title: GLSL gl_FragDepth equivalent in Metal shaders
body: <p>I'm looking to adjust a fragments depth in a Metal shader. Previously I was achieving this via GLSL's built-in output variable <a href="https://www.khronos.org/opengl/wiki/Fragment_Shader/Defined_Outputs" rel="nofollow noreferrer">gl_FragDepth</a>. Is there an equivalent approach using Apple's Metal shaders on iOS?</p>