩】 https://b23.tv/tAKUFaU

OpenGL官方教程网: Tutorial 5 : A Textured Cube (opengl-tutorial.org)

.cpp主程序

#include #include #include #include #include #include #include #include using namespace glm; GLuint loadBMP_custom(const char* imagepath); unsigned char* data; unsigned int width, height; // A cube has 6 faces with 2 triangles each, so this makes 6*2=12 triangles, and 12*3 vertices static const GLfloat g_vertex_buffer_data[] = { -1.0f,-1.0f,-1.0f, // triangle 1 : begin -1.0f,-1.0f, 1.0f, -1.0f, 1.0f, 1.0f, // triangle 1 : end 1.0f, 1.0f,-1.0f, // triangle 2 : begin -1.0f,-1.0f,-1.0f, -1.0f, 1.0f,-1.0f, // triangle 2 : end 1.0f,-1.0f, 1.0f, -1.0f,-1.0f,-1.0f, 1.0f,-1.0f,-1.0f, 1.0f, 1.0f,-1.0f, 1.0f,-1.0f,-1.0f, -1.0f,-1.0f,-1.0f, -1.0f,-1.0f,-1.0f, -1.0f, 1.0f, 1.0f, -1.0f, 1.0f,-1.0f, 1.0f,-1.0f, 1.0f, -1.0f,-1.0f, 1.0f, -1.0f,-1.0f,-1.0f, -1.0f, 1.0f, 1.0f, -1.0f,-1.0f, 1.0f, 1.0f,-1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,-1.0f,-1.0f, 1.0f, 1.0f,-1.0f, 1.0f,-1.0f,-1.0f, 1.0f, 1.0f, 1.0f, 1.0f,-1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,-1.0f, -1.0f, 1.0f,-1.0f, 1.0f, 1.0f, 1.0f, -1.0f, 1.0f,-1.0f, -1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, -1.0f, 1.0f, 1.0f, 1.0f,-1.0f, 1.0f }; // Two UV coordinatesfor each vertex. They were created with Blender. You'll learn shortly how to do this yourself. static const GLfloat g_uv_buffer_data[] = { 0.000059f, 1.0f - 0.000004f, 0.000103f, 1.0f - 0.336048f, 0.335973f, 1.0f - 0.335903f, 1.000023f, 1.0f - 0.000013f, 0.667979f, 1.0f - 0.335851f, 0.999958f, 1.0f - 0.336064f, 0.667979f, 1.0f - 0.335851f, 0.336024f, 1.0f - 0.671877f, 0.667969f, 1.0f - 0.671889f, 1.000023f, 1.0f - 0.000013f, 0.668104f, 1.0f - 0.000013f, 0.667979f, 1.0f - 0.335851f, 0.000059f, 1.0f - 0.000004f, 0.335973f, 1.0f - 0.335903f, 0.336098f, 1.0f - 0.000071f, 0.667979f, 1.0f - 0.335851f, 0.335973f, 1.0f - 0.335903f, 0.336024f, 1.0f - 0.671877f, 1.000004f, 1.0f - 0.671847f, 0.999958f, 1.0f - 0.336064f, 0.667979f, 1.0f - 0.335851f, 0.668104f, 1.0f - 0.000013f, 0.335973f, 1.0f - 0.335903f, 0.667979f, 1.0f - 0.335851f, 0.335973f, 1.0f - 0.335903f, 0.668104f, 1.0f - 0.000013f, 0.336098f, 1.0f - 0.000071f, 0.000103f, 1.0f - 0.336048f, 0.000004f, 1.0f - 0.671870f, 0.336024f, 1.0f - 0.671877f, 0.000103f, 1.0f - 0.336048f, 0.336024f, 1.0f - 0.671877f, 0.335973f, 1.0f - 0.335903f, 0.667969f, 1.0f - 0.671889f, 1.000004f, 1.0f - 0.671847f, 0.667979f, 1.0f - 0.335851f }; GLuint Texture = loadBMP_custom("uvtemplate.bmp"); int main() { // Initialise GLFW glewExperimental = true; // Needed for core profile if (!glfwInit()) { fprintf(stderr, "Failed to initialize GLFW\n"); return -1; } glfwWindowHint(GLFW_SAMPLES, 4); // 4x antialiasing glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); // We want OpenGL 3.3 glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3); glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // To make MacOS happy; should not be needed glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); // We don't want the old OpenGL // Open a window and create its OpenGL context GLFWwindow* window; // (In the accompanying source code, this variable is global for simplicity) window = glfwCreateWindow(1024, 768, "Tutorial 01", NULL, NULL); if (window == NULL) { fprintf(stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.\n"); glfwTerminate(); return -1; } glfwMakeContextCurrent(window); // Initialize GLEW glewExperimental = true; // Needed in core profile if (glewInit() != GLEW_OK) { fprintf(stderr, "Failed to initialize GLEW\n"); return -1; } /****************Tutorial 4 Matrix***********************************/ // Projection matrix : 45° Field of View, 4:3 ratio, display range : 0.1 unit 100 units glm::mat4 Projection = glm::perspective(glm::radians(45.0f), (float)4 / (float)3, 0.1f, 100.0f); // Or, for an ortho camera : //glm::mat4 Projection = glm::ortho(-10.0f,10.0f,-10.0f,10.0f,0.0f,100.0f); // In world coordinates // Camera matrix glm::mat4 View = glm::lookAt( glm::vec3(4, 3, -3), // Camera is at (4,3,-3), in World Space glm::vec3(0, 0, 0), // and looks at the origin glm::vec3(0, 1, 0) // Head is up (set to 0,-1,0 to look upside-down) ); // Model matrix : an identity matrix (model will be at the origin) glm::mat4 Model = glm::mat4(1.0f); // Our ModelViewProjection : multiplication of our 3 matrices glm::mat4 mvp = Projection * View * Model; // Remember, matrix multiplication is the other way around /****************Tutorial 2 The first triangle***********************************/ GLuint VertexArrayID; glGenVertexArrays(1, &VertexArrayID); glBindVertexArray(VertexArrayID); // This will identify our vertex buffer GLuint vertexbuffer; glGenBuffers(1, &vertexbuffer);// Generate 1 buffer, put the resulting identifier in vertexbuffer glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer); // The following commands