1. Texture map
wall.jpg (512×512) (learnopengl-cn.github.io)
Texture filtering is divided into: proximity and linear, which is the same as opencv image processing.
Multi-level gradient texture
Four sampling methods:
Code:
std_image.h
https://github.com/nothings/stb/blob/master/stb_image.h
picture
https://learnopengl-cn.github.io/img/01/06/container.jpg
main.cpp
If the load image reports an error, remember to add the macro: STB_IMAGE_IMPLEMENTATION
#include <glad/glad.h> #include <GLFW/glfw3.h> #include <iostream> #include "stb_image.h" #include <cmath> #include "shader.h" void framebuffer_size_callback(GLFWwindow* window, int width, int height); void processInput(GLFWwindow* window); // settings const unsigned int SCR_WIDTH = 800; const unsigned int SCR_HEIGHT = 600; int main() { //1.Initialization configuration glfwInit(); glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3); glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); #ifdef __APPLE__ glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE); #endif // __APPLE__ //2.gltf window creation GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LeranOpenGL", NULL, NULL); if (window == NULL) { std::cout << "Failed to create GLFW window" << std::endl; glfwTerminate(); return -1; } glfwMakeContextCurrent(window); glfwSetFramebufferSizeCallback(window, framebuffer_size_callback); //3. Load all GL function pointers if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) { std::cout << "Failed to initialize GLAD" << std::endl; return -1; } Shader ourShader("./texture.vs", "./texture.fs"); //4. Set vertex data float vertices[] = { // positions // colors // texture coords 0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, // top right 0.5f, -0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, // bottom right -0.5f, -0.5f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, // bottom left -0.5f, 0.5f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f // top left }; unsigned int indices[] = { 0, 1, 3, // first triangle 1, 2, 3 // second triangle }; unsigned int VBO, VAO, EBO; glGenVertexArrays(1, & amp;VAO); glGenBuffers(1, & amp;VBO); glGenBuffers(1, & amp;EBO);//Element Buffer Object: Element Buffer Object, EBO glBindVertexArray(VAO); \t //Copy the vertex array to the buffer for use by opengl glBindBuffer(GL_ARRAY_BUFFER, VBO); glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW); //Set the vertex attribute pointer glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0); glEnableVertexAttribArray(0); //Set the color attribute pointer glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float))); glEnableVertexAttribArray(1); //Set texture attribute pointer glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float))); glEnableVertexAttribArray(2); //Load and create texture unsigned int texture; glGenTextures(1, & amp;texture); glBindTexture(GL_TEXTURE_2D, texture); //Set texture wrapping parameters glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); //Set texture filtering parameters glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); //Load images and generate mipmaps int width, height, nrChannels; std::string filePath = R"(D:\CPlusProject\LearnOpenGL\DataSet\container.jpg)"; unsigned char* data = stbi_load(filePath.c_str(), & amp;width, & amp;height, & amp;nrChannels, 0); if (data) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data); glGenerateMipmap(GL_TEXTURE_2D); } else { std::cout << "Failed to load texture" << std::endl; } stbi_image_free(data); //5. Loop rendering while (!glfwWindowShouldClose(window)) { processInput(window); // render glClearColor(0.2f, 0.3f, 0.3f, 1.0f); glClear(GL_COLOR_BUFFER_BIT); //Bind texture glBindTexture(GL_TEXTURE_2D, texture); ourShader.use(); glBindVertexArray(VAO); glDrawElements(GL_TRIANGLES,6,GL_UNSIGNED_INT,0); glfwSwapBuffers(window); glfwPollEvents(); } glDeleteVertexArrays(1, & amp;VAO); glDeleteBuffers(1, & amp;VBO); glDeleteBuffers(1, & amp;EBO); glfwTerminate(); return 0; } // process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly //------------------------------------------------ -------------------------------------------------- ------- void processInput(GLFWwindow* window) { if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS) glfwSetWindowShouldClose(window, true); } // glfw: whenever the window size changed (by OS or user resize) this callback function executes //------------------------------------------------ ---------------------------------------- void framebuffer_size_callback(GLFWwindow* window, int width, int height) { // make sure the viewport matches the new window dimensions; note that width and // height will be significantly larger than specified on retina displays. glViewport(0, 0, width, height); }
2. Mixed textures
second picture
awesomeface.png (512×512) (learnopengl-cn.github.io)
texture.vs
#version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec3 aColor; layout (location = 2) in vec2 aTexCorrd; out vec3 ourColor; out vec2 TexCoord; void main() { gl_Position = vec4(aPos, 1.0); ourColor = aColor; TexCoord=vec2(aTexCorrd.x,aTexCorrd.y); }
texture.fs
#version 330 core out vec4 FragColor; in vec3 ourColor; in vec2 TexCoord; //texture sampler uniform sampler2D textureone; uniform sampler2D texturetwo; void main() { FragColor = mix(texture(textureone,TexCoord),texture(texturetwo,TexCoord),0.5); }
