Dear Kay,
You might wish read how Avatar Draw Weight is calculated:
http://wiki.secondlife.com/wiki/Mesh/Rendering_weight
Base calculation is indeed linked to the number of triangles an avatar has,
and, of course, any attachment will add to
that value. But extra settings like glow, flexi, and some scripts will add even
more.
But remember: except for scripts on attachments, Avatar Draw Weight is a
measure of /viewer-side /lag, i.e. how big an
effort /your/ graphics card has to make in order to render an avatar, and /not/
an impact on the /server/ where OpenSim
is running. While an avatar with tons of attachments needs to download them
first — which will create some impact on the
simulator, as it starts sending all that data to you; the more avatars with
attachments on the region, the more effort
the simulator has to do — after they're fully loaded, they should have no
impact on the simulator any more (attachments
are phantom). Scripts, of course, running server-side, are a different story.
Scriptless attachments should not make a
huge difference on the simulator (except during the initial load).
On the other hand, viewers will definitely notice the impact of high draw
weights. This is mostly noticeable on low-end,
old graphics cards, which cannot process so many triangles per frame. It's not
so easy to find specs for each and every
card out there, and to know where the threshold is. Modern, high-end graphics
cards can render so many polygons per
frame that I would seriously suspect that they would not notice much of a
difference.
A simple rule of thumb: Draw weight of 1000 = just the standard avatar = 7500
triangles
Everything above 1000, divided by 5, gives the amount of extra triangles
(assuming no glow, no flexiprims, etc.) So an
avatar with draw weight of 25,950 would have at most 12,500 or so triangles. 18
of those would come up to 225,000
triangles. As far back as 2001, high-end graphic cards would easily handle
60-100k triangles per frame, assuming 30 FPS
(http://www.gamedev.net/topic/55764-how-many-triangles-do-most-computer-games-render-per-frame/).
In 2004, 400-500k
triangles at 30 FPS seemed to be more typical
(http://www.gamedev.net/topic/253770-how-many-triangles-can-your-engine-handle/)
Raz Welles has a thorough explanation of where all those triangles come from:
http://razwelles.blogspot.pt/2012/06/opensim-and-mesh-understanding.html He quotes a
"typical" graphics card being able
to render 1.5 million triangles at 33 FPS. His articles is from June 2012, so
you can see how the amount of triangle
rendering per second has been growing steadily in the past decade.
Still, all these numbers are merely a rough guideline. LL's own engine on the
viewer might have performance limits as
well — i.e. it may not be able to send all those triangles to the OpenGL layer
quickly enough for the GPU to tender
them. OpenGL, in return, also has a limit on how many triangles it can send.
And finally, these counts are usually for
untextured triangles — add texturing, and the number obviously drops!
However, I think it's a relatively safe bet that anyone with a graphics card of
around 2010 or so should easily view
those 18 avatars with Avatar Draw Weight of 25,950, as easily as if they had no
attachments, and still get 30 FPS, if
they don't turn on shadows or the more sophisticated advanced lighting options
on the newest viewers.
I hope this helps.
Cheers,
- Gwyn
On 29/08/2012, at 16:18, Kay McLennan wrote:
OpenSim-User List Serve Colleagues,
I currently use the Zen and Phoenix viewers (3) and noticed how the "avatar draw
weight" feature in these viewers
reveals a dramatic increase in my draw weight whenever I add any attachments to
my avatar (read: prim hair, face
light, sculpt shoes or clothes, etc.). More specifically, without any
attachments, my avatar has a draw weight of
1,000 but with the above listed attachments has a draw weight of 25,950.
Further, when I was at an [OpenSim] in-world
meeting last week, I observed how many of the approximately 18 avatars in
attendance had even higher draw weights.
What is the significance of the avatar draw weight when it comes to region
performance and lag? More specifically, if
a region can support 18 avatars with fairly high draw weights, could the region
support double the number of avatars
if everyone used an avatar than only had a draw weight of 1,000?
Thank you in advance.
-- Kay McLennan
--
"I'm not building a game. I'm building a new country."
-- Philip "Linden" Rosedale, interview to Wired, 2004-05-08
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