rendering framebuffer texture not working

[lookitsash]

I have read numerous articles/tutorials online regarding drawing a texture to a framebuffer in opengl, but I am having no luck getting it to work. I am creating a framebuffer, drawing a texture to the fbo, and then drawing the fbo texture to the screen but nothing displays (just a black screen). I am at a loss. If i comment out the fbo code and draw the embedded texture directly to the screen, that works. Is there some iphone specific logic that i am missing (independent of opengl)? Here is my code:

// INITIALIZATION
	glEnable(GL_TEXTURE_2D);
	glEnable(GL_BLEND);
	glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
	
	// Load Test Texture
	glGenTextures(1, &textureTest);
	glBindTexture(GL_TEXTURE_2D, textureTest);			// Bind Our Texture
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);	// Linear Filtered
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);	// Linear Filtered
	[self loadTexture: @"texture"]; // calls glTexImage2D with image data from png
	
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glViewport(0,0, 320.0f,480.0f);
	glOrthof(0,320.0f, 480.0f,0, -1.0f, 1.0f); // left, right, bottom, top
	glMatrixMode(GL_MODELVIEW);
	
	//FBO Setup
	glGenTextures(1, &textureFBO); // texture handle
	glBindTexture(GL_TEXTURE_2D, textureFBO); //bind it.
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 512, 512, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); 
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);	// Linear Filtered
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);	// Linear Filtered
	
	glGenFramebuffersOES(1, &FBO); // frame buffer 
	glBindFramebufferOES(GL_FRAMEBUFFER_OES, FBO); //bind the frame buffer
	
	// attach texture to framebuffer color buffer
	glFramebufferTexture2DOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_TEXTURE_2D, textureFBO, 0);
	if(glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES) != GL_FRAMEBUFFER_COMPLETE_OES)  printf("CANNOT CREATE FRAMEBUFFER\n");
 
 
// MAIN DRAWING LOOP
	static const Vertex3D vertices[] = {
        	{ 0.0,  100.0, 0.0},
        	{ 100.0,  100.0, 0.0},
        	{ 0.0, 200.0, 0.0},
        	{ 100.0, 200.0, 0.0}
    	};
	static const GLfloat texCoords[] = {
       		0.0, 1.0,
        	1.0, 1.0,
        	0.0, 0.0,
        	1.0, 0.0
    	};
	
	glClear(GL_COLOR_BUFFER_BIT);
	glLoadIdentity();
	
	// Render to texture
	glBindFramebufferOES(GL_FRAMEBUFFER_OES, FBO);
	
	// Draw test texture
	glBindTexture(GL_TEXTURE_2D, textureTest);
	glEnableClientState(GL_VERTEX_ARRAY);
	glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    	glVertexPointer(3, GL_FLOAT, 0, vertices);
	glTexCoordPointer(2, GL_FLOAT, 0, texCoords);
    	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
	glDisableClientState(GL_VERTEX_ARRAY);
	glDisableClientState(GL_TEXTURE_COORD_ARRAY);
	glBindTexture(GL_TEXTURE_2D, 0); //disable any bound textures.
	// End draw test texture
	
	// Render to screen
	glBindFramebufferOES(GL_FRAMEBUFFER_OES, 0); 
	
	// Draw FBO texture
	glBindTexture(GL_TEXTURE_2D, textureFBO);
	glEnableClientState(GL_VERTEX_ARRAY);
	glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    	glVertexPointer(3, GL_FLOAT, 0, vertices);
	glTexCoordPointer(2, GL_FLOAT, 0, texCoords);
	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
	glDisableClientState(GL_VERTEX_ARRAY);
	glDisableClientState(GL_TEXTURE_COORD_ARRAY);
	glBindTexture(GL_TEXTURE_2D, 0); //disable any bound textures.
	// End draw FBO texture

[jeonghyunhan]

I did experiment with RTT (render to texture) involving using FBOs so this may be useful:

// Setup FBO
glGenFramebuffersOES(1, &FBO);;
		glBindFramebufferOES(GL_FRAMEBUFFER_OES, FBO);
		glFramebufferTexture2DOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_TEXTURE_2D, textures[3], 0);
		GLuint status = glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES);
		if (status != GL_FRAMEBUFFER_COMPLETE_OES) {
			NSLog(@"Failed to generate frame buffer");
		}
		glBindFramebufferOES(GL_FRAMEBUFFER_OES, 0);

// Loop
glBindFramebufferOES(GL_FRAMEBUFFER_OES, FBO);
	glViewport(0, 0, 320, 480);
	
// Draw code
	glColorMask(0, 0, 0, 1);
	glBlendFunc(GL_ZERO, GL_SRC_ALPHA);
	glBindTexture(GL_TEXTURE_2D, textures[0]);
	[level renderHoles:q :A];
	glColorMask(1, 1, 1, 1);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
	
	glBindFramebufferOES(GL_FRAMEBUFFER_OES, 0);

[lookitsash]

I was able to resolve the issue. I never re-binded the framebuffer that draws directly to the screen:

glBindFramebufferOES(GL_FRAMEBUFFER_OES, 1);