glGenVertexArrays 在主循环中不创建唯一的 VAO，但在其他情况下工作

Question

我目前正在为我一直在编写的游戏引擎开发一个小型编辑器。我已经使用 Qt 5.6 设置了一个文件菜单，其中有一个选项可以添加一个模型，该模型可以创建一个新模型并将其添加到渲染引擎管理器中。在 Mac OSX 10.11（使用 OpenGL 3 或 4）上，这工作正常。在 Ubuntu 16.04 上，它只能稍微起作用。我可以在主循环之外初始化任意数量的模型。但是在主循环内，我只能初始化与在主循环外初始化的模型一样多的模型。当我在 IDE 中启动 gdb 时，问题似乎与 VAO 相关。在 OSX 上，无论我在哪里创建网格，都会为每个模型初始化一个新的 VAO。在 Ubuntu 上，在主循环之外为每个网格生成新的 VAO。在主循环内，绘制的网格与先前在主循环外创建的网格具有相同的 VAO。一旦我创建的模型多于在主循环外创建的模型并且生成了新的 VAO，模型就不会绘制。

总而言之，在 Ubuntu 中，主循环外的所有模型都有自己的 VAO。在主循环中，VAO GLuint 句柄再次从 2 开始重新计数。一旦 handle/tag 计数过去，但是许多模型在主循环之外被初始化，模型停止绘制。它工作得很好 Mac OSX。我怀疑这是一个 OpenGL/Qt 问题，所以尽管引擎有很多额外的代码，但我认为这个问题很公平。 Link: https://github.com/BennetLeff/engine

由于有很多文件，我将只包含我认为必要的文件，但我也会 link 到 github 项目。很抱歉出现大量代码转储，但请告诉我是否还有其他我可以提供的内容。

Mesh.cpp

#include "Mesh.h"
#include "Transform.h"

#include <stdio.h>

Mesh::Mesh(std::vector<glm::vec3> vertices, std::vector<glm::vec3> normals, std::vector<glm::vec2> textures, std::vector<GLuint> indices)
{
    drawCount_ = indices.size();

  glGenVertexArrays(1, &vertexArrayObject_);
    glBindVertexArray(vertexArrayObject_);

    glGenBuffers(NUMBUFFERS, vertexBufferObject_);

    // Position Attrib
    glBindBuffer(GL_ARRAY_BUFFER, vertexBufferObject_[POSITION_VB]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices[0]) * vertices.size(), vertices.data(), GL_STATIC_DRAW);
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 0, 0);

    // Texture Attrib
    glBindBuffer(GL_ARRAY_BUFFER, vertexBufferObject_[TEXCOORD_VB]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(textures[0]) * textures.size(), textures.data(), GL_STATIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, 0);

  // Normals Attrib
  glBindBuffer(GL_ARRAY_BUFFER, vertexBufferObject_[NORMAL_VB]);
  glBufferData(GL_ARRAY_BUFFER, sizeof(normals[0]) * normals.size(), normals.data(), GL_STATIC_DRAW);
  glEnableVertexAttribArray(2);
  glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, 0, 0);

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vertexBufferObject_[INDEX_VB]);
  glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices[0]) * indices.size(), indices.data(), GL_STATIC_DRAW);

    glBindVertexArray(0);

  fprintf(stderr, "vao val %d\n", vertexArrayObject_);
}

Mesh::~Mesh()
{
    glDeleteVertexArrays(1, &vertexArrayObject_);
}

void Mesh::draw()
{
  glBindVertexArray(vertexArrayObject_);
    glDrawElements(GL_TRIANGLES, drawCount_, GL_UNSIGNED_INT, 0);
    glBindVertexArray(0);
  if (glGetError())
      printf("GL error %d", glGetError());
}

Main.cpp

#include <stdio.h>

#ifdef __APPLE__
    #include <OpenGL/gl3.h>
#else
    #include <GL/glew.h>
#endif

#include "Camera.h"
#include "Model.h"

#include "Editor.h"
#include "RenderEngine.h"

#include <QApplication>

bool quit = false;

int main(int argc, char* argv[])
{
    auto WIDTH = 1024;
    auto HEIGHT = 800;

    /* 
     * Sets up a QApplication
     * with the proper formatting. This allows
     * GL versions to be set and so forth. Then
     * the QApplication is polled in the main loop
     * for events.
    */

    QApplication app(argc, argv);
    QSurfaceFormat format;
    format.setSamples(16);
    format.setDepthBufferSize(24);
    format.setStencilBufferSize(8);
    format.setVersion(4, 3);
    format.setProfile(QSurfaceFormat::CoreProfile);
    QSurfaceFormat::setDefaultFormat(format);

    // Sets up Rendering Engine and Editor.
    auto cam = new Camera(glm::vec3(0, 6, -20), 70.0f, (float) WIDTH / (float) HEIGHT, 0.01f, 1000.0f);
    RenderEngine* engine = new RenderEngine(cam);
    Editor editor(engine, WIDTH, HEIGHT);

    editor.showEditor();

    /*
     * Must call Editor.show() before any other
     * OpenGL calls. This is mostly because of Qt.
    */
    // auto house = Model("./res/farm house/OBJ/Farmhouse OBJ.obj", "./res/farm house/Textures/Farmhouse Texture.jpg");
    // house.transform->getPosition()->z = 40;

