3 replies to this topic

[ic0de]

I'm trying to add MSAA to my OpenGL game but for some reason it's not working. I have two FBO's, one of them is multisampled and one is not. They both have Two color attachments and one depth attachment. Each frame the multisampled one is blitted onto the non multisampled one. The problem is that the multisampling doesn't seem to have any effect, still lots of aliasing, I thing something is broken. Here is relevant code:

FBO setup:

void fbuffer::create(bool mrt, bool hdr, bool depth, bool multisample, int samples, bool noColour)
{
if(hdr)
{
  colorFormat = GL_HALF_FLOAT_ARB;
  format = GL_RGBA16F_ARB;
}
else
{
  colorFormat = GL_UNSIGNED_BYTE;
}
glGenFramebuffersEXT(1, &fbo);
glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER_EXT, fbo);
  glGenTextures(1, &texture);
  glBindTexture(GL_TEXTURE_2D, texture);
  glTexImage2D(GL_TEXTURE_2D, 0, format, screenw, screenh, 0, GL_RGBA, colorFormat, NULL);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glGenRenderbuffersEXT(1, &rboColour);
  glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, rboColour);
  if(GLEW_EXT_framebuffer_multisample && multisample)
  {
   glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER_EXT, samples, format, screenw, screenh);
  }
  else
  {
   glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, format, screenw, screenh);
  }
  glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_RENDERBUFFER_EXT, rboColour);
  glFramebufferTexture2DEXT(GL_DRAW_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, texture, 0);
if(mrt)
{
  glGenTextures(1, &texture2);
  glBindTexture(GL_TEXTURE_2D, texture2);
  glTexImage2D(GL_TEXTURE_2D, 0, format, screenw, screenh, 0, GL_RGBA, colorFormat, NULL);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glGenRenderbuffersEXT(1, &rboColour2);
  glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, rboColour2);
  if(GLEW_EXT_framebuffer_multisample && multisample)
  {
   glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER_EXT, samples, format, screenw, screenh);
  }
  else
  {
   glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, format, screenw, screenh);
  }
  glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT1_EXT, GL_RENDERBUFFER_EXT, rboColour2);
  glFramebufferTexture2DEXT(GL_DRAW_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT1_EXT, GL_TEXTURE_2D, texture2, 0);
}
if(depth)
{
  glGenTextures(1, &depthtex);
  glBindTexture(GL_TEXTURE_2D, depthtex);
  glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, screenw, screenh, 0, GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, NULL);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glGenRenderbuffersEXT(1, &rboDepth);
  glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, rboDepth);
  if(GLEW_EXT_framebuffer_multisample && multisample)
  {
   glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER_EXT, samples, GL_DEPTH_COMPONENT, screenw, screenh);
  }
  else
  {
   glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT, screenw, screenh);
  }
  glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, rboDepth);
  glFramebufferTexture2DEXT(GL_DRAW_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_TEXTURE_2D, depthtex, 0);
}
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
glBindTexture(GL_TEXTURE_2D, 0);
}
void fbuffer::bind()
{
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
}

creating the objects:

  msbuffer.format = screen->format->BytesPerPixel;
  msbuffer.screenw = screen->w;
  msbuffer.screenh = screen->h;
  msbuffer.create(true, true, true, true, 8, false);
  fbo1.format = screen->format->BytesPerPixel;
  fbo1.screenw = screen->w;
  fbo1.screenh = screen->h;
  fbo1.create(true, true, true, false, 1, false);

blitting the buffers:

  glBindFramebufferEXT(GL_READ_FRAMEBUFFER_EXT, msbuffer.fbo);
  glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER_EXT, fbo1.fbo);
  glBlitFramebufferEXT(0, 0, screen->w, screen->h, 0, 0, screen->w, screen->h, GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT, GL_NEAREST);
  fbo1.bind();

Anyone know what I'm doing wrong?

[theagentd]

You shouldn't have to blit the depth buffer. Resolved depth is practically worthless. What hardware are you running on? Maybe you've forced antialiasing to off in your drivers? Exactly what is aliased? MSAA does nothing to improve shader aliasing.

[ic0de]

You shouldn't have to blit the depth buffer. Resolved depth is practically worthless. What hardware are you running on? Maybe you've forced antialiasing to off in your drivers? Exactly what is aliased? MSAA does nothing to improve shader aliasing.

I'm running on an Nvidia GTX 460, the aliased part is around the edges of objects. I suppose I should also check my driver settings.

[ic0de]

I fixed it, I don't know why but I needed to create the fbos without attaching any textures to them.