OpenGL基础（11）双重纹理 源码&显示效果

说明：本系列视频使用 mac平台的Xcode来实现，windows平台和Linux平台与之类似。

1 程序功能简介

主要是通过实战 理解双重纹理。上图中的纹理由下面两张纹理混合各50%构成，如下：

2 程序代码-双重纹理

2.1 核心源码

#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <learnopengl/filesystem.h>
#include <cmath>
#include <stb_image.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

//===================macro & header process start===================
//triangle draw test
#include <learnopengl/shader_s.h>
//===================macro & header process end===================
#define SHADER_ROOT_DIR "/Users/wangdaosheng/Desktop/X-Project/AGS_Repository/OpenGL/OpenGL-demo/openGLtest1/shader/"

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()
{
    // @1.1 glfw: initialize and configure---------------------
    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, GL_TRUE); // uncomment this statement to fix compilation on OS X
#endif
    
    // @1.2 glfw window creation---------------------
    GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "DaoshengOpenGL", NULL, NULL);
    if (window == NULL)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    // @1.3 glad: load all OpenGL function pointers---------------------
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }
    
    // @2 shader op
    Shader texture_box_Shader(SHADER_ROOT_DIR"texture.vs", SHADER_ROOT_DIR"texture.fs");
    
    float texture_box_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 texture_box_indices[] = {
        0, 1, 3, // first triangle
        1, 2, 3  // second triangle
    };
    unsigned int texture_box_VBO, texture_box_VAO, texture_box_EBO;
    
    glGenVertexArrays(1, &texture_box_VAO);
    glGenBuffers(1, &texture_box_VBO);
    glGenBuffers(1, &texture_box_EBO);
    glBindVertexArray(texture_box_VAO);
    glBindBuffer(GL_ARRAY_BUFFER, texture_box_VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(texture_box_vertices), texture_box_vertices, GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, texture_box_EBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(texture_box_indices), texture_box_indices, GL_STATIC_DRAW);
    
    // position attribute
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);
    // color attribute
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);
    // texture coord attribute
    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
    glEnableVertexAttribArray(2);
    
    unsigned int texture1,texture2;
    int width,height,nrChannels;
    //texture1 op start
    glGenTextures(1, &texture1);
    glBindTexture(GL_TEXTURE_2D, texture1); // all upcoming GL_TEXTURE_2D operations now have effect on this texture object
    // set the texture wrapping parameters
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);    // set texture wrapping to GL_REPEAT (default wrapping method)
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    // set texture filtering parameters
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    stbi_set_flip_vertically_on_load(true); // tell stb_image.h to flip loaded texture's on the y-axis.
    unsigned char *texture1_data = stbi_load(FileSystem::getPath("resources/textures/container.jpg").c_str(), &width, &height, &nrChannels, 0);
    if (texture1_data)
    {
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, texture1_data);
        glGenerateMipmap(GL_TEXTURE_2D);
    }
    else
    {
        std::cout << "Failed to load texture1" << std::endl;
    }
    stbi_image_free(texture1_data);
    //texture1 op end
    
    //texture2 op start
    glGenTextures(1, &texture2);
    glBindTexture(GL_TEXTURE_2D, texture2); // all upcoming GL_TEXTURE_2D operations now have effect on this texture object
    // set the texture wrapping parameters
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);    // set texture wrapping to GL_REPEAT (default wrapping method)
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    // set texture filtering parameters
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    stbi_set_flip_vertically_on_load(true); // tell stb_image.h to flip loaded texture's on the y-axis.
    unsigned char *texture2_data = stbi_load(FileSystem::getPath("resources/textures/brickwall_normal.jpg").c_str(), &width, &height, &nrChannels, 0);
    if (texture2_data)
    {
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, texture2_data);
        glGenerateMipmap(GL_TEXTURE_2D);
    }
    else
    {
        std::cout << "Failed to load texture2" << std::endl;
    }
    stbi_image_free(texture2_data);
    //texture2 op end
    
    // render loop
    while (!glfwWindowShouldClose(window))
    {
        // input process
        processInput(window);
        // render process
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        texture_box_Shader.use();

        // render container
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, texture1);
        glUniform1i(glGetUniformLocation(texture_box_Shader.getID(), "texture1"), 0);
        glActiveTexture(GL_TEXTURE1);
        glBindTexture(GL_TEXTURE_2D, texture2);
        glUniform1i(glGetUniformLocation(texture_box_Shader.getID(), "texture2"), 1);

        glBindVertexArray(texture_box_VAO);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
        glBindVertexArray(0);
        
        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    // optional: de-allocate all resources once they've outlived their purpose:
    glDeleteVertexArrays(1, &texture_box_VAO);
    glDeleteBuffers(1, &texture_box_VBO);
    glDeleteBuffers(1, &texture_box_EBO);
    glfwTerminate(); // glfw: terminate, clearing all previously allocated GLFW resources.
    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);
}

2.2 关键头文件

参考上一章节OpenGL基础（10）纹理四边形 源码&显示效果即可。

2.3 纹理代码

@1 texture.vs 顶点着色器代码

#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aColor;
layout (location = 2) in vec2 aTexCoord;

out vec3 ourColor;
out vec2 TexCoord;

void main()
{
	gl_Position = vec4(aPos, 1.0);
	ourColor = aColor;
	TexCoord = vec2(aTexCoord.x, aTexCoord.y);
}

@1 texture.fs 片段着色器代码

#version 330 core
out vec4 FragColor;

in vec3 ourColor;
in vec2 TexCoord;

// texture sampler
uniform sampler2D texture1;
uniform sampler2D texture2;

void main()
{
    FragColor = mix(texture(texture1, TexCoord), texture(texture2, TexCoord), 0.5);
}

该系列文章主要参考openGL官网 和学习 learnopenGL官网 进行知识体系的梳理和重构，重在形成自己对openGL知识的理解和知识体系。