使用顶点缓冲区对象（VBO）渲染Kinect点云 [英] Rendering Kinect Point Cloud with Vertex Buffer Object (VBO)

问题描述

我想创建一个动态点云可视化工具。使用Kinect传感器每点更新点。抓住框架我使用OpenCV和GLUT来显示。
OpenCV API为点xyz位置返回640 x 480（float *），为rgb颜色数据返回640 x 480（int *）。
为了获得最大的性能，我试图在流模式中使用顶点缓冲区对象，而不是一个简单的顶点数组。我可以渲染它的顶点数组，但没有什么是用我的VBO实现呈现。我试着在声明中的一堆不同的顺序，但我找不到我失踪。有人可以试着指向正确的方向吗？这是简化的代码：（我已经重写了错误的版本，如Christian Rau所说，所以你们可以理解我的错误）

I´m trying to make a dynamic point cloud visualizer. The points are updated every frame with Kinect Sensor. To grab the frames I´m using OpenCV and GLUT to display. The OpenCV API returns a 640 x 480 (float *), for the points xyz position , and a 640 x 480 (int *) for the rgb color data. To get the maximum performance, I´m trying to use Vertex Buffer Object in stream mode instead of a simple Vertex Array. I´m being able to render it with Vertex Array, but nothing is being rendered with my VBO implementation. I tryied a bunch of different orders in the declarations, but i can't find what I'm missing. Can someone try to point me to the right direction? Here is the simpflified code: (I´ve rewrited the wrong version as asked by Christian Rau, so you guys can understand my mistakes)

int main()
{
    //Delaring variables, inittiating glut, setting camera and checking the compatibility as http://www.songho.ca/opengl/gl_vbo.html
    glutDisplayFunc(displayCB);
    glutIdleFunc(displayCB); 
    ... 
    //Inittiating the vertex buffers
    if(vboSupported)
    {
        glGenBuffers(1, &vertex_buffer);
        glBindBuffer(GL_ARRAY_BUFFER_ARB, buffer);
        glBufferData(GL_ARRAY_BUFFER_ARB, (sizeof(GLfloat) * 640 * 480 * 3), 0, GL_STREAM_DRAW_ARB);
        glBufferSubData(GL_ARRAY_BUFFER_ARB, 0,  (sizeof(float) * 640 * 480 * 3), point_cloud.points_position); 

        glGenBuffers(2, &color_buffer);
        glBindBuffer(GL_ARRAY_BUFFER_ARB, buffer);
        glBufferData(GL_ARRAY_BUFFER_ARB, (sizeof(GLbyte) * 640 * 480 * 3), 0, GL_STREAM_DRAW_ARB);
        glBufferSubData(GL_ARRAY_BUFFER_ARB, 0,  (sizeof(char) * 640 * 480 * 3), point_cloud.points_color); 
    }
    //glutMainLoop(), cleaning memory, ending main
    ..
}

//Updating the screen
void displayCB()
{
    point_cloud.update();

    // clear buffer
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

    // save the initial ModelView matrix before modifying ModelView matrix
    glPushMatrix();

        glBindBuffer(GL_ARRAY_BUFFER_ARB, color_buffer);
        glBufferSubData(GL_ARRAY_BUFFER_ARB, 0,  (sizeof(char) * 640 * 480 * 3), point_cloud.points_color); 
        glColorPointer(3, GL_UNSIGNED_BYTE, 0, 0);

        glBindBuffer(GL_ARRAY_BUFFER_ARB, vertex_buffer);
        glBufferSubData(GL_ARRAY_BUFFER_ARB, 0,  (sizeof(float) * 640 * 480 * 3), point_cloud.points_position); 
        glVertexPointer(3, GL_FLOAT, 0, 0));

