Render to texture in OpenGL ES 2.0 with iOS - ios

Question

I'm having a hard time trying to setup a render to texture environment in OpenGL ES 2.0.
What I need is a main FrameBuffer that is presented to screen and a secondary FrameBuffer that is connected to a Texture. This texture is then used in the main FrameBuffer.
I first initialize the main FrameBuffer with this code:
-(void)initializeBuffers{
//Build the main FrameBuffer
glGenFramebuffers(1, &frameBuffer);
glBindFramebuffer(GL_FRAMEBUFFER, frameBuffer);
//Build the color Buffer
glGenRenderbuffers(1, &colorBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, colorBuffer);
//setup the color buffer with the EAGLLayer (it automatically defines width and height of the buffer)
[context renderbufferStorage:GL_RENDERBUFFER fromDrawable:EAGLLayer];
glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &bufferWidth);
glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &bufferHeight);
//Attach the colorbuffer to the framebuffer
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, colorBuffer);
//Check the Framebuffer status
GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
NSAssert(status == GL_FRAMEBUFFER_COMPLETE, ERROR_FRAMEBUFFER_FAIL);
}
Then I call a function to initialise the Secondary Buffer
-(void)setupRenderToTexture{
glGenTextures(1, &gridTextureID);
glBindTexture(GL_TEXTURE_2D, gridTextureID);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, bufferWidth, bufferHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
glBindTexture(GL_TEXTURE_2D, 0);
glGenRenderbuffers(1, &textureColorBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, textureColorBuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, bufferWidth, bufferHeight);
glBindRenderbuffer(GL_RENDERBUFFER, 0);
glGenFramebuffers(1, &textureFrameBuffer);
glBindFramebuffer(GL_FRAMEBUFFER, textureFrameBuffer);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, gridTextureID, 0);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, textureColorBuffer);
GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER) ;
if(status != GL_FRAMEBUFFER_COMPLETE) {
NSLog(#"failed to make complete framebuffer object %x", status);
}else{
NSLog(#"Buffer ok");
}
glBindFramebuffer(GL_FRAMEBUFFER, 0);
}
At this point, when it is time to draw, I call a function called render that calls the function renderToTexture:
- (void)render:(CADisplayLink*)displaylink{
[self renderToTexture];
glBindBuffer(GL_FRAMEBUFFER, frameBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, colorBuffer);
glClearColor(0.0, 1.0, 0.0, 1.0);
glViewport(0, 0, bufferWidth, bufferHeight);
glClear(GL_COLOR_BUFFER_BIT);
for(GLNode *node in sceneNodes){
[node draw]; //Draw some triangles...
}
[context presentRenderbuffer:GL_RENDERBUFFER];
}
Here the renderToTexture function:
-(void)renderToTexture{
glBindFramebuffer(GL_FRAMEBUFFER, textureFrameBuffer);
glClearColor(1.0, 0.0, 0.0, 1.0);
glViewport(0, 0, bufferWidth, bufferHeight);
glClear(GL_COLOR_BUFFER_BIT);
//Render something to texture
}
If I use only the code related with the main buffer (so the functions initializeBuffers and render) the content of the main FrameBuffer is correctly displayed at screen. If I try to use the functions related with render to texture (setupRenderToTexture and renderToTexture) the main Framebuffer is no longer drawn at screen.
I wonder if this configuration has something wrong and what can I do to correct this behaviour.