Prims vs Land Impacts

[Leaf Illusion]

My apologies if this is covered elsewhere, I did look... As I am starting to move some of my SL mesh creations onto Kitely I noticed that Kitely uses prim counts rather than Land Impacts like the mesh items in SL. Items that were multiple land impacts in SL seem to appear as a single prim when uploaded into Kitely.

For SL I often create larger items by using 2 smaller mesh parts which I link together after upload. Because each smaller part has less than 0.5 LI, when I link them in SL the land impact comes out as 1 land impact or 1 prim. I have found I actually get lower land impacts and nicer details that way. However if I do that in Kitely the two parts each are created as 1 prim and I get a 2 prim object when they are linked (even if they are set to convex hull.) Thus it seems I will need to rebuild them in Blender to create a single larger mesh item to use for Kitely (or live with the doubled prim count.) From what I have seen so far it is also possible to create a much larger single mesh in Kitely that will register as only 1 prim. So something that might be 5 land impacts in SL for example only counts as 1 prim in Kitely. This gives an obvious advantage to creating a larger mesh item, or combining multiple items in Blender to import as a single item, thus getting more items for less prims on my region. (Not sure I would actually do this, but in theory I could create some pretty impressive low prim builds...)

OK, my question is should we expect that Kitely / Opensim will at some point adopt the SL style Land Impact system? If so will mesh based items that currently show as 1 prim suddenly have a larger number of prims/ Land Impacts?

Since someone will likely mention it, I do understand that bundling numerous items into a single larger mesh item will create more server/viewer load, even if it only counts as 1 prim. So if an item is 15 land impacts in SL and only 1 prim in Kitely, it seems logical it will still create a similar server/viewer load in both. Regardless of number of prim or land impact counts a formula assigns to an object, each triangle face still takes processing power to render.

[Ozwell Wayfarer]

Hello Leaf,

Things work a little differently here. Basically, you are correct we measure things by how many physical parts an object has. So you benefit from joining objects together. So if you link two objects that would be 0.5 PE in SL, here it will be 2 PE. But if you arrange two (or indeed, 200+) of these components in-world, then export them out and join them in Blender, import it back in and its 1 PE.

1 Physical object is 1 PE regardless if it is 4 tris or 40,000. This is good as it gives you more breathing room as a creator, but also bad in that some will abuse this. It is up to the creator to ensure the content is efficient. I would not expect this to change anytime soon. Inworldz has a PE/LI system similar to SL but they are the only ones so far as I know, and Inworldz is Inworldz. I spoke to Ilan about it a while back and he said that Kitely certainly wont implement this as a feature unless Opensim in general does. I cant see any reason why anyone would do this.

Still, it makes sense to stick roughly to SL standards when designing. But if you can slim your design down by a few prims by joining things, that cant be a bad thing. I have often joined up pieces that share the same texture. But yes, if you want your builds to be as efficient as possible you will likely need to do some rebuilding.

Another crucial difference is upon upload, if you do not specify a physics model, the uploader will use your HIGHEST model as the physics shape. Ok for low poly stuff but generally, to be avoided. Physics is set to Prim by default, not convex hull. When you export your builds using firestorm, it guts the physics model. So in general, I tend to reduce the build into two linksets. "Simple stuff" like walls and "complex stuff" like windows and arches. That way I can import the basic stuff using the highest physics model and not re-upload for each component. Then add the more complex components individually, making sure the correct phys and LOD models are re-uploaded.

You are also limited to 8 texturable surfaces per mesh, as in SL.

EDIT - Just a thought too, though your builds may have effectively doubled in Land Impact, do remember that people have a lot more prims to play with in Opensim. The fact that something is just 1 PE/LI is not such a big selling point here.

Hope that helps you!

[Zuza Ritt]

Almost everything said by Oz... but...
When you cover whole region by high poly meshes, you will recognize it on lag. Try it at your home standalone, it hurts significantly:) Other users maybe cannot recognize it, or they do not know your object are the guilty one, but I believe good creators are not cheating with huge amount of vertices and sloppy work. The fact you are uploading stuff either into SL can help you on this way, to keep it as "small" as possible.
Physics could be a little bit tricky part, Blender got some unpredictable issues with root in uploaded object, but everything can be solved. A criterion for objects joining could be comfort for later retexturizing, especially if you consider to sell your creations. Nobody cares if object has 5 or 1 land impact, as long as it is beautiful and useful:)

[Ozwell Wayfarer]

Well...I did recommend keeping it roughly to SL standards but it probably is good to stress that point.

But there are exceptions. I always point out my trees. In SL, because size tends to add to LI/PE, things like trees are quite heavily penalized and so I have to sell different lower poly ones. There are many "top" creators selling sculpted prim trees that would be 100-200+ PE in the SL uploader if you tried to upload the same sculpts as mesh. Well above the 30-40 PE my trees weigh in at, but of course that is unacceptable in SL, and people would rather buy the 10-25 PE sculpted tree, even though it actually creates more lag. Because in SL, PE savings beat lag considerations 99% of the time (in the eyes of the customer).

That being said, Opensim takes it too far the other way, as there is no way my trees should be considered as 1PE really. I think 10-20 is a fair estimate. But of course, prim counts here mean a lot less, so its all relative. PE/LI is a bad system to begin with.

