The Secrets of Mesh Landimpact

LiIconI’m hearing more and more SL creators saying that the Landimpact calculation is borked and that LL should change it. I don’t agree with this at all, i believe Linden Lab have done a very good job with mesh and its resource calculations and I’m a better 3D modeller because of this.

Before i try and explain the secrets to getting your mesh creations low in land impact we need to first understand why the calculations are the way they are.

It is my belief that Linden Lab took a much more strict approach to how mesh costs as a way to keep more accurate calculations on the resources an object uses. If your mesh object costs 500 land impact, thats not because LL are being nasty to you, its because your object costs the viewer a high amount of resources to download and display. When you complain to the Lab to change the land impact calculations you are basically requesting that you be allowed to create inefficiently and bork the grid with your monstrosities taking the grid performance backwards.

I fully believe the mesh Land Impact calculations are fair and important to teaching us how to make very efficient 3D models which will help SL become more stable as long as we stick to calculation LL have set.

Mesh is extremely flexible and SL’s import options give us a lot of control on aspects i expect some of you never knew about. I don’t blame you for not knowing, there is nothing written down to explain the secrets of uploading low cost mesh, so bare with me and i’ll try and share what i know so far.


What Makes a Mesh Object High Landimpact?

There are FOUR factors that can cause a mesh object to be high in land impact.

In Blender: Left a low detailed Bottle – right a higher detailed smoother bottle

(1) Detail: The amount of vertices used to create the object. The more detail, the more points need to be calculated.

(2) Size: The size of the object in world. Generally believed the larger the object the more resources it can eat up, but this might actually be related more to LOD than object size as you will find out if you keep reading.

(3) Physics shape. This defines the shape of the object that you walk on or bump into. The more detailed this is the more resources it takes up, the higher the Landimpact.

(4) LOD: or Level of detail. If you still don’t know what this is, go read my blog post about it because its VITAL to reducing land impact costs.

These four factors when maxed out will give you a mesh object HUGE in land impact. But we are given the options to modify these factors when importing and it’s here that we get to reduce the land impact cost.


Example One: Default Uploads

In this example i shall compare a low detail bottle with a higher detailed bottle on default import SL settings.

Low Detail Bottle.


This low detail bottle is being uploaded on SL’s default LOD import settings and with Physics shape set to HIGH. It has a calculated landimpact (li) of  7.7 which might get rounded up to 8Li


Inworld the Bottle is rather big and as predicted the bottle’s land impact has been rounded up to 8Li.

High Detail Bottle.


This Higher detail bottle is also being uploaded on SL’s default LOD import settings and with Physics shape set to HIGH. It has a calculated landimpact (li) of  a whopping 35.2 . This shows how much an object can change when adding more detail.


Inworld the Bottle looks noticeably smoother than the previous one but at 35 landimpact i can hear you with arms up in the air saying “But at the cost of 27 precious land impact WTF!”.

What if i said you could reduce that 35 landimpact and still retain that size and extra detail? What if i said you could reduce it to 1 landimpact and still retain the size and detail, would you believe me?

Who needs Physics anyways?

One trick i use is virtually removing the Physics shape. Some modellers make their own physics shapes as a separate model thats combined during upload. Many simply use SL’s built in physics shape generator which builds a physics shape from the model you are importing. What i have found is by making the physics shape as small as possible this can reduce the overall landimpact dramatically. And the simplest way to do this is by adjusting the ‘lowest Level of Detail’ setting in the import options and using that as the bases for our bottles Physics shape.

Example Two: Reducing Physics shape


The lowest ‘Level Of Detail’ is the often the last version of an object you see as you walk away from it. For large objects your draw distance is low enough that you wont see this LOD stage so i find that it’s ok to reduce it to ZERO.


Now i switch to the Physics TAB and choose ‘Lowest’ from the ‘Step 1:Level of detail’ section drop down menu. This is selecting our objects Lowest LOD setting as the bases to create its Physics shape.

I CLICK  the ‘ANALYSE’ button then ‘Calculate’. You will see that my Bottle has a predicted Li of just 7.3Li. 


Thats a drop of about 27 landimpact just by changing the Physics shape. But i can understand if you are reluctant to import objects that are walk through and have no mass. I will come to that later in this blog post.

