Question

I’ve been struggling with this for a while now, and this code crashes with, to me, unknown reasons. I’m creating an FBO, binding a texture, and then the very first glDrawArrays() crashes with a “EXC_BAD_ACCESS” on my iPhone Simulator.

Here’s the code I use to create the FBO (and bind texture and…)

glGenFramebuffers(1, &lastFrameBuffer);
glGenRenderbuffers(1, &lastFrameDepthBuffer);
glGenTextures(1, &lastFrameTexture);

glBindTexture(GL_TEXTURE1, lastFrameTexture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 768, 1029, 0, GL_RGBA, GL_UNSIGNED_SHORT_5_6_5, NULL);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

//Bind/alloc depthbuf
glBindRenderbuffer(GL_RENDERBUFFER, lastFrameDepthBuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, 768, 1029);

glBindFramebuffer(GL_FRAMEBUFFER, lastFrameBuffer);

//binding the texture to the FBO :D
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, lastFrameTexture, 0);

// attach the renderbuffer to depth attachment point
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, lastFrameDepthBuffer);

[self checkFramebufferStatus];

As you can see this takes part in an object, checkFrameBufferStatus looks like this:

GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
switch(status)
{
  case GL_FRAMEBUFFER_COMPLETE:
    JNLogString(@"Framebuffer complete.");
    return TRUE;

  case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT:
    JNLogString(@"[ERROR] Framebuffer incomplete: Attachment is NOT complete.");
    return false;

  case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT:
    JNLogString(@"[ERROR] Framebuffer incomplete: No image is attached to FBO.");
    return false;

  case GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS:
    JNLogString(@"[ERROR] Framebuffer incomplete: Attached images have different dimensions.");
    return false;

  case GL_FRAMEBUFFER_UNSUPPORTED:
    JNLogString(@"[ERROR] Unsupported by FBO implementation.");
    return false;

   default:
    JNLogString(@"[ERROR] Unknown error.");
    return false;

JNLogString is just an NSLog, and in this case it gives me:

2010-04-03 02:46:54.854 Bubbleeh[6634:207] ES2Renderer.m:372 [ERROR] Unknown error.

When I call it right there.

So, it crashes, and diagnostic tells me there’s an unknown error and I’m kinda stuck. I basically copied the code from the OpenGL ES 2.0 Programming Guide…

What am I doing wrong?

Answer 1

        glBindTexture(GL_TEXTURE1, lastFrameTexture);

That’s not allowed, I was trying to bind the texture to unit one (GL_TEXTURE1), but that should be done by glActiveTexture(), not by glBindTexture(), which wants to know the type of the texture (GL_TEXTURE_2D, GL_TEXTURE_3D, etc.) not the texture unit. To place a texture in texture unit 1 I now have the following code which I think is correct:

//Bind 2D Texture lastFrameTexture to texture unit 1
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, lastFrameTexture);