OpenGL 扭曲纹理

Question

我正在尝试显示纹理，但由于某种原因它没有正确显示，它被扭曲了。

这是我的源代码：

#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

void processInput(GLFWwindow *window)
{
    if(glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);
}

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    glViewport(0, 0, width, height);
}

int main(void)
{
    int success;
    char infoLog[512];

    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
    if (window == NULL)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);

     if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
     {
         std::cout << "Failed to initialize GLAD" << std::endl;
         return -1;
     }

    glViewport(0, 0, 800, 600);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    const char *vertexShaderSource = "#version 330 core\n"
                                     "layout (location = 0) in vec3 aPos;\n"
                                     "layout (location = 1) in vec2 aTexCoord;\n"
                                     "out vec2 TexCoord;\n"
                                     "void main()\n"
                                     "{\n"
                                     " gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
                                     "TexCoord = aTexCoord;"
                                     "}[=10=]";
    unsigned int vertexShader;
    vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    glCompileShader(vertexShader);
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
    if(!success)
    {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
    }

    const char* fragmentShaderSource = "#version 330 core\n"
                                       "out vec4 FragColor;\n"
                                       "in vec2 TexCoord;\n"
                                       "uniform sampler2D ourTexture;\n"
                                       "void main()\n"
                                       "{\n"
                                       "FragColor = texture(ourTexture, TexCoord);\n"
                                       "}[=10=]";
    unsigned int fragmentShader;
    fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
    glCompileShader(fragmentShader);
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
    if(!success)
    {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
    }

    unsigned int shaderProgram;
    shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);
    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
    if(!success) {
        glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
    }

    float vertices[] = {
                //positions                                 //texture coords
              1.0f,   1.0f,  0.0f,          1.0f,  1.0f,// top right
              1.0f,  -1.0f,  0.0f,          1.0f,  0.0f,// bottom right
            -1.0f, -1.0f, 0.0f,          0.0f, 0.0f,// bottom left
            -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;
    unsigned int EBO;
    unsigned int VAO;

    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &EBO);
    glGenBuffers(1, &VBO);

    glBindVertexArray(VAO);

    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);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);

    unsigned int texture;
    glGenTextures(1, &texture);
    //glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, texture);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_TEXTURE_WRAP_S);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_TEXTURE_WRAP_T);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    int width, height, nrChannels;
    stbi_set_flip_vertically_on_load(1);
    unsigned char *data = stbi_load("../asd.jpg", &width, &height,&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
    {
        if(stbi_failure_reason())
            std::cout << stbi_failure_reason();
    }

    while(!glfwWindowShouldClose(window))
    {
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        glBindTexture(GL_TEXTURE_2D, texture);
        glUseProgram(shaderProgram);
        glBindVertexArray(VAO);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
        processInput(window);

        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);
    glfwTerminate();

    return 0;
}

结果：

预期结果：

我检查了所有坐标和位置，一切看起来都是正确的。我不知道为什么纹理显示不正确。顶点和片段着色器似乎也是正确的。

Answer 1

默认情况下，OpenGL 假定图像的每一行的开始对齐到 4 个字节。这是因为默认情况下 GL_UNPACK_ALIGNMENT 参数为 4。由于图像具有 3 个颜色通道 (GL_RGB)，并且被紧密打包，因此图像的一行大小可能不会对齐到 4 个字节。
当具有 3 个颜色通道的 RGB 图像被加载到纹理对象并且 3*width 不能被 4 整除时，GL_UNPACK_ALIGNMENT 必须设置为 1，然后用 glTexImage2D 指定纹理图像：

glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);

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