src/gl/fbo.c

#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
#include <assert.h>
#include "system-gl.h"

#include "fbo.h"

fbo_t * fbo_new()
{
  fbo_t * fbo = malloc (sizeof(fbo_t));
  fbo->fbo_id = 0;
  fbo->old_fbo_id = 0;
  fbo->renderbuf_id = 0;
  fbo->depthbuf_id = 0;
  return fbo;
}

bool use_ext()
{
  // do we need to use the EXT or ARB version?
  return (!glewIsSupported("GL_ARB_framebuffer_object") &&
	  glewIsSupported("GL_EXT_framebuffer_object"));
}

bool check_fbo_status()
{
  /* This code is based on user V-man code from
     http://www.opengl.org/wiki/GL_EXT_framebuffer_multisample
     See also: http://www.songho.ca/opengl/gl_fbo.html */
  GLenum status;
  bool result = false;
  if (use_ext()) {
    status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
  }
  else {
    status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
  }

  if (report_glerror("checking framebuffer status")) return false;

  if (status == GL_FRAMEBUFFER_COMPLETE) {
    result = true;
  }
  else if (status == GL_FRAMEBUFFER_UNSUPPORTED) {
    fprintf (stderr, "GL_FRAMEBUFFER_UNSUPPORTED\n");
  }
  else if (status == GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT) {
    fprintf (stderr, "GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT\n");
  }
  else if (status == GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT) {
    fprintf (stderr, "GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT\n");
  }
  else if (status == GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT) {
    fprintf (stderr, "GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT\n");
  }
  else if (status == GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT) {
    fprintf (stderr, "GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT\n");
  }
  else if (status == GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT) {
    fprintf (stderr, "GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT\n");
  }
  else if (status == GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT) {
    fprintf (stderr, "GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT\n");
  }
  else if (status == GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE_EXT) {
    fprintf (stderr, "GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE_EXT\n");
  }
  else {
    fprintf (stderr, "Unknown Code: glCheckFramebufferStatusEXT returned: %d\n",
	     status);
  }
  return result;
}

bool fbo_ext_init(fbo_t *fbo, size_t width, size_t height)
{
  // Generate and bind FBO
  glGenFramebuffersEXT(1, &fbo->fbo_id);
  if (report_glerror("glGenFramebuffersEXT")) return false;
  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo->fbo_id);
  if (report_glerror("glBindFramebufferEXT")) return false;

  // Generate depth and render buffers
  glGenRenderbuffersEXT(1, &fbo->depthbuf_id);
  glGenRenderbuffersEXT(1, &fbo->renderbuf_id);

  // Create buffers with correct size
  if (!fbo_resize(fbo, width, height)) return false;

  // Attach render and depth buffers
  glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, 
                               GL_RENDERBUFFER_EXT, fbo->renderbuf_id);
  if (report_glerror("specifying color render buffer EXT")) return false;


  if (!check_fbo_status()) {
    fprintf (stderr, "Problem with OpenGL EXT framebuffer"
	     " after specifying color render buffer.\n");
    return false;
  }

  if (glewIsSupported("GL_EXT_packed_depth_stencil")) {
    glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT,
				 GL_RENDERBUFFER_EXT, fbo->depthbuf_id);
    if (report_glerror("specifying depth render buffer EXT")) return false;

    glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_STENCIL_ATTACHMENT_EXT,
				 GL_RENDERBUFFER_EXT, fbo->depthbuf_id);
    if (report_glerror("specifying stencil render buffer EXT")) return false;
		
    if (!check_fbo_status()) {
      fprintf (stderr,
	       "Problem with OpenGL EXT framebuffer after"
	       " specifying depth render buffer.\n");
      return false;
    }
  }
  else {
    fprintf (stderr,
	     "Warning: Cannot create stencil buffer "
	     "(GL_EXT_packed_depth_stencil not supported)\n");
    glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, 
				 GL_RENDERBUFFER_EXT, fbo->depthbuf_id);
    if (report_glerror("specifying depth render buffer EXT")) return false;
		
    if (!check_fbo_status()) {
      fprintf (stderr,
	       "Problem with OpenGL EXT framebuffer "
	       "after specifying depth stencil render buffer.\n");
      return false;
    }
  }

  return true;
}

bool fbo_arb_init(fbo_t *fbo, size_t width, size_t height)
{
  // Generate and bind FBO
  glGenFramebuffers(1, &fbo->fbo_id);
  if (report_glerror("glGenFramebuffers")) return false;
  glBindFramebuffer(GL_FRAMEBUFFER, fbo->fbo_id);
  if (report_glerror("glBindFramebuffer")) return false;

