Sign in to follow this  

Simple framebuffer is not working....driving me crazy!

This topic is 1834 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hi people. I've had a tumultuous time with framebuffers in open gl 3.3. Once, in a n engine i managed to get them to work but alas I'm having problems again.

 

My Initialisation code is as follows, pretty standard stuff:

 

bool Framebuffer::InitFramebuffer(int height,int width,GLfloat magFilter,GLfloat minFilter,bool depth)
	{
		m_height = height;
		m_width  = width;
		


		glGenTextures(1,&m_texHandle);
		glBindTexture(GL_TEXTURE_2D,m_texHandle);

		glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,minFilter);
		glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,magFilter);

		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
		

		if(!depth)
		{
			glTexImage2D(GL_TEXTURE_2D,0,GL_RGB,m_width,m_height,0,GL_RGB,GL_UNSIGNED_BYTE,NULL);
		}
		else
		{
			glTexImage2D(GL_TEXTURE_2D,0,GL_DEPTH_COMPONENT24,m_width,m_height,0,GL_DEPTH_COMPONENT,GL_UNSIGNED_BYTE,NULL);
		}


		glGenFramebuffers(1,&m_FBOhandle);
		glBindFramebuffer(GL_FRAMEBUFFER,m_FBOhandle);

		glGenRenderbuffers(1,&m_depthHandle);
		glBindRenderbuffer(GL_RENDERBUFFER,m_depthHandle);

		glRenderbufferStorage(GL_RENDERBUFFER,GL_DEPTH_COMPONENT24,m_width,m_height);

		glFramebufferRenderbuffer(GL_FRAMEBUFFER,GL_DEPTH_ATTACHMENT,GL_RENDERBUFFER,m_depthHandle);


		if(!depth)
		{
			glFramebufferTexture2D(GL_FRAMEBUFFER,GL_COLOR_ATTACHMENT0,GL_TEXTURE_2D,fbo->GetTextureHandle(),0);
			GLenum drawBufs[] = {GL_COLOR_ATTACHMENT0};
			glDrawBuffers(1,drawBufs);
		}
		else
		{
			glFramebufferTexture(GL_FRAMEBUFFER,GL_DEPTH_ATTACHMENT,m_texHandle,0);
			glDrawBuffer(GL_NONE);
			glReadBuffer(GL_NONE);
		}

		
		

		 if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
		 {
			 std::cout<<"problem with framebuffer!";
			 return false;
		 }
		 else
		 {
			 std::cout<<"framebuffer ok! :)";
		 }

	    glBindFramebuffer(GL_FRAMEBUFFER,0);
		
		return true;
	}

 

The status check at the end is always ok. In the calling code I render a texture to a full screen quad and consequently to the framebuffer, and then try and render this stored texture to a full screen quad again, just a simple test. I've even run the code in gDebugger gl and checked the texture contents at runtime - the fb texture is a solid black. Please help me!

 

               glBindFramebuffer(GL_FRAMEBUFFER,fbo->GetFrameBufferHandle());
		  glViewport(0,0,512,512);
		  glUseProgram(test->GetHandle());
		  glBindTexture(GL_TEXTURE_2D,myTex->m_handle);
		  test->SetUniform("tex",0);
		  quad->Draw();
		  //render text
		glBindFramebuffer(GL_FRAMEBUFFER,0);

		 //glUseProgram(test->GetHandle());
		 glBindTexture(GL_TEXTURE_2D,fbo->GetTextureHandle());
		 test->SetUniform("tex",0);
		 quad->Draw();

		
		glfwSwapBuffers();

 

 

Share this post


Link to post
Share on other sites
So I am assuming your FBO is 100% OK so problem will be elsewhere..
Well I'm not sure if this is your problem but there should be several things to chcek:
- from the code I can see that you unbind frambuffer using glBindFramebuffer(GL_FRAMEBUFFER,0); so you are rendering to nothing
- another thing to check is if you are not trying to render to texture which is also source texture (single texture for multiple FBO )
- last thing to check is clearing your FBO before render / disabling depth test if used Edited by SaTANO

Share this post


Link to post
Share on other sites

Thanks for your reply. I'm unbinding the framebuffer AFTER rendering the scene, so it should be rendered. In fact, now in gDebugger I can see a texture being rendered IF i draw an immediate mode triangle to the screen, as a simple test.

 

However, even if I bind this texture using the handle in the FB initialisation I cannot render it to the screen! I will now try with a few more different scenarios.

 

For some reason though, the FBO is still not rendered to if I try to 'capture' a full screen quad.

Share this post


Link to post
Share on other sites

Have you tried clearing the appropriate buffer bits before rendering to FBO? Also check to see that the renderbuffer is black as well - when I used renderbuffers last I originally had an issue where the renderbuffer would have a valid texture but my FBO was solid black. Also, after glTexImage2D(), make sure to call glBindTexture(GL_TEXTURE_2D, 0);.

 

Edit: I believe the renderbuffer also needs unbound after glRenderbufferStorage()

Edited by Anfractu0us

Share this post


Link to post
Share on other sites
Sign in to follow this