main.cpp
#include <glad/glad.h> #include <GLFW/glfw3.h> #include <iostream> #include "stb_image.h" #include <cmath> #include "shader.h" void framebuffer_size_callback(GLFWwindow* window, int width, int height); void processInput(GLFWwindow* window); // settings const unsigned int SCR_WIDTH = 800; const unsigned int SCR_HEIGHT = 600; int main() { //1.Initialization configuration glfwInit(); glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3); glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); #ifdef __APPLE__ glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE); #endif // __APPLE__ //2.gltf window creation GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LeranOpenGL", NULL, NULL); if (window == NULL) { std::cout << "Failed to create GLFW window" << std::endl; glfwTerminate(); return -1; } glfwMakeContextCurrent(window); glfwSetFramebufferSizeCallback(window, framebuffer_size_callback); //3. Load all GL function pointers if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) { std::cout << "Failed to initialize GLAD" << std::endl; return -1; } Shader ourShader("./texture.vs", "./texture.fs"); //4. Set vertex data float vertices[] = { // positions // colors // texture coords 0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, // top right 0.5f, -0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, // bottom right -0.5f, -0.5f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, // bottom left -0.5f, 0.5f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f // top left }; unsigned int indices[] = { 0, 1, 3, // first triangle 1, 2, 3 // second triangle }; unsigned int VBO, VAO, EBO; glGenVertexArrays(1, & amp;VAO); glGenBuffers(1, & amp;VBO); glGenBuffers(1, & amp;EBO);//Element Buffer Object: Element Buffer Object, EBO glBindVertexArray(VAO); \t //Copy the vertex array to the buffer for use by opengl glBindBuffer(GL_ARRAY_BUFFER, VBO); glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW); //Set the vertex attribute pointer glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0); glEnableVertexAttribArray(0); //Set the color attribute pointer glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float))); glEnableVertexAttribArray(1); //Set texture attribute pointer glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float))); glEnableVertexAttribArray(2); //Load and create texture unsigned int textureone,texturetwo; glGenTextures(1, & amp;textureone); glBindTexture(GL_TEXTURE_2D, textureone); //Set texture wrapping parameters glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); //Set texture filtering parameters glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); //Load images and generate mipmaps int width, height, nrChannels; stbi_set_flip_vertically_on_load(true); std::string filePath = R"(D:\CPlusProject\LearnOpenGL\DataSet\container.jpg)"; unsigned char* data = stbi_load(filePath.c_str(), & amp;width, & amp;height, & amp;nrChannels, 0); if (data) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data); glGenerateMipmap(GL_TEXTURE_2D); } else { std::cout << "Failed to load texture" << std::endl; } stbi_image_free(data); glGenTextures(1, & amp;texturetwo); glBindTexture(GL_TEXTURE_2D, texturetwo); //Set texture wrapping parameters glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); //Set texture filtering parameters glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); //Load images and generate mipmaps filePath = R"(D:\CPlusProject\LearnOpenGL\DataSet\awesomeface.png)"; unsigned char* data2 = stbi_load(filePath.c_str(), & amp;width, & amp;height, & amp;nrChannels, 0); if (data2) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data2); glGenerateMipmap(GL_TEXTURE_2D); } else { std::cout << "Failed to load texture" << std::endl; } stbi_image_free(data2); \t ourShader.use(); glUniform1i(glGetUniformLocation(ourShader.ID, "textureone"), 0);//Choose one of the two ourShader.setInt("texturetwo", 1);//Choose one of the two //5. Loop rendering while (!glfwWindowShouldClose(window)) { processInput(window); // render glClearColor(0.2f, 0.3f, 0.3f, 1.0f); glClear(GL_COLOR_BUFFER_BIT); //Bind texture glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, textureone); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texturetwo); ourShader.use(); glBindVertexArray(VAO); glDrawElements(GL_TRIANGLES,6,GL_UNSIGNED_INT,0); glfwSwapBuffers(window); glfwPollEvents(); } glDeleteVertexArrays(1, & amp;VAO); glDeleteBuffers(1, & amp;VBO); glDeleteBuffers(1, & amp;EBO); glfwTerminate(); return 0; } // process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly //------------------------------------------------ -------------------------------------------------- ------- void processInput(GLFWwindow* window) { if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS) glfwSetWindowShouldClose(window, true); } // glfw: whenever the window size changed (by OS or user resize) this callback function executes //------------------------------------------------ ---------------------------------------- void framebuffer_size_callback(GLFWwindow* window, int width, int height) { // make sure the viewport matches the new window dimensions; note that width and // height will be significantly larger than specified on retina displays. glViewport(0, 0, width, height); }