It all comes down to being sensible.

No grid has a real system for working out this stuff. Even SL ignores the texture load of an object, which more often than not is actually a more significant issue than geometry. Penny Patton has hammered this point to death *and rightly so* on her blog and at SLU. I have confirmed with Ilan in conversation that scripting and textures are more of an issue than actual objects in terms of server load.

You do have access to an FPS meter by accessing the advanced menu in your viewer and then selecting "Advanced-Performance Tools - Statistics Bar". Its worth keeping open while testing things, but obviously even this is relative to your PCs original performance levels.

[Zuza Ritt]

In hindsight, I hope it does not look like I am questioning Ozwell's comment. On the contrary, I agree... I have just put my two cents in.

[Leaf Illusion]

Thanks, that helps clarify. Sounds like it still all comes down to building as efficiently as possible, keeping textures small and polys to a minimum, so will continue with that on my quality products. But I can see a place for creating some less well-engineered products, it would be nice to not spend 2-3 weeks on a single simple item trying to squeeze every possible triangle out of it. I think I'm two weeks into OpenSim so still a lot to absorb. Basically a friend suggested I should put some of my creations on Kitely Market so I'm giving it a try.

Thanks again!

[Ozwell Wayfarer]

@Zuza - Aww, so you dont want to fight? Drat . lol I didnt take it as such Zuza our advice basically agrees. I am just too verbose for my own good and needed to add another two cents

@Leaf - Maybe I am nit-picking on semantics here, but I am not saying to put out "less well engineered" stuff. What I am saying is you can do more without restriction. So details that were represented by texture (stone/wood carving or ironwork for example) can actually be modeled with vertex instead. Weather you think it is "worth it" or not is your call as a designer.

its worth also remembering that in OS, not every server is equal. People running a region on a home PC will likely have a lot less computing power than someone with a Kitely region or running OS on a dedicated server. Its not like Sl where performance is broadly equal across the grid. So I think experimenting with selling "high poly" models is ok, so long as you clearly warn people beforehand in the listings. Land is so cheap here that I am sure people would give over a whole sims resources to a small area of high poly loveliness if it was available. Right now, OS is all land and little content.

But if you want to reach the most people good lower poly design is the way to go for sure.

So, all in all it boils down to more possibilities. Lots of potential to explore. Which I think is great!

If I can offer you any more help, just send me a message here or in-world. Best of luck bringing your creations over!

[Leaf Illusion]

@Ozwell - I guess my comment about less engineered items is aimed more at myself and my tendency to spend hours pulling triangles from models, then testing, then repeat. Often on an item not really worth all that effort. In creating mesh for SL I've aimed for a 1 Land Impact maximum, which means I've had to spend a lot of time on that "lowest LOD" model. As you probably know if you want to keep it under 1 LI in SL you have to have 12 or fewer triangles in that lowest LOD model (my own observation.) That results in some pretty terrible looking stuff when viewed from any distance, especially for those poor people on a old graphics card and using a really short draw distance. One way I've found to improve appearance in those situations is to cut my smaller mesh items into halves, allowing each half to then have 12 triangles at the lowest level. I then import to SL and link them. If I am careful with the high level triangles I can get something that looks pretty decent from any distance. But when I tried that in OS I got that surprise on the prim count (I don't think it is called prim in OS, don't have the terminology down yet, sorry.) But rest assured I will not stop putting out well engineered stuff. I tend to be a bit too anal not too...

[Ozwell Wayfarer]

Fair enough, I know how that goes. I have a million things in the works that just need a little more work.....just a little .

For that final LOD stage, if the item your building is fairly big, you can loose that LOD stage altogether. I do this often with houses and large componenets and nobody has ever complained about it either here or in SL. Obviosly I am only referring to large things here, as LOD is relative to scale. If your unsure, then provide two models, one with "Low LOD" and one with "high LOD". Just explain clearly in the listing. There are so many variables these days that I think the best approach is just to give people options and clearly explain what those options mean.

....and (maybe a bit elitist of me) by personal opinion is if you try to log into a complex 3D world using something with less computational power than my kitchen toaster.....well, you deserve what you get. I dont design for people who still power their PCs with hamsters. If people want beautiful graphics, buy a computer that can render beautiful graphics. Decent PCs and Laptops are pretty cheap nowadays. My PC that I do all my design work came in at less than 500EUR/400GBP/800USD and I can run 3 viewers, blender, gimp and paint.net, and browse the internet in parallel without any performance issues. The consumer has to meet the designer halfway here.

Baked texturing always made me chuckle for this reason. Baked shadows became so popular in SL because people didn't have the power to run SL with native shadows turned on. So one seamless textures becomes a dozen, all with different shadows baked onto it at different angles. Then people wonder why everything takes so long to load, not realizing they just amped up their texture load to obscene levels.This is why I tend to use seamless + materials these days and only bake when nothing else will do.

This is often where the diversity of people and places in virtual worlds becomes a problem for us designers. Some people want ultra-real and have the hardware to back it up, others want performance and dont care so much for the graphical side of it (a la minecraft), and others who fall in between.