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Thread: Low fps even on empty canvas.

  1. #31

    Re: Low fps even on empty canvas.

    Ive never seen AA work at all (either browser win/linux) but Im not really too fussed ATM this will eventually come.
    On a related note I'ld like to see better AF, looking at whats onscreen looks like 1xAF

    The problem with benchmarking right now is that the performance depends rather drastically on the application.
    true there are a few more factors to worry about, but its always been thus eg PC games are CPU/GPU limited (fillrate,shader speed etc bottlenecked). My point is once webgl goes mainstream we will see websites benchmarking Application X/Y with browser A vs browser B vs browser C (even internet explorer might join the party ). This will drive the browser makers to drastically improve their overall performances. Honestly I expect within a year for performance to be 10x better than it is now

  2. #32
    Senior Member
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    Re: Low fps even on empty canvas.

    The benchmarking problem for WebGL is even worse than for PC games though - we have to factor in the performance of the JavaScript engine and also the WebGL/ANGLE layers and performance of the compositing engine. That's at least three more variables than we'd have to judge for Direct3D or OpenGL implementations alone.

    AF? Anisotropic filtering? I don't think that's supported in OpenGLES without an extension - so it's not in WebGL right now.

  3. #33

    Re: Low fps even on empty canvas.

    cheers Steve yes Anisotropic filtering, Im doing a platformer ATM, thus all those glancing? (whats the word) platforms/walls look crap without AF.
    ATM as the OP saiz 'Low fps even on empty canvas.' atm it seems the compositing is the main bottleneck

  4. #34
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    Re: Low fps even on empty canvas.

    Maybe the --enable-accelerated-compositing flag could help in chrome?

    https://sites.google.com/a/chromium.org ... -in-chrome

    aloha

  5. #35
    Senior Member
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    Re: Low fps even on empty canvas.

    Quote Originally Posted by zed
    cheers Steve yes Anisotropic filtering, Im doing a platformer ATM, thus all those glancing? (whats the word) platforms/walls look crap without AF.
    ATM as the OP saiz 'Low fps even on empty canvas.' atm it seems the compositing is the main bottleneck
    The compositing issue is gradually getting fixed - the developers know it's a problem...but it's not such a simple thing to change.

    When you know the orientation of the surface to the camera (as is often the case in a platformer where the camera doesn't roll or pitch much) - you can change the texture to make that glancing angle problem much less. The reason there is a problem is because the hardware for MIPmapping has to pick the worst case texture 'compression' and prevent that from aliassing - so (for example) on a wall where the U direction of the texture runs along the length of the wall and the V direction is vertical - the most common problem is when the U axis is compressed and the V isn't...the reverse is almost never the case for "normal" camera angles - right? So if you make the texture much bigger in the V direction than in the U (so instead of having...say...a 128x128 map, you go with a 128x512) - then when the U-direction compression drops the MIPmap level to (say) the third MIP map then instead of sampling a 16x16 map, it'll be sampling a 16x64 - which will be much less blurry in the vertical direction.

    Simply increasing the resolution of the map in BOTH directions won't help - if you had (say) a 512x512 map being viewed under similar circumstances, then the U-direction compression would still result in a 32x32 map being viewed. Ironically, a 128x512 map actually looks better than a 512x512 map under these circumstances!

    That's so strongly counter-intuitive that you'll want to do the experiment to convince yourself that it works.

    Only when the "shape" of the map (the width-to-height ratio) is a good match for the worst case viewing angle do you avoid this problem. In effect, you are pre-filtering your map and thereby avoiding the hardware filtering it for you!

    Of course in the case of floor and ceiling textures, unless you are in a long thin corridor, you don't know whether it'll be the U or the V direction that is compressed - so you can't get this trick to work. However, you could consider making two different textures - one compressed in the U direction and the other compressed in V and switching between them depending on whether the camera is pointing north-south or east-west.

    This technique leads to a more general solution called "RIPmapping" (rectangular MIPmapping) - but to do that properly requires hardware support - and these days, true anisotropic filtering is preferred. However, in constrained circumstances - and without that hardware support - this trick definitely helps!

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