[webkit-dev] WebGL performance

[Simon Fraser]

On Oct 22, 2009, at 12:38 PM, Oliver Hunt wrote:

> On Oct 20, 2009, at 5:58 AM, Boris Stock wrote:
>
>> I have an question regarding the WebGL implementation. It already  
>> seems to be very fast. Of course a lot of stuff is important like  
>> in "native" GL programs (rendering triangle stripes vs. X and  
>> stuff). But how far do you think will a future stable release of  
>> WebGL match a "native" GL implementation in performance? Is  
>> JavaScript speed a big show stopper there? or because the GL  
>> surface is not fullscreen and can be overlayed with other layers  
>> (which is also a big peformance impact on any system which overlays  
>> something over the opengl surface / view).
>
> At the moment there are not any significant webgl based apps (due to  
> the current state of the spec) so we don't yet know what issues will  
> be performance problems.  On the topic of overlay performance, there  
> is the requirement that a canvas element (WebGL or simple 2D) must  
> composite correctly, which effectively requires a call to  
> glReadPixels if the renderer is not able to composite on a hardware  
> directly.

Note that WebCore does have support for accelerated composting of web  
content (see the ACCELERATED_COMPOSITING code paths), and WebGL makes  
use of this, so there is very little performance impact of layering  
content on top of a 3d canvas for platforms that have an  
ACCELERATED_COMPOSITING implementation.

Simon

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