The LOD Effect.

This is a subject that i struggle to explain to people. Some people get it , others don’t and im really sorry if my own explanation of LOD does not help you understand. The size of an object effects how LOD chooses to display your object and understanding how it does this will lead you to consider how best to import your model. So here goes, wish me luck…

Example Three: The LOD Rings.

If you still haven’t read my Blog post about LOD ,WHY NOT? – To quickly surmise, every object has four rings around it. The further away the ring the lower in Level Of Detail (LOD). As you walk up to an object you are walking through these rings, so as you approach you first enter the outer ring of the Lowest LOD causing the object to show its Lowest Level Of Detail. As you get closer you walk through the Low LOD ring, and then Medium before reaching the high LOD ring and see the highest detail of the object.

Ring distance is for visual purpose and does not accurately portrait the distance between each LOD ring at this objects size. In fact i feel the rings on this giant bottle would be at least 3 times bigger in distance from the object

With my giant bottle we can see that the LOD rings are HUGE!. I’d have to walk quite far away just to be at the distance to view the ‘Low’ LOD.


What many don’t realise is that the LOD rings are tied to the size of the object so when i shrink the bottle down, the LOD rings shrink too. Suddenly I’m at the distance to view ‘Low’ LOD. This is why some small objects disappear when you stand 1 metre away from them. But the SL Mesh Import has options to counter this, and its this effect that will allow me to reduce the giant bottle’s Li down even further.

Example Four: Doing away with the LOD

As demonstrated above the the giant bottle’s LOD rings are so huge that you would have to be really far away before it changed to a lower LOD. Because of this i can actually do away with some if not all the lower LOD shapes during the import process.


Here you can see I’ve reduced the LOD settings for ‘Medium’, ‘Low’ and ‘Lowest’ to ZERO, practically removing the ability for the object to display the model at these Levels of Detail.


Combined with the fact we also set the Physics shape to the none existent ‘Lowest’ LOD, when i finally click calculate i get a predicted Land Impact of 1.7 Li


And once imported I’m delighted to see that the high detailed large bottle has been rounded down to only 1 Li.  – MAGIC! –

But if you are anything like me you probably dont want people walking through it and since we removed the Physics shape there is now nothing to stop that happening. Well I’ve discovered that our faithful old Primitive cube is still a very handy useful tool for creating very simple Physics shapes that will not add much if anything at all to the Mesh Objects Landimpact due to Prim Absorption.

Example Five: Using the PRIM for Physics


Im using one simple PRIM cube to create a block that will stop you walking through the bottle, thats all i need it to do really. I Link the Bottle to the Prim making the PRIM the root.


Notice that the landimpact is still only 1Li. Now all i do is set the surface of the PRIM to 100 Transparency. leaving me with a bottle i cant walk through.

Small things need LOD boost.

So far ive concentrated on showing how to make  low landimpact HUGE objects but there is a flip side to this. I mentioned briefly during my explanation of LOD rings that some objects disappear quickly from view due to their small size. Whats happening is that because the mesh objects are small, so are their LOD rings and step out of their range quicker than if they were big. But this can be countered by doing the opposite to what i did to reduce the Bottles large land impact.


So my giant 1 Prim Bottle is shrunk right down in size by my feet (yes i know i need to wash). Look what happens when i move away from the bottle, it becomes a single white line. This is because i reduced the ‘Medium’, ‘Low’ and ‘lowest’ LOD settings during upload because i knew the object was going to be big.

This shows that i cant use the same import settings for an object thats going to be big with an object thats going to be small. You have to consider the size and use of your object so you can optimise accordingly during import.

Example Six: Boosting LOD


What i now need to do is import my Bottle again but this time with the idea of having it stay visible and more detailed for longer while small. So instead of reducing the LOD settings i have to increase them which will add to the land impact but hopefully be countered by the fact the bottle will be small.

NOTE: when it comes to mesh simply making it smaller does not necessarily mean the Land impact will reduce because you will find you have to boost the detail of the LOD so that its seen at a good distance.


To get a better idea when calculating the costs, you can change the scale setting in the upload options. My calculated cost is 6.8 which is a bit more than 1li that the large bottle had.



