c++ - 变换反馈的完整设置(openGL)

Question

GLSL 1.50，openGL 3.3。

我最近一直在尝试让我的转换反馈发挥作用，但没有成功。在 glBeginTranformFeedback() 之后我仍然收到错误，并且由于我没有找到任何完整的工作代码，我已经用我发现的一些代码和文档积累了我的知识，它现在应该运行良好但我遗漏了一些东西。因此，如果有人有完整的代码(缓冲区的初始化、设置、更新、渲染、回读)，那肯定会有所帮助，如果你不知道，但知道发生了什么，你可以看看我的代码。我排除了一些基准测试、Windows 处理及其创建:

int main()
{
    bool fullsize = false, paused = false; 
    std::string caption = "Tester";

    GLuint dataVAO,speedUpdateVBO,dataVBO;
    std::vector<vector3f> dataW;

    // Create the main rendering window

    init(); //just some camera commands

    UniShader shader; //my shader class keeps everything together
    shader.init();
    shader.addShader("test.vert");
    shader.addShader("test.frag");
    shader.newAttributeVariable("speed");
    shader.newFeedbackVarying("sp");
    shader.linkShader();
    shader.use();

    //init some data
    dataW.push_back(vector3f(0,1,0));

    //creating VAO
    glGenVertexArrays(1,&dataVAO);
    glBindVertexArray(dataVAO);
    //creating VBO
    glGenBuffers(1,&dataVBO);
    glBindBuffer(GL_ARRAY_BUFFER,dataVBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vector3f), 0, GL_DYNAMIC_DRAW);
    glVertexAttribPointer(shader.getAttributeIndex("speed"), 3, GL_FLOAT, GL_FALSE, 0, 0);

    glGenBuffers(1, &speedUpdateVBO);
    glBindBuffer(GL_TRANSFORM_FEEDBACK_BUFFER, speedUpdateVBO);
    glBufferData(GL_TRANSFORM_FEEDBACK_BUFFER, sizeof(vector3f), NULL, GL_DYNAMIC_COPY);
    glBindBufferBase(GL_TRANSFORM_FEEDBACK_BUFFER, 0, speedUpdateVBO); 
    glBindVertexArray(0);


    while (App.IsOpened())
    {
            App.SetActive();
        benchP = Clock.GetElapsedTime();

        //update calls
        if(!paused)
            //update
        benchU = Clock.GetElapsedTime();

        //render calls
        glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glColor3f(0.6f,0.7f,0.7f);

    GLuint query;
    GLuint count = 0;

    glGenQueries(1, &query);

    glEnableVertexAttribArray(shader.getAttributeIndex("speed"));

    glBindVertexArray(dataVAO);

    glBindBuffer(GL_ARRAY_BUFFER,dataVBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vector3f)*dataW.size(), &dataW[0], GL_DYNAMIC_DRAW);
    glBindBuffer(GL_TRANSFORM_FEEDBACK_BUFFER, speedUpdateVBO);
    glBufferData(GL_TRANSFORM_FEEDBACK_BUFFER, sizeof(vector3f)*dataW.size(), NULL, GL_DYNAMIC_COPY);

    glBindBufferBase(GL_TRANSFORM_FEEDBACK_BUFFER, 0, speedUpdateVBO); 
    glEnable(GL_RASTERIZER_DISCARD);
    glBeginQuery(GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN, query);
    printOglError(); //Until this everything OK, I think
    glBeginTransformFeedback(GL_POINTS); 
    printOglError(); //This one prints out Invalid Value

    glDrawArrays(GL_POINTS,0,dataW.size());

    glEndTransformFeedback();
    glEndQuery(GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN); 
    glDisable(GL_RASTERIZER_DISCARD);

    //retrieve updated data
    glGetQueryObjectuiv(query, GL_QUERY_RESULT, &count); //count is 0 -> nothing happend

    glBindVertexArray(0);
    glDisableVertexAttribArray(shader.getAttributeIndex("speed"));

    glDeleteQueries(1, &query);

    App.Display();
    //some other benchmark stuff
}

着色器: 垂直

#version 150 core
in vec3 speed;

varying vec3 sp;

const float gravity_constant = 9.81f;

void main(){
    sp = speed;
    sp += vec3(0,-gravity_constant,0);
}

片段

#version 150 core
varying vec3 sp;

void main (void)
{
    vec3 c = sp;
    gl_FragColor = vec4(c,1.0);
}

片段着色器仅用于 GLSL 优化。如果不使用 sp，GLSL 会清除它。 可能存在一些小错误，因为我从具有多个失败的更大代码中提取了它。

Answer 1

看看OpenGL Samples Pack .您可能对 ogl-330-transform-feedback.cpp 和 ogl-400-transform-feedback-object.cpp 感兴趣。你甚至可以检查 January 2011 OpenGL drivers status最新的驱动程序是否与提供的示例有任何问题。

祝你好运。