Sculpt versus Mesh

[agentronin]

When I teleported into the Amazon River landing area I got this message in local chat:

Quote

 

Check yourself, do YOU cause lag?
1, press CTRL ALT Q to toggle in your viewer menu 'Developer' on
2. select 'Developer - Render Metadata - Sculpt'

If you are covered in white numbers, your items are outdated sculpt. change them. you are lagging yourself and everyone around you down

 

I did this and did find myself covered in those white numbers.

So what is it about sculpts that heavily burden the server? What is it about mesh alternatives that burden server less?

[Qie Niangao]

Not the server. It has to do with the efficiency of specifying the shape to be rendered in the viewer. Sculpts tend to be tremendously inefficient about that, so they contain a lot of useless complexity making them slower to render than comparable-looking Mesh items. So a venue may want to minimize sculpts to improve the experience of visitors -- make the place feel less laggy.

There are other differences, not all of them favoring Mesh, some of which are less important than they were before the day of CDN, but generally of interest to only the tech-obsessed.

[LittleMe Jewell]

Also note, like many things in SL that have to do with lag and avatar complexity/rendering, it isn't an absolute.  Not ALL sculpts are worse than mesh - just most.  And it is entirely possibly that other things an avatar has attached could be causing much worse lag issues that a few sculpt items.

Review the items you have attached that are sculpt and you can use the MP to start researching mesh alternatives to see if they are truly better.

[agentronin]

So the effects of sculpts will depend a lot on the amount of GPU power those who view me have?

[Qie Niangao]

Yeah, GPU, but also memory capacity, download bandwidth... potentially CPU. At popular venues such as the Amazon, the problem is compounded by the number of avatars in a scene and the amount of motion and other object updates. Throwing a few extra sculpts on each avatar can get to be a big thing.

Practically, if nobody wore a mesh avatar (nor head), it would be fine to have a few sculpties instead with no relative performance hit. But no venue is going to forbid mesh avatars.

(I should perhaps clarify from my earlier post: there are ways that sculpties can be used that adds some server load, too -- and other ways Mesh can do so as well. Those are uncommon and unlikely to be what venues are trying to avoid.)

[agentronin]

What is CDN?

[Qie Niangao]

CDN is "Content Delivery Network". Akamai may be a familiar name in this sector. It's a way of migrating copies of content (in SL's case, assets like textures, sounds, mesh models, etc.) to nodes close to the network's edge where end-users can get to them efficiently. 

[ChinRey]

7 hours ago, agentronin said:

So what is it about sculpts that heavily burden the server? What is it about mesh alternatives that burden server less?

As Qie already said, sculpts tend to be lighter on the server than mesh, not heavier, and a sculpt sues less bandwidht than even the simplest mesh.

The GPU load a single sculpt causes is trivial compared to any piece of fitted mesh you may wear but usually you need quite a few sculpts to make complex wearables (such as sculpt hairs) and they add up.

Sculpts also need to be converted to mesh by the viewer before they can be renderd at all and the code that does the conversion is a rather crude and inefficient hack. It's especially bad if the sculpt uses an oversamples map and unfortunately three of the most common sculpt generating tools (Prim Generator, Tatara and the Wings3D sculpt plugin) all create oversampled maps.