So the small bottle was rounded up to 7 Li but can be seen at a much greater distance. This i hope shows that you should consider where you mesh object is going to be. If this small bottle is going to be on shelf in a small room, then i should probably have not set the ‘lowest’ LOD settings so high reducing the Li. But for being viewed outside this small bottle needs to be this high in order to be seen so far away.


And Relax.

Well i hope this all didn’t just go over your heads. It’s actually really hard to explain it all but once you get the feel for how sizes, distance and detail effect The Mesh you’ll be making awesome efficient mesh objects in no time. Plus once you figure it out and master, you’ll soon appreciate how Linden lab have incorporated mesh. It forces you to be good, it forces you to learn to be efficient so that your creations can download and be moved about by the crappest of computers and slowest of internet connections.

Sorry if this post did nothing but confuse the hell out of you 🙂

ALSO, if you are interested in learning how to make a mesh object but have never touched a 3D programme before then my 6 part PDF tutorial ‘MAKING A MESH’ is still available inworld at Nemo Beach. LINK

26 thoughts on “The Secrets of Mesh Landimpact

  1. Hi Loki, great tutorial! You should also tell people that they can find a whole mesh tutorial made by you on the Escapades sim.

  2. Greetings Loki.

    Thanks for your awesome tutorial.

    I strongly believe that if the community (specially content creators) where more aware of SL limits, and more concerned about the lag created by their stuff, than blaming it all to LL, SL would become a better environment for all us. If they were a bit more aware they would be more responsible of what they create and sell.
    That’s why i believe the contributions like yours are excellent resources to educate those willing to make SL usable.

    [I]Plus once you figure it out and master, you’ll soon appreciate how Linden lab have incorporated mesh. It forces you to be good, it [B]forces[/B] you to learn to be efficient so that your creations can download and be moved about by the crappest of computers and slowest of internet connections.[/I]

    While i agree when saying LL’s way to implements mesh cost makes sense in some aspects, and encourages you to make efficient content (once you figure out what makes your model cost high LI), i don’t it forces you to do so.. not at all, specially if you uploading non static models (attachments or rigged meshes). I believe the upload system is so flawed when referring to the upload cost (L$). On my opinion the ratio that control upload cost should be much more picky. At least as much as the ratio that control LoD and physics performance cost. Although it’s not cheap (in LI terms) to upload an inefficient model, it’s extremely cheap (in L$ terms) to upload it.

    Also i think the 64k vertices limit per face/loD is extremely permissive.. just consider you can (theoretically) upload a costume with up to 64 linked meshes with up 64k vertices per face/LoD… at relativity low prize.. ‘/me shivers’.. What is not any theory at all, is a fact, is that there are avatars and stuff with ridiculous amount of polys for a platform like SL. SL is not a render engine, it’s a buggy living platform were everything should be streamed and rendered in real time by users using most of them old machines and bad connections, not designers using expensive machines built for that, nor gamers. Those models have not sense on here.

    What disturb me most is that this is not something new.. we have been suffering the abuse of sculpties for years.

    • There are some stuff you mentioned that i dont really know about since i only really got into 3D modelling just as Mesh was being introduced into SL, so i cant comment on the 64k vertices thingy. I also had not considered the Linden Dollar cost of importing and how that is calculated.

      What i can comment on and agree with is that there are a lot of people who are saying ‘I want Sl to look like PS4’. They want PS4 graphics content that streams in real time from a web server on a 2mb connection to a £200 computer, is there any game currently that can do that?. You would have to be EXTREMELY smart and efficient with your modelling.

      • About the 64k vertices limit (on sl):

        Models made in games are actually far far more efficient and low poly that the average built for SL. On one hand, of course, this is why we are talking about professional vs amateur content creators. On the other hand there is no necessity of high poly models in modern games, where you can make the scenes and models efficient and very realistic (assuming you have the proper software compatible with that technology) thanks to normal maps, specular maps, shaders, realistic particles… most of those features are not available on SL platform.

        My point is that the fact that you lack of tools to make something looks as good as a ps4 game doesn’t mean you should supply it by doing your stuff extremely high poly.. the price to pay is too high. Costumers and creators need to know that. Sometimes we use on a daily basis objects, clothes, garments, avatars etc… made from more polys that display models used to make tv advertisements, even 3d movies and of course games, witch is insane.

