c++ - 索引绘图 : data copied from a working example is displayed incorrectly

Question

我有这段代码:

#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <iostream>

void keyCallback(GLFWwindow* window, int key, int scancode, int action, int mods) {
    if(key == GLFW_KEY_ESCAPE && action == GLFW_PRESS) {
        glfwSetWindowShouldClose(window, GLFW_TRUE);
    }
}

int main() {
    glfwInit();

    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 5);

    auto window = glfwCreateWindow(800, 600, "title", NULL, NULL);
    glfwMakeContextCurrent(window);
    glfwSetKeyCallback(window, keyCallback);

    glewExperimental = true;
    glewInit();

    glViewport(0, 0, 800, 600);

    static const char* vsSource[] = {
        "#version 450 core\n"
        "layout (location = 0) in vec3 position;"
        "uniform mat4 mvp;"
        "out vec3 pos;"
        "void main() {"
        "gl_Position = mvp * vec4(position, 1.0);"
        "pos = position;"
        "}"
    };

    static const char* fsSource[] = {
        "#version 450 core\n"
        "in vec3 pos;"
        "out vec4 color;"
        "void main() {"
        "color = vec4(pos, 1.0) * 0.5 + 0.5;"
        "}"
    };

    static const GLfloat clearColor[] = { 0.1f, 0.1f, 0.1f, 1.0f };

    static const GLfloat vertices[] = {
            -0.25f, -0.25f, -0.25f,
            -0.25f,  0.25f, -0.25f,
             0.25f, -0.25f, -0.25f,
             0.25f,  0.25f, -0.25f,
             0.25f, -0.25f,  0.25f,
             0.25f,  0.25f,  0.25f,
            -0.25f, -0.25f,  0.25f,
            -0.25f,  0.25f,  0.25f,
    };

    static const GLushort indices[] = {
            0, 1, 2,
            2, 1, 3,
            2, 3, 4,
            4, 3, 5,
            4, 5, 6,
            6, 5, 7,
            6, 7, 0,
            0, 7, 1,
            6, 0, 2,
            2, 4, 6,
            7, 5, 3,
            7, 3, 1
    };

    auto vs = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vs, 1, vsSource, NULL);
    glCompileShader(vs);

    auto fs = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fs, 1, fsSource, NULL);
    glCompileShader(fs);

    auto program = glCreateProgram();
    glAttachShader(program, vs);
    glAttachShader(program, fs);
    glLinkProgram(program);
    glDeleteShader(vs);
    glDeleteShader(fs);

    int logLength = 1024;
    char* log = new char[logLength];
    glGetProgramInfoLog(program, logLength, &logLength, log);
    std::cout << log << std::endl;

    glUseProgram(program);

    auto mvpLocation = glGetUniformLocation(program, "mvp");

    glm::mat4 projection = glm::perspective(50.0f, 800.0f/600.0f, 0.1f, 1000.0f);
    glm::mat4 model = glm::translate(glm::mat4(1.0f), glm::vec3(0.0, 0.0, -10.0));
    glm::mat4 mvp;

    GLuint vao, vbo, ibo;

    glCreateVertexArrays(1, &vao);
    glBindVertexArray(vao);

    glCreateBuffers(1, &vbo);
    glNamedBufferStorage(vbo, sizeof(vertices), vertices, GL_MAP_READ_BIT);
    glVertexArrayVertexBuffer(vao, 0, vbo, 0, 2 * sizeof(GLfloat));
    glVertexArrayAttribFormat(vao, 0, 3, GL_FLOAT, GL_FALSE, NULL);
    glVertexArrayAttribBinding(vao, 0, 0);
    glEnableVertexArrayAttrib(vao, 0);

    glCreateBuffers(1, &ibo);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo);
    glNamedBufferStorage(ibo, sizeof(indices), indices, GL_MAP_READ_BIT);

    float timer = 0.0f;

    static const GLfloat depthClear = 1.0f;

    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LESS);

    glEnable(GL_CULL_FACE);

    glfwSwapInterval(1);

    while(!glfwWindowShouldClose(window)) {
        glClearBufferfv(GL_COLOR, 0, clearColor);
        glClearBufferfv(GL_DEPTH, 0, &depthClear);
        mvp = projection * model * glm::rotate(glm::mat4(), timer / 1000.0f, glm::vec3(0.0f, 1.0f, 1.0f));
        glUniformMatrix4fv(mvpLocation, 1, GL_FALSE, glm::value_ptr(mvp));
        glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_SHORT, 0);
        glfwPollEvents();
        glfwSwapBuffers(window);
        timer += 1.0f;
    }

    glfwTerminate();
    return 0;
}

我编译它:

clang++ -std=c++11 main.cpp -o cube -lGLEW -lglfw3 -lGL -gsplit-dwarf

这就是我编译和运行它时的显示方式(期待一个旋转的立方体):

我的问题是:这里发生了什么？ 索引和顶点都是从相似的、有效的示例代码片段中复制的——也就是说，它们是相同的。

我花了最后一个小时寻找任何显着差异和问题的原因，但找不到。示例代码(来自 OpenGL SB7)编译、运行并显示一个立方体。它使用较旧的 OpenGL api(例如 glBufferData，我使用 glNamedBufferStorage)。

我尝试了不同的顶点和索引集(来自网络上的不同示例)，所有的顶点和索引都是这样显示的。所以我认为这不是数据的错，而是我的代码中有某些东西导致了这个。不幸的是，我找不到内容和位置。

Answer 1

glVertexArrayVertexBuffer(vao, 0, vbo, 0, 2 * sizeof(GLfloat));
                                          ^ wat

vertcies 的 Stride 是错误的。应该是3:

glVertexArrayVertexBuffer(vao, 0, vbo, 0, 3 * sizeof(GLfloat));

我猜几何移植前的代码使用的是二维几何体。