What is "Agent Time"

[Monica Balut]

I know that this is not specifically a scripting question, but I view this as the forum with the most knowledgeable people about the geekier side of SL.

I've been trying to pay more attention lately to various parts of the Time secion in the Statistics Bar.  I've read the wiki about it at http://wiki.secondlife.com/wiki/Viewerhelp:Statistics as well as a few other sites that come up in a Google search.  Most of the lines are self explanatory but I'm left with one that eludes me,  Agent time.

The wiki defines that as: Agent Time - The amount of time spent updating and transmitting object data to the agents.

 

What is this "object data" that is being transmitted?  I can find no detailed explanation of what exactly that is.

[Geldsbard Freck]

First of all - you, when in SL are the "agent" - more accurately, it's your computer.

Everything you see (except particles) in Sl is an object, even the sky (known as a "sky box" - this may not actually be the case with SL but is normally true in most 3d virtual enviroments. DirectX has a function to display a "background" texture but it behaves differently than the SL sky so it's difficult to tell).

What you see on your display is rendered by your computer - not SL; SL merely sends data to your computer.

Object data is the data your computer needs to display an object as intended - it's shape, scale, rotation, translation, texture or phong shading , object features, etc. This is the object data DirectX or OpenGL on your system needs for every object that exists within your view to be able to display them for you. Animated objects have this data updated periodically even more so than static objects.

 
The amount of time the server spends to update this data to your system is the calculated "agent time"

[Monica Balut]

Thanks.  Best explanation I've seen so far.  Does ALL that data get sent to each av during each slice?  Or, does it just send updates?  The reason I ask is that I often see a spike in agent time as new avatars arrive on the sim.

 

One more, possibly related, question ... I thought that image time was the time required to send texture info up to the viewer, but you mention textures as part of agent time.  So how is image time different from that?

[Qie Niangao]

Lots of things happen when a new agent arrives on a sim, but yeah: at that point, their viewers need to get sent all the object data in view (and some that's not in view), and they'll keep getting updates about changes to the set of objects that populate their "interest list." You might find it instructive to turn on "Develop / Show Info / Show Updates to Objects" for a while to watch what sort of stuff the sim sends to your viewer about objects (and avatars).

Most raw texture data, as I understand it, loads from a central database, not the sim, although the sim tells the viewer which textures it needs to load. I'm not sure if that bit of sim processing is accounted for in Image Time or Agent Time. There is, however, an exception: the local sim gets the (temporary) texture data created when an avatar bakes appearance in that sim, and has to transmit that data to any viewer that rezzes the avatar, but I don't know how that processing time is apportioned between Agent and Image times. (Incidentally, avatar baking is about to change under Project Shining, moving the baking process to a centralized service.)

[Monica Balut]

Qie,  I did as you suggested and looked at Show Updates to Objects.  There is a flurry of activity when the avatar just arrives to a sim and then it settles down, suggesting that only updates are sent after that.  That would make sense.

 

In spite of Geldsbard's and your excellent expanations, I'm still a bit confuse about the diffefference between agent time and image time.  If textures are loaded from a central database and not via the sim, what then is image time.  I had thought that image time was the texture download time.