OpenGL_Learn05 (texture)

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);
}