Minimal example for creating FBO using OpenGL ES 2.0 on iOS

I am having trouble creating an FBO, and then using that as a texture in my iOS app. I've uploaded a stripped down version of my app on github, which shows the problem. I get just a blank screen with a weird color which I never set. Checking status shows that the FBO was created successfully. https://github.com/glman74/simpleFBO I have already looked at related stackoverflow questions, and specifically the link below from datenwolf which shows how to set up an FBO using GLUT, but does not use shaders. I am still not sure what I am doing wrong. https://github.com/datenwolf/codesamples/blob/master/samples/OpenGL/minimalfbo/ I am also appending here relevant parts of the code. In the renderFBO method, I am just doing a clear. I would have expected that this solid colored (green) texture would be used when I am rendering the polygon in the main render. FBO setup: ``` // intialize FBO - (void)setupFBO { fbo_width = 512; fbo_height = 512; glGenFramebuffers(1, &fboHandle); glGenTextures(1, &fboTex); glGenRenderbuffers(1, &depthBuffer); glBindFramebuffer(GL_FRAMEBUFFER, fboHandle); glBindTexture(GL_TEXTURE_2D, fboTex); glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, fbo_width, fbo_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER_APPLE, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, fboTex, 0); glBindRenderbuffer(GL_RENDERBUFFER, depthBuffer); glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24_OES, fbo_width, fbo_height); glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER_APPLE, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthBuffer); // FBO status check GLenum status; status = glCheckFramebufferStatus(GL_FRAMEBUFFER); switch(status) { case GL_FRAMEBUFFER_COMPLETE: NSLog(@"fbo complete"); break; case GL_FRAMEBUFFER_UNSUPPORTED: NSLog(@"fbo unsupported"); break; default: /* programming error; will fail on all hardware */ NSLog(@"Framebuffer Error"); break; } glBindFramebuffer(GL_FRAMEBUFFER, 0); } ``` FBO render: ``` // render FBO - (void)renderFBO { glBindTexture(GL_TEXTURE_2D, 0); glEnable(GL_TEXTURE_2D); glBindFramebuffer(GL_FRAMEBUFFER, fboHandle); glViewport(0,0, fbo_width, fbo_height); glClearColor(0.0f, 1.0f, 0.0f, 1.0f); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glBindFramebuffer(GL_FRAMEBUFFER, 0); } ``` Main Render: ``` - (void)glkView:(GLKView *)view drawInRect:(CGRect)rect { // render FBO tex [self renderFBO]; glViewport(0, 0, self.view.bounds.size.width, self.view.bounds.size.height); // render main glClearColor(0.65f, 0.65f, 0.65f, 1.0f); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnable(GL_TEXTURE_2D); glActiveTexture(GL_TEXTURE0); glUniform1i(uSamplerLoc, 0); // Render glUseProgram(_program); glUniformMatrix4fv(uniforms[UNIFORM_MODELVIEWPROJECTION_MATRIX], 1, 0, _modelViewProjectionMatrix.m); glUniformMatrix3fv(uniforms[UNIFORM_NORMAL_MATRIX], 1, 0, _normalMatrix.m); glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); glDisable(GL_TEXTURE_2D); } ``` An ideas on what I might be doing wrong? Edit #1: I have made some small changes to my code at github. Tried using GL_FRAMEBUFFER instead of GL_DRAW_FRAMEBUFFER_APPLE above. Also added a bind texture call, which was missing. Still doesn't work. Edit #2: I found a solution. I needed to call in main render: ``` // reset to main framebuffer [((GLKView *) self.view) bindDrawable]; ```