will talk about our 'vertexbuffer' buffer glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW); // Give our vertices to OpenGL. /****************Tutorial 5 texture*****************************/ // Create one OpenGL texture GLuint textureID; glGenTextures(1, &textureID); // "Bind" the newly created texture : all future texture functions will modify this texture glBindTexture(GL_TEXTURE_2D, textureID); // Give the image to OpenGL glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_BGR, GL_UNSIGNED_BYTE, data); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); // When MAGnifying the image (no bigger mipmap available), use LINEAR filtering /* glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); // When MINifying the image, use a LINEAR blend of two mipmaps, each filtered LINEARLY too glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); // Generate mipmaps, by the way. glGenerateMipmap(GL_TEXTURE_2D); */ // Create and compile our GLSL program from the shaders GLuint programID = LoadShaders("SimpleVertexShader.vertexshader", "SimpleFragmentShader.fragmentshader"); GLuint MatrixID = glGetUniformLocation(programID, "MVP"); glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE); do { // Clear the screen. It's not mentioned before Tutorial 02, but it can cause flickering, so it's there nonetheless. glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnable(GL_DEPTH_TEST);// Enable depth test glDepthFunc(GL_LESS);// Accept fragment if it closer to the camera than the former one glUseProgram(programID);// Use our shader // 1st attribute buffer : vertices glEnableVertexAttribArray(0); glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer); glVertexAttribPointer( 0, // attribute 0. No particular reason for 0, but must match the layout in the shader. 3, // size GL_FLOAT, // type GL_FALSE, // normalized? 0, // stride (void*)0 // array buffer offset ); // 2nd attribute buffer : TEXTURE glEnableVertexAttribArray(1); glBindBuffer(GL_ARRAY_BUFFER, textureID );//colorbuffer glVertexAttribPointer( 1, // attribute. No particular reason for 1, but must match the layout in the shader. 2, // size GL_FLOAT, // type GL_FALSE, // normalized? 0, // stride (void*)0 // array buffer offset ); glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &mvp[0][0]);// Send our transformation to the currently bound shader, in the "MVP" uniform glDrawArrays(GL_TRIANGLES, 0, 3*12); // Starting from vertex 0; 3 vertices total -> 1 triangle glDisableVertexAttribArray(0); glDisableVertexAttribArray(1); glfwSwapBuffers(window);// Swap buffers glfwPollEvents(); } // Check if the ESC key was pressed or the window was closed while (glfwGetKey(window, GLFW_KEY_ESCAPE) != GLFW_PRESS && glfwWindowShouldClose(window) == 0); } GLuint loadBMP_custom(const char* imagepath){ // Data read from the header of the BMP file unsigned char header[54]; // Each BMP file begins by a 54-bytes header unsigned int dataPos; // Position in the file where the actual data begins // unsigned int width, height; unsigned int imageSize; // = width*height*3 // Actual RGB data // unsigned char* data; // Open the file FILE* file = fopen(imagepath, "rb"); if (!file) { printf("Image could not be openedn"); return 0; } if (fread(header, 1, 54, file) != 54) { // If not 54 bytes read : problem printf("Not a correct BMP filen"); return false; } if (header[0] != 'B' || header[1] != 'M') { printf("Not a correct BMP filen"); return 0; } // Read ints from the byte array dataPos = *(int*)&(header[0x0A]); imageSize = *(int*)&(header[0x22]); width = *(int*)&(header[0x12]); height = *(int*)&(header[0x16]); // Some BMP files are misformatted, guess missing information if (imageSize == 0) imageSize = width * height * 3; // 3 : one byte for each Red, Green and Blue component if (dataPos == 0) dataPos = 54; // The BMP header is done that way // Create a buffer data = new unsigned char[imageSize]; // Read the actual data from the file into the buffer fread(data, 1, imageSize, file); //Everything is in memory now, the file can be closed fclose(file); }

片段着色器SimpleFragmentShader.fragmentshader中代码：

#version 330 core in vec2 UV; out vec3 color; uniform sampler2D myTextureSampler; void main(){ // Output color = color of the texture at the specified UV color = texture( myTextureSampler, UV ).rgb; }

顶点着色器SimpleVertexShader.vertexshader中代码：

#version 330 core layout(location = 0) in vec3 vertexPosition_modelspace; layout(location = 1) in vec2 vertexUV; // Output data ; will be interpolated for each fragment. out vec2 UV; // Values that stay constant for the whole mesh. uniform mat4 MVP; void main(){ // Output position of the vertex, in clip space : MVP * position gl_Position = MVP * vec4(vertexPosition_modelspace,1); // UV of the vertex. No special space for this one. UV = vertexUV; }

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