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Re: [Public WebGL] Implement extension EXT_frag_depth in WebGL

On Tue, Dec 4, 2012 at 3:15 AM, Mark Callow <callow.mark@artspark.co.jp> wrote:

I don't know what gave you that idea. OpenGL 3.0 was released in August 2008, OpenGL ES 2.0 in March 2007.  Clearly it is based on OpenGL 2.0.
Well even more mysterious then, since OpenGL 2.0 had frag depth for half a decade before ES copied the API (but not this functionality)
I don't think the vendors have any interest in keeping features concealed. If it was in the hardware they would advertise the extension.  
If you can call "discard" in a shader then the hardware/driver must have a path that excludes early-z as well as a conditional on the depth write. I just find it unlikely that you'd have an early-z switch and depth write conditional, but no way to set the depth value.