        // enable vertex arrays
        glEnableClientState(GL_VERTEX_ARRAY);
        glEnableClientState(GL_COLOR_ARRAY);

        glDrawArrays(GL_POINT, 0, 640*480);

        glDisableClientState(GL_VERTEX_ARRAY);  // disable vertex arrays
        glDisableClientState(GL_COLOR_ARRAY);

        glBindBuffer(GL_ARRAY_BUFFER_ARB, 0);

    glPopMatrix();

    glutSwapBuffers();
}

推荐答案

PS：和运行，但是与Vertex Array版本相比，我看不到任何改进的平均性能。是不是好吗？
问题解决了。我做了三个改动：

PS: The program is up and running, but I can't see any improvement in the average performance when compared to the Vertex Array version. Is that alright? THE PROBLEM WAS SOLVED. I´ve done three alterations:

1 - I though that glGenBuffers first parameter was the number that
would be associated to the buffer, instead, its the number of
buffers that would be allocated. This doesn't matter anyway, because
now I'm using a single buffer and adding all the data to it. Didn't
solved the problem, but was going in the right way.

2 - There are two ways of being able to use OpenGL VBO functions.
First, you can bind the ARB  version functions by yourself OR you
can add glew.h and use glewInit() after starting an OpenGL context.
The second option is a LOT cleaner and I changed my code so I don't
use the ARB versions anymore. Still didn't solved the problem.

3 - Christian Rau asked me for glErrors in the code, so, I wrote it
after each OpenGL operation in displayCB. After glDrawArrays I got
an 0x00500 error, that means there is an invalid enum, so I noticed
I was using GL_POINT as parameter to glDrawArrays, instead of
GL_POINTS, so silly that makes me want to kill myself.

最终代码：

//EDIT: Added glew.h as a header and I´m not using the ARB version anymore
#include <glew.h>

    int main()
    {
        //Declaring variables, initiating glut, setting camera and checking the compatibility as http://www.songho.ca/opengl/gl_vbo.html
        glutDisplayFunc(displayCB);
        glutIdleFunc(displayCB); 
        ...

        //EDIT: IS VERY IMPORTANT TO ADD IT AS SOON AS YOU START AN OPENGL CONTEXT.
        initGlew();

        //Inittiating the vertex buffers
        if(vboSupported)
        {
           //EDIT: I was using two buffers, one for color and another for the vertex. I changed the code so I use  a single buffer now.
           //EDIT: Notice that I'm not using the ARB version of the functions anymore.
            glGenBuffers(1, &buffer);
            glBindBuffer(GL_ARRAY_BUFFER_ARB, buffer);
            glBufferData(GL_ARRAY_BUFFER_ARB, (sizeof(GLfloat) * 640 * 480 * 3) + (sizeof(GLbyte) * 640 * 480 * 3), 0, GL_STREAM_DRAW_ARB);
        }
        //glutMainLoop(), cleaning memory, ending main
        ..
    }

    //Updating the screen
    void displayCB()
    {
        point_cloud.update();

        // clear buffer
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

        // save the initial ModelView matrix before modifying ModelView matrix
        glPushMatrix();

            glBindBuffer(GL_ARRAY_BUFFER_ARB, buffer);
            glBufferSubData(GL_ARRAY_BUFFER_ARB, 0,  (sizeof(char) * 640 * 480 * 3), point_cloud.points_color); 
            glBufferSubData(GL_ARRAY_BUFFER_ARB, (sizeof(char) * 640 * 480 * 3), (sizeof(float) * 640 * 480 * 3), point_cloud.points_position);

            // enable vertex arrays
            glEnableClientState(GL_VERTEX_ARRAY);
            glEnableClientState(GL_COLOR_ARRAY);

            glColorPointer(3, GL_UNSIGNED_BYTE, 0, 0);
            //EDIT: Added the right offset at the vertex pointer position
            glVertexPointer(3, GL_FLOAT, 0, (void*)(sizeof(char) * 640 * 480 * 3));

            //EDIT: Was using GL_POINT instead of GL_POINTS
            glDrawArrays(GL_POINTS, 0, 640*480);

            glDisableClientState(GL_VERTEX_ARRAY);  // disable vertex arrays
            glDisableClientState(GL_COLOR_ARRAY);

            glBindBuffer(GL_ARRAY_BUFFER_ARB, 0);

        glPopMatrix();

        glutSwapBuffers();
    }

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