Is it possible to make an OpenGL ES layer transparent?

Question

Is it possible to make the background of an OpenGL ES layer transparent so you can see what is behind the OpenGL ES content?

Answer 1

You have to do two things:

1. When you initialize your CAEAGLLayer, set the opaque property to NO (or FALSE).
   
   You may also need to make sure your drawableProperties uses a color format that supports transparency (kEAGLColorFormatRGBA8 does, but kEAGLColorFormatRGB565 does not).
   
   eaglLayer.opaque = NO;

eaglLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:NO], kEAGLDrawablePropertyRetainedBacking, kEAGLColorFormatRGBA8, kEAGLDrawablePropertyColorFormat, nil];
   
   If you are using XCode's OpenGL project template, this will be in [EAGLView's initWithCoder].
   
   
2. Draw the background in a transparent color and alpha.
   
   glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
   
   If you are using XCode's OpenGL project template, this will be in the "render" methods: [ES1Renderer render] and [ES2Renderer render].