  // Generate depth and render buffers
  glGenRenderbuffers(1, &fbo->depthbuf_id);
  glGenRenderbuffers(1, &fbo->renderbuf_id);

  // Create buffers with correct size
  if (!fbo_resize(fbo, width, height)) return false;

  // Attach render and depth buffers
  glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, 
			    GL_RENDERBUFFER, fbo->renderbuf_id);
  if (report_glerror("specifying color render buffer")) return false;

  if (!check_fbo_status()) {
    fprintf (stderr, "Problem with OpenGL framebuffer after "
	     "specifying color render buffer.\n");
    return false;
  }

  //glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, 
  // to prevent Mesa's software renderer from crashing, do this in two stages. 
  // ie. instead of using GL_DEPTH_STENCIL_ATTACHMENT, do DEPTH then STENCIL. 
  glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT,
			    GL_RENDERBUFFER, fbo->depthbuf_id);
  glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, 
			    GL_RENDERBUFFER, fbo->depthbuf_id);
  if (report_glerror("specifying depth stencil render buffer")) return false;

  if (!check_fbo_status()) {
    fprintf (stderr, "Problem with OpenGL framebuffer after "
	     "specifying depth render buffer.\n");
    return false;
  }

  return true;
}


bool fbo_init(fbo_t *fbo, size_t width, size_t height)
{
  /*
    Some OpenGL drivers include the framebuffer functions but not with
    core or ARB names, only with the EXT name. This has been worked-around
    by deciding at runtime, using GLEW, which version needs to be used. See also:
  
    http://www.opengl.org/wiki/Framebuffer_Object
    http://stackoverflow.com/questions/6912988/glgenframebuffers-or-glgenframebuffersex
    http://www.devmaster.net/forums/showthread.php?t=10967
  */

  bool result = false;
  if (glewIsSupported("GL_ARB_framebuffer_object")) {
    result = fbo_arb_init(fbo, width, height);
  }
  else if (use_ext()) {
    result = fbo_ext_init(fbo, width, height);
  }
  else {
    fprintf (stderr, "Framebuffer Object extension not found by GLEW\n");
  }
  return result;
}

bool fbo_resize(fbo_t *fbo, size_t width, size_t height)
{
  if (use_ext()) {
    glBindRenderbufferEXT(GL_RENDERBUFFER, fbo->depthbuf_id);
    if (glewIsSupported("GL_EXT_packed_depth_stencil")) {
      glRenderbufferStorageEXT(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, width, height);
      if (report_glerror("creating EXT depth stencil render buffer")) return false;
    }
    else {
      glRenderbufferStorageEXT(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, width, height);
      if (report_glerror("creating EXT depth render buffer")) return false;
    }

    glBindRenderbufferEXT(GL_RENDERBUFFER, fbo->renderbuf_id);
    glRenderbufferStorageEXT(GL_RENDERBUFFER, GL_RGBA8, width, height);
    if (report_glerror("creating EXT color render buffer")) return false;
  } else {
    glBindRenderbuffer(GL_RENDERBUFFER, fbo->renderbuf_id);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA8, width, height);
    if (report_glerror("creating color render buffer")) return false;

    glBindRenderbuffer(GL_RENDERBUFFER, fbo->depthbuf_id);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, width, height);
    if (report_glerror("creating depth stencil render buffer")) return false;

  }

  return true;
}

void fbo_delete(fbo_t *fbo)
{
  free (fbo);
}

GLuint fbo_bind(fbo_t *fbo)
{
  glGetIntegerv(GL_FRAMEBUFFER_BINDING, (GLint *)(&fbo->old_fbo_id));
  if (use_ext()) {
    glBindFramebufferEXT(GL_FRAMEBUFFER, fbo->fbo_id);
  }
  else {
    glBindFramebuffer(GL_FRAMEBUFFER, fbo->fbo_id);
  }
  return fbo->old_fbo_id;
}

void fbo_unbind(fbo_t *fbo)
{
  if (use_ext()) {
    glBindFramebufferEXT(GL_FRAMEBUFFER, fbo->old_fbo_id);
  }
  else {
    glBindFramebuffer(GL_FRAMEBUFFER, fbo->old_fbo_id);
  }
}

bool report_glerror(const char * function)
{
  GLenum tGLErr = glGetError();
  if (tGLErr != GL_NO_ERROR) {
    fprintf (stderr, "OpenGL error %04x after %s\n", tGLErr, function);
    return true;
  }
  return false;
}