Re: [Public WebGL] Proper way of rendering only when something changes

https://tools.google.com/dlpage/chromesxs

On Mon, Jun 4, 2012 at 12:27 AM, Mikko Mononen <mikko@tinkercad.com> wrote:

Hi,

I'm still waiting for confirmation on the FF bug, this might actually
be Chrome bug. Sorry for communicating otherwise.

Here's a quick JSfiddle to show how our rendering looks like:
http://jsfiddle.net/MikkoMononen/S2vt8/2/

Unfortunately that example does not trigger the bug, but it should
give and idea what I'm doing. I have to see if rendering something
will actually trigger the situation (where's imm mode when you need
it!).

If I disable draw2() in our codebase or move call to draw2() it to the
beginning of draw(), the problem goes away.

So it looks like that if the last thing I did was to render to an
off-screen buffer and then the browser needs to render/composite the
page again (sorry my understanding of dom/render/composite updates is
a bit vague here), the WebGL canvas is rendered blank.

Adding preserveDrawingBuffer does not help.

--mikko

On Sun, Jun 3, 2012 at 11:51 AM, Ilmari Heikkinen
<ilmari.heikkinen@gmail.com> wrote:
> Hi Mikko,
>
> In what cases does the unprompted WebGL canvas clearing occur? Do you
> have a minimal testcase and/or more details about the hardware setup
> of your users.
>
> The only canvas-clearing DOM thing that I'm aware of is setting the
> canvas element width and height attributes. If the clearing happens on
> CSS changes or changing unrelated elements, it sounds like a browser
> bug so all details would be appreciated.
>
> Thanks,
> Ilmari
>
>
> 2012/6/1 Mikko Mononen <mikko@tinkercad.com>:
>>
>> Hi,
>>
>> Are there some general guidelines how to build a render loop where the
>> app only draws the scene when something changes? Pretty much all the
>> samples out there render in an infinite loop.
>>
>> Our app currently renders only when something changes to save the
>> precious battery and fans. We're getting increasing amount of reports
>> from the users using bleeding edge Firefox or Chrome that rendering
>> does not work for them anymore. If we render stuff with infinite loop
>> using requestAnimationFrame(), everything works, but once rendering
>> only when stuff changes, the WenGL canvas is cleared when any element
>> state changes in DOM, i.e. hover changes element appearance of a
>> button.
>>
>> My diagnosis is a bit Chrome specific, but since we're getting similar
>> reports from FF users too, I'm worried that I'm missing something more
>> general.
>>
>>
>> --mikko
>>
>>
>> --
>> Mikko Mononen, Software Engineer
>> http://tinkercad.com - Solid modeling for artists & makers
>>
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--
Mikko Mononen, Software Engineer
http://tinkercad.com - Solid modeling for artists & makers

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