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Re: [Public WebGL] Issues while doing my last demo

On Mon, Aug 27, 2012 at 5:36 PM, Brandon Jones <tojiro@gmail.com> wrote:
I just wanted to drop in and say thanks for doing this demo! It's probably the most technically impressive WebGL usage I've seen to date, and the presentation of the different stages in addition to the very informative blog post make it a wonderful educational resource! Again, thank you!
Thanks :)
I am curious about one performance point that you didn't mention, though: many of us (yourself included) have been bemoaning the lack of MRTs to enable advanced effects such as this. Do you have any measure of how much time in your demo is spent re-rendering the same view? I'm interested to hear what the real-world benefit of MRTs would be for a technique like this.
I don't think the lack of MRTs in this demo is a big bottleneck for reasons unique to the demo:
- I only capture Albedo, Normal and Depth which can be done in 2 Passes.
- The scene is a flat, unchanging array buffer of some 60k triangles, which isn't very demanding.
- The overhead of rendering the simple scene twice is dwarfed by the performance issue of transferring the GI to the rendered scene (deferred shading with lots of overdraw) which isn't helped by the apparent lack of early-z.

If I find a way to reduce the deferred shading overhead (tiled-shading or something) and if the scene would be more expensive to draw, things would be different.