        I must clarify that i am not talking about your creations, Loki. I think they should be put as example of efficient stuff for SL 🙂

  3. Very nicely done and well illustrated, Loki. These are new concepts to most of SL’s amateur creators, but they needn’t be difficult to grasp. I’ll admit that I found the business of Land Impact off-putting at first myself. Once I learned the basics, as you have shown, they made my modeling much more efficient. I’ll bookmark this blog post and share it as I talk with other creators. Great resource!

  4. omg. i just found this write up of yours. wish i had seen this a year ago. i work in sketchup and love it. was so easy for me to learn. but couldnt figure out why so many of my builds were high Land Impact compared to stuff i’ve seen in world. this explained so much. i started going through my mesh files and running them back through the Mesh uploader and adjusting thier LOD’s at the different levels. soo much better now thanks to you.

  5. Let’s face it, lindenlabs calculation on mesh is insane, creators can’t make any objects with detail and rounded
    parts on a object is a nogo.If people are happy with low LOD objects and a lot of things inworld show up as triangle
    and are only visible when your nose bumps against it, well, fine, but for me the whole mesh thing is a farce.
    Go comparing a house build out of normal prims and one made out of mesh, the normal prim house is rock solid, the mesh house is a low lod disaster. Well, thank you lindenlab, and eh…sculpties forever !!!, yep, they are difficult
    , takes a lot of time and energy to make good looking objects, but….it’s by far much, much better dan any mesh,
    Lindenlab ruined Secondlife once again, it’s dieing, and we all know it, well done Lindenlab !!

  6. Yeah, i understand why you disagree, and why Lindenlab ignores all, for LL the landbusiness is their core bussines, for you mainly the clothing business. And clothings or other attachments do not suffer from the insane
    landimpact calculation. That is…as long as you don’t rezz them on the ground, but i think nobody wants to do that
    with super mega high poly dresses skirts, pants , whatever type of clothing, because if you would drop a dress or
    jacket on your land , then around you it would suddenly become terrible empty at your region, and it would fill up your lost and found folder, returning houses objects etc.
    In clothing shops you won’t see any mesh clothing, the only thing you see are boards at the wall, no wonder, if
    a creator would display 10 dresses the 15,000 prims region would run out of prims.
    So, in other words, object creators have to suffer because 100 faces and below counts as 1 prim, and clothing creators can do whatever they want because there is no limit for them.
    This leads to enormous lagg all over the grid, and i feel sorry for the newbies out there and for people on slow
    networks , as they can’t even see properly dressed people, clothing simply doesn’t show up for them.
    And mesh bodies seem to be not visible for them either, all they can do is enjoying some ‘ triangles’ out there,
    objects with low lods, cars that look like they’ve been involved in accidents, but coming closer suddenly those cars seems to be fixed, well, the wheels are still a bit square, but who cares, after all, it’s better then minecraft….still.
    But well, doesn’t matter, any sculpty is stil 2048 triangles tp play with, and so Secondlife will be a mix of normal
    prims, many sculpties, and perhaps a few mesh objects here and there for as long as the grid is alive…..until it dies

  7. Someone posted this link inworld in a group chat and I am so glad they did! You explain it so well. I’ve worked in Blender for many years, but am just starting to get into mesh for SL. This is the only place so far that really explains the uploading of mesh and how to adjust the settings. Thank you!!!!

  8. Hi Thanks for this explanation it is very helpful indeed and simple i can not believe it…. THANKS for your efforts.

  9. This is untrue and easy to prove, make something in SL out of prims, export then re-import the exact same file, the land impact will double some times triple. Everything should be the same, the prims should have the same number of Triangles and Vertices as the mesh version, as the mesh was 100% based on SL’s prims that got exported. I would love to hear the explanation of this. Mind you I didn’t mod the file in any way, just exported, imported the same file.

    • I would assume it is because prims do not use the same calculating for land impact as mesh. Remember you have instances where simply adding a normal map to a prim surface or cutting a wedge in the prim or linking and resizing a prim will suddenly give it HUGE land impact change. I believe that is because the Prim calculation is not accurate to performance. I think back in the early days they decided all prims should be worth the same count even if rendering a sphere costs more performance than a cube. It was done to make it easier for users.

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