c++ - Representación de Kinect Point Cloud con Vertex Buffer Object(VBO)

opengl stream

Question

Estoy tratando de hacer un visualizador dinámico de nubes de puntos. Los puntos se actualizan en cada cuadro con Kinect Sensor. Para agarrar los marcos, estoy usando OpenCV y GLUT para visualizar. La API de OpenCV devuelve 640 x 480 (float *), para la posición de los puntos xyz, y 640 x 480 (int *) para los datos de color rgb. Para obtener el máximo rendimiento, estoy tratando de usar Vertex Buffer Object en modo de secuencia en lugar de una simple Vertex Array. Puedo renderizarlo con Vertex Array, pero no se está procesando nada con mi implementación de VBO. Intenté un montón de órdenes diferentes en las declaraciones, pero no puedo encontrar lo que me falta. ¿Alguien puede tratar de señalarme en la dirección correcta? Aquí está el código simplificado: (he reescrito la versión incorrecta como Christian Rau me preguntó, para que puedan entender mis errores)

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();
}

Answer 1

PD: El programa está en funcionamiento, pero no puedo ver ninguna mejora en el rendimiento promedio en comparación con la versión de Vertex Array. ¿Está eso bien? EL PROBLEMA FUE RESUELTO. He hecho tres alteraciones:

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.

El código final:

//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();
    }