FBO Blending

Newbie & Debugging Questions
#1

When I draw to the texture for my FBO, it won’t show textures behind the top texture. I read that GL_DEPTH_TEST is related to this. I tried that, but then I only was drawing the clear bit. I’ve actually already done a lot of research on this, and I’m still not finding the answer.

FBO setup:


	public void createMiniMap()
	{
	     final int WIDTH = 1600;	   
        final int HEIGHT = 900;
		
		  //frame buffer
		   int fbo;
		   int depthbuffer;
		   
	     //frame buffer
	      fbo = glGenFramebuffersEXT();
	      glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
	      
	      //depth buffer
	      depthbuffer = glGenRenderbuffersEXT();
	      glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, depthbuffer);
	      
	      //allocate space for the renderbuffer
	      glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT, WIDTH, HEIGHT);
	      
	      //attach depth buffer to fbo
	      glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, depthbuffer);
	      
	      //create texture to render to
	      miniMapTexture = glGenTextures();
	      glBindTexture(GL_TEXTURE_2D, miniMapTexture);
	      glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	      glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, WIDTH, HEIGHT, 0, GL_RGBA, GL_UNSIGNED_BYTE, (java.nio.ByteBuffer)null);
	      
	      //attach texture to the fbo
	      glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, miniMapTexture, 0);
	      
	      //check completeness
	      if(glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT) == GL_FRAMEBUFFER_COMPLETE_EXT){
	         System.out.println("Frame buffer created sucessfully.");
	      }
	      else
	         System.out.println("An error occured creating the frame buffer.");
	      
	      glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
	      
	      drawMM();
	      
	      glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
	}

draw call:


public void drawMM()
		{
		    glEnable(GL_TEXTURE_2D);
			glEnable(GL_BLEND);
			glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

			<a bunch of draw calls not likely the issue>
}

This same drawCall in regular drawing works just fine. Blending is happy. On the FBO it will only ever draw the top texture. Can anyone help?

Other resources I found interesting FWIW:
Fixing saturation with additive blending by faking HDR
glBlendFunc
FBO and Blending