用FBO绘制到渲染缓冲区

我的问题非常接近这个:FBO和渲染到renderbuffer。我目前正在尝试在renderbuffer上渲染一个简单的三角形，就像本教程中一样。我的程序是Igor Pro的一个插件，它使用OpenGL执行屏幕外渲染。

不幸的是，当我试图读取像素值时，我只得到零。我已经知道initBuffers函数是有效的，问题出在display函数上。

2)我想渲染一个顶点数据列表，而不使用直接模式。我以前用vbo做过一个实现。我可以重用这些代码吗?

/*  
RenderTriangle.cpp
*/
#include "VC10triangulation.h"
#include "XOPStandardHeaders.h"         // Include ANSI headers, Mac headers, IgorXOP.h, XOP.h and XOPSupport.h
#include <vector>

// Prototypes
HOST_IMPORT int main(IORecHandle ioRecHandle);
// Global Variables
const int windowSize = 512;
int size,el_size;
float* waveX=NULL;
float* waveY=NULL;
float* waveZ=NULL;
GLuint framebuffer, renderbuffer;
// Custom error codes
#define OLD_IGOR 1 + FIRST_XOP_ERR
#define NON_EXISTENT_WAVE 2 + FIRST_XOP_ERR
#define REQUIRES_SP_OR_DP_WAVE 3 + FIRST_XOP_ERR
#pragma pack(2)     // All structures passed to Igor are two-byte aligned.
typedef struct WaveParams {
  waveHndl waveZ;
  waveHndl waveY;
  waveHndl waveX;   
  double result;
} WaveParams, *WaveParamsPtr;
#pragma pack()      // Restore default structure alignment
// Prototypes of the OpenGL callbacks
void initBuffers(void);
void display(void);
void readPixels(void);
void initBuffers(void){
  GLenum status;
  //Generate the fbo where we will bind a render buffer object
  glGenFramebuffers(1,&framebuffer);
  glBindFramebuffer(GL_DRAW_FRAMEBUFFER,framebuffer);
  //Generate render buffer object
  glGenRenderbuffers(1,&renderbuffer);
  glBindRenderbuffer(GL_RENDERBUFFER,renderbuffer);
  glRenderbufferStorage(GL_RENDERBUFFER,GL_RGBA8, windowSize, windowSize);
  glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, renderbuffer);
  status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
  if (status != GL_FRAMEBUFFER_COMPLETE)
    XOPNotice("Error Framebuffer Complete");
  else
    XOPNotice("Framebuffer Complete");
}
void display(void){//display a simple triangle
  glViewport(0,0,windowSize,windowSize);
  glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
  glClearColor(1.0f, 0.0f, 0.0f,0.5f);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glLoadIdentity();
  glBegin(GL_TRIANGLES);// Drawing Using Triangles
    glColor3f(1.0f, 0.0f, 0.0f);glVertex3f( 0.0f, 1.0f, 0.0f);// Top
    glColor3f(1.0f, 0.0f, 0.0f);glVertex3f(-1.0f,-1.0f, 0.0f);// Bottom Left
    glColor3f(1.0f, 0.0f, 0.0f);glVertex3f( 1.0f,-1.0f, 0.0f);// Bottom Right
  glEnd();// Finished Drawing The Triangle
  glFlush();
}
// Idle callback function for OpenGL API
void readPixels(void){
  //glBindFramebuffer(GL_FRAMEBUFFER, 0);
  float* pixels = (float*)malloc(windowSize*windowSize*sizeof(float));
  glReadBuffer(GL_COLOR_ATTACHMENT0);
  glReadPixels(0, 0, windowSize, windowSize, GL_DEPTH_COMPONENT, GL_FLOAT, pixels);
  waveHndl waveH;
  char waveName[MAX_OBJ_NAME+1];
  DataFolderHandle dfH;
  CountInt dimensionSizes[MAX_DIMENSIONS+1];
  float* wp;
  IndexInt p;
  double offset, delta;
  int err;
  strcpy(waveName, "wave1");
  dfH = NULL; // Put wave in the current data folder
  MemClear(dimensionSizes, sizeof(dimensionSizes));
  dimensionSizes[ROWS] = windowSize; // Make 1D wave with 100 points
  dimensionSizes[COLUMNS] = windowSize;
  if (MDMakeWave(&waveH, waveName, dfH, dimensionSizes, NT_FP32, 1))
    XOPNotice("Can't create wave when reading pixel values");
  wp = (float*)WaveData(waveH); // Get a pointer to the wave data
  for(p = 0; p < windowSize*windowSize; p++)
  *wp++ = pixels[p]; // Store point number in wave

}
void deleteBuffers(){
  glDeleteFramebuffers(1,&framebuffer);
  glDeleteRenderbuffers(1,&renderbuffer);
}
// Main function for the XOP
extern "C" int
  RenderTriangle(WaveParamsPtr p)
{
  //Pointers to the input waves
  waveX=(float*)WaveData(p->waveX);
  waveY=(float*)WaveData(p->waveY);
  waveZ=(float*)WaveData(p->waveZ);
  //Creates the window
  char *myargv [1];
  int myargc=1, windowHandle;
  myargv [0]=strdup ("RenderTriangle");
  glutInit(&myargc,myargv);
  glutInitDisplayMode(GLUT_SINGLE | GLUT_DEPTH | GLUT_RGB);
  glutInitWindowSize(windowSize,windowSize);
  windowHandle = glutCreateWindow("OpenGL");
  //Init glew library 
  glewInit(); 
  //Creates the fbo and render buffer object
  initBuffers(); 
  display();
  readPixels();
  //Deletes the fbo and render buffer object
  deleteBuffers();
  p->result = 1;
  return 0;
}
static XOPIORecResult
  RegisterFunction()
{
  int funcIndex;
  funcIndex = (int)GetXOPItem(0);           // Which function invoked ?
  switch (funcIndex) {
  case 0:                                   // y = RenderTriangle(w,x) (curve fitting function).
    return (XOPIORecResult)RenderTriangle;  // This function is called using the direct method.
    break;
  }
  return 0;
}
/*  XOPEntry()
This is the entry point from the host application to the XOP for all
messages after the INIT message.
*/
extern "C" void
  XOPEntry(void)
{   
  XOPIORecResult result = 0;
  switch (GetXOPMessage()) {
  case FUNCADDRS:
    result = RegisterFunction();    // This tells Igor the address of our function.
    break;
  }
  SetXOPResult(result);
}
/*  main(ioRecHandle)
This is the initial entry point at which the host application calls XOP.
The message sent by the host must be INIT.
main() does any necessary initialization and then sets the XOPEntry field of the
ioRecHandle to the address to be called for future messages.
*/
HOST_IMPORT int
  main(IORecHandle ioRecHandle)
{   
  XOPInit(ioRecHandle);                         // Do standard XOP initialization.
  SetXOPEntry(XOPEntry);                            // Set entry point for future calls.
  if (igorVersion < 600) {
    SetXOPResult(OLD_IGOR);
    return EXIT_FAILURE;
  }
  SetXOPResult(0);
  return EXIT_SUCCESS;
}