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Re: [Public WebGL] Implement extension EXT_frag_depth in WebGL

On Mon, Dec 3, 2012 at 7:12 PM, Kenneth Russell <kbr@google.com> wrote:
Slight concern that it seems to be supported on
very few mobile devices.
I find that odd as well. Especially given that ES 2.0 was modelled after OGL 3.0 which has included that capability for nearly a decade. But I wouldn't be concerned about it for two reasons really:
1) It's coming anyway with ES 3.0 and presumably as vendors start supporting ES 3.0 support will go up.
2) I have a hard time imagining that it's actually absent in the hardware (after all it has been core part of any programmable hardware since a decade). I suspect it's just not exposed by the driver. So most likely vendors can provide a lot of support with a firmware update.

Given that depth writes are not free (they abort early-z), techniques which use depth writes are nearly all in the category of high performance optimizations. It's unlikely those matter much on mobiles.