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Re: [Public WebGL] frame timing and continous scaling



On Wed, Jun 3, 2015 at 9:42 AM, Florian Bösch <pyalot@gmail.com> wrote:
As an aside, I haven't witnessed requestAnimationFrame being throttled to 30 FPS by UAs. At least Chrome and Firefox on my Mac laptop will both render content with irregular frame times (resulting in the app measuring anywhere between 30 and 60 FPS) if they're GPU bound.
I can illustrate the issue when I get around to plot some frame-time charts.
I have written a tool (http://codeflow.org/issues/timing/) to measure exactly this. Here's 4 saved plots for google chrome on linux: http://codeflow.org/issues/timing/saved/google-chrome-linux.png

These plots clearly show that frame timings fall predominantly between 16.6ms and 33.3ms at the transition regions, and they also show that google Chrome somehow magically knows when to toggle. For the rising load case that could be explained by a heuristic of when chrome starts to skip frames. But for the falling load case this is a wee bit mysterious. How does chrome know the load enters a transition region coming from (throttled) 30fps and switching to 60fps unless chrome does indeed have some kind of idea how long frames take to render...