    // auto model = Model("./res/Alfred/Alfred.obj", "./res/Alfred/alfred_dif.png");
    // auto model2 = Model("./res/Alfred/Alfred.obj", "./res/Alfred/alfred_dif.png");

    float counter = 0.0f;

    while (editor.isVisible())
    {
        app.processEvents();
        // model.transform->getRotation()->y = float(editor.getSliderValue()) / 10;
        // model.transform->getPosition()->z = editor.getManValue();
        counter += 0.1f;

        /*
         * Just updating window for now because
         * it may be faster. Need to benchmark this
         * and determine what is necessary.
        */
        editor.getWindow()->update();
    }

    return 0;
}

GUIWindow.cpp（继承自QOpenGLWidget、QOpenGLFunctions）

#include <GL/glew.h>
#include "GUIWindow.h"

GUIWindow::GUIWindow(QWidget* parent, RenderEngine* engine) :
    QOpenGLWidget(parent), engine(engine) { }

void GUIWindow::initializeGL()
{
    // Set up the rendering context, load shaders and other resources, etc.:
    initializeOpenGLFunctions();

    // If not on OSX we need to include
    // OpenGL as an extension
    #ifndef __APPLE__
        glewExperimental = GL_TRUE;

        GLenum err = glewInit();
        if (GLEW_OK != err) {
            /* Problem: glewInit failed, something is seriously wrong. */
            fprintf(stderr, "Error: %s\n", glewGetErrorString(err));
        }
    #endif

    // Depth test not enabled by default.
    glEnable(GL_DEPTH_TEST);
}

void GUIWindow::resizeGL(int w, int h) {  }

void GUIWindow::paintGL()
{
    // Draw the scene
    clear(0.1, 0.4, 0.6, 1.0);

    // Draw all Models
    engine->draw();
}

void GUIWindow::clear(float r, float g, float b, float a)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
    glClearColor(r, g, b, a);
}

GUIWindow::~GUIWindow() { }

Model.cpp（不包括仅从 AssImp 获取数据的模型加载）

void Model::draw(Camera* cam)
{
    shader.draw();
    shader.update(transform, cam);
    tex.bind(0);
    modelMesh->draw();
}

void Model::bindTexture(Texture tex)
{
    this->tex = tex;
}

RenderingEngine.cpp

#include "RenderEngine.h"

RenderEngine::RenderEngine(Camera* cam)
    : cam(cam)
{
    this->init();
}

void RenderEngine::init()
{
    // If not on OSX we need to include
    // OpenGL as an extension
    #ifndef __APPLE__
        glewExperimental = GL_TRUE;

        GLenum err = glewInit();
        if (GLEW_OK != err) {
            /* Problem: glewInit failed, something is seriously wrong. */
            fprintf(stderr, "Error: %s\n", glewGetErrorString(err));
        }

        glEnable(GL_DEPTH_TEST);
    #endif
}

void RenderEngine::addModel(Model model)
{
    printf("added model \n");
    this->models.push_back(model);
    for (int i = 0; i < this->models.size(); i++)
        printf("Model Pos: (%g, %g, %g) \n", models[i].transform->getPosition()->x,
               models[i].transform->getPosition()->y,
               models[i].transform->getPosition()->z);
    printf("there are %d models now \n", this->models.size());
}

void RenderEngine::draw()
{
     for (int i = 0; i < this->models.size(); i++)
        models[i].draw(this->cam);
}

Editor.cpp（减去大多数刚刚设置 window 的 Qt 调用）

#include "Editor.h"

Editor::Editor(RenderEngine* renderEngine, int width, int height)
{
    frame = 0;
    this->width = width;
    this->height = height;
    this->engine = renderEngine;
    this->window = new GUIWindow(0, renderEngine);
}

void Editor::initialize()
{
    // Set up the rendering context, load shaders and other resources, etc.:
    // initializeOpenGLFunctions();
    glViewport(0, 0, width, height);
    setupWidgets();
}


float Editor::getRandNum()
{
    srand(time(0));
    float num = rand() % 10 + 1;
    fprintf(stderr, "%d \n", num);
    return num;
}

void Editor::addModelToScene()
{
    srand (time(NULL));

    auto trans = new Transform();
    trans->getPosition()->x = rand() % 10 + 1;
    trans->getPosition()->y = rand() % 10 + 1;
    trans->getPosition()->z = rand() % 10 + 1;
    engine->addModel(Model("./res/Alfred/Alfred.obj", "./res/Alfred/alfred_dif.png", trans));
    fprintf(stderr, "Add a Model \n");
}

void Editor::showEditor()
{
    // Sets up the rest of the widgets locations.
    setupWidgets();
    // Sets up the QMainWindow.
    this->show();
}

void Editor::addModel(Model model)
{
    engine->addModel(model);
}

Answer 1

我不知道为什么我被否决了，但我终于弄清楚了这个问题。在 Editor::addModelToScene() 中，我需要在调用 addModel() 之前调用 window.makeCurrent()。我完全不知道为什么这会在 OSX 上起作用。还要感谢让我有了尝试这个的想法。

glGenVertexArrays 在主循环中不创建唯一的 VAO，但在其他情况下工作

glGenVertexArrays Not creating unique VAO when in Main loop but works otherwise

c++

opengl

macos

qt

vertex-array-object