GL_INVALID_OPERATION at glFramebufferTexture2DEXT

[Christian Knudsen]

I'm trying to get a basic FBO up and running, but I'm getting a GL_INVALID_OPERATION error when trying to assign a texture to the FBO. I'm on WindowsXP and am programming in Freepascal with SDL as the context wrapper. Here's a code snippet:

   glEnable(GL_TEXTURE_2D);
   glClearColor(0.0, 0.0, 0.0, 0.0);
   glViewport(0, 0, 800, 600);
   glClear(GL_COLOR_BUFFER_BIT);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(0.0, 800, 600, 0.0, -1.0, 1.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   glEnable(GL_BLEND);
   glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
   glDisable(GL_LIGHTING);
   glShadeModel(GL_SMOOTH);

[...]

   TempSurface := IMG_Load('gfx/logo.png');
   glGenTextures(1, @TexID);
   glBindTexture(GL_TEXTURE_2D, TexID);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
   glTexImage2D(GL_TEXTURE_2D, 0, 4, 512, 512, 0, GL_RGBA, GL_UNSIGNED_BYTE, TempSurface^.pixels);
   SDL_FreeSurface(TempSurface);

[...]

   IF glext_LoadExtension('GL_EXT_framebuffer_object') THEN BEGIN
      glGenFramebuffersEXT(1, @FBO);
      glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, FBO);
// NO ERROR HERE
      glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, TexID, 0);
// GL_INVALID_OPERATION RETURNED HERE!
      glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
   END;

I can't figure out what I'm doing wrong here...

[Christian Knudsen]

It was the texture's internal format. I had to change it to GL_RGBA instead of 4.