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Re: [Public WebGL] The state of MRTs



On Tue, Mar 27, 2012 at 9:38 PM, Gregg Tavares (å) <gman@google.com> wrote:
All devices currently support MRT. Low end devices support N render targets where N = 1.
For some weird reason OpenGL ES choose not to forward-compatible the FBO featureset by allowing for N>1 rendertargets. I don't understand why that was done this way, if it hadn't been, we could get a clear picture now what mobile devices actually support MRT and they would not have to discuss/ratify another set of extensions for ES. Any insight as to what the ES-WG plan in regards to MRT would be, would be appreciated.

MRT was introduced in 2003, over 9 years ago. It's been used nearly every PC game since Half Life 2. Getting more adoption by top game developers means adding more features they need to make their games.Â
This problem won't go away ever. Waiting a year or 2 years, or 5 years won't change the fact that there will always be devices where MAX_COLOR_ATTACHMENTS is less than other devices.
With a support rate around 80%, everybody on desktops has to do an alternative renderingpath to MRTs anway. But that number isn't gonna go down. 2 or 5 years from now, not only will the problem not go away, it will be worse, because 2-5 years from now 98% of desktops will have MRT support. If you do it now, like right now, it's the least pain you're ever gonna get, the pain's not gonna get any smaller by any amount of waiting.

MRT is a perf improvement. A huge one.
I do actually think that MRT support is a bigger boon to mobile devices than to desktops. Desktops often do have enough juice to simply render a scene multiple times. Doing the same on mobiles is disproportionally more expensive because they have far less GPU power. So speeding up techniques that require multiple outputs (like normal, depth, color, specularity etc.) is a disproportional advantage in mobiles.