So I am trying to use a stencil buffer in iOS for masking/clipping purposes. Do you guys have any idea why this code may not work? This is everything I have associated with Stencils. On iOS 4 I get a black screen. On iOS 5 I get exactly what I expect. The transparent areas of the image I drew in the stencil are the only areas being drawn later. Code is below. This is where I setup the frameBuffer, depth and stencil. In iOS the depth and stencil are combined. -(void)setupDepthBuffer { glGenRenderbuffers(1, &depthRenderBuffer); glBindRenderbuffer(GL_RENDERBUFFER, depthRenderBuffer); glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8_OES, self.frame.size.width * [[UIScreen mainScreen] scale], self.frame.size.height * [[UIScreen mainScreen] scale]); } -(void)setupFrameBuffer { glGenFramebuffers(1, &frameBuffer); glBindFramebuffer(GL_FRAMEBUFFER, frameBuffer); glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, colorRenderBuffer); glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthRenderBuffer); glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, depthRenderBuffer); // Check the FBO. if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) { NSLog(@"Failure with framebuffer generation: %d", glCheckFramebufferStatus(GL_FRAMEBUFFER)); } } This is how I am setting up and drawing the stencil. (Shader code below.) glEnable(GL_STENCIL_TEST); glDisable(GL_DEPTH_TEST); glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE); glDepthMask(GL_FALSE); glStencilFunc(GL_ALWAYS, 1, -1); glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE); glColorMask(0, 0, 0, 0); glClear(GL_STENCIL_BUFFER_BIT); machineForeground.shader = [StencilEffect sharedInstance]; [machineForeground draw]; machineForeground.shader = [BasicEffect sharedInstance]; glDisable(GL_STENCIL_TEST); glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE); glDepthMask(GL_TRUE); Here is where I am using the stencil. glEnable(GL_STENCIL_TEST); glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP); glStencilFunc(GL_EQUAL, 1, -1); ...Draw Stuff here glDisable(GL_STENCIL_TEST); Finally here is my fragment shader. varying lowp vec2 TexCoordOut; uniform sampler2D Texture; void main(void) { lowp vec4 color = texture2D(Texture, TexCoordOut); if(color.a < 0.1) gl_FragColor = color; else discard; }