[sldev] Avatar Rending Speed

Dave Parks davep at lindenlab.com
Fri Jan 18 17:05:10 PST 2008


My numbers could be a bit off here, but one avatar in SL has as many 
triangles as an enemy soldier in half-life 2 BEFORE attachments (about 
8-10k triangles).  Attachments can easily add up to over 100k triangles 
at higher LOD's for a single avatar.  Also, enemies in games all tend to 
have the same material properties, so they can be rendered very quickly 
in batches together, whereas every character in SL is unique, and most 
attachments are unique as well, having their own distinct sets of 
textures, animated texture coordinates, and surface properties 
(transparent, fullbright, shiny, and now glow).  A lot of this has to do 
with prims.  Prims are network light, triangle heavy.  I've seen some 
really awesome looking sculptie avatars that run great.

Besides all that, though, it sounds like SL is tickling your GL drivers 
in a bad way.  A few avatars, even with heavy attachments, shouldn't 
hurt framerate that badly.  What's your exact system spec (please 
include OS version and driver version and viewer version)?


Callum Lerwick wrote:
> On Fri, 2008-01-18 at 07:46 -0800, Dzonatas wrote:
>   
>> Callum Lerwick wrote:
>>     
>>> You're barking up the wrong tree. If you want higher framerates, figure
>>> out why avatar rendering is so goddamn slow. It dwarfs all other
>>> rendering by far.
>>>   
>>>       
>
>   
>> There was some patches posted to speed up avatar rendering, but that 
>> effort has been ..uhm.. derailed.
>>     
>
> Where?
>
>   
>> Now that Windlight is coming out with its low quality avi tradeoff for 
>> framerates, those patches don't seem to matter anymore.
>>     
>
> Wrong. On even my fastest systems, (Radeon r300's) a mere three avatars
> on screen drops the framerate like a rock. Impostors may help in really,
> really busy areas, but they are not the answer. Impostors also eat up
> valuable texture space.
>
> Something seems very very wrong in that hanging out with a mere two or
> three friends in a mostly empty sandbox kills the framerate so much.
>
> I've stood in busy areas and toggled Avatar Vertex programs on and off.
> At best, there was maybe a 0.1 change in framerate. Vertex programs do
> not appear to be the answer either.
>
> All profiling I've done consistently shows that the vast majority of run
> time is actually spent inside the OpenGL drivers (and OpenJPEG). This
> suggests to me that the problem is not a cycle-shaving issue in
> slviewer, but a fundamental issue in the avatar rendering algorithm, an
> issue in the way OpenGL is being used.
>
> Game engines like Doom3 and Source appear to manage to render larger
> numbers of much more detailed skeletal animated entities, with much
> higher performance on the very same hardware. As they're not currently
> open source, I haven't a clue how they're doing it.
>
> And of course SL seems to be locking up my Wintendo upon loading the
> HTML login screen at the moment, so I can't try and get some real
> numbers at the moment. Sigh.
>   
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