How to Upload Mesh with Low Land Impact

[AdamZadig]

Hi guys, 

I know this has been covered in other threads but most are over 2 years old and I wanted to see if there have been any recent developments as I'm only uploading mesh since yesterday. 

I'm trying to figure out how to upload with LOW land impact. 

I have created my own .dae and .blend files so if anyone would like me to send them the files I will be more than happy to do so if you want to give a real hands on answer. 

 

- So what can we newbies do to keep land impact to a minimum when uploading?

- What tips do you have for using BLENDER to keep objects optimal for Second Life? 

My case specifically, is that I am building my own DJ Equipment so it is very small. But my CDJ 2000 (CD Player) is 16 prims and I have seen even better looking ones only 1 prim! 

One point I would like to make is that although I built it all in one go on blender I have given it approx 14 texture faces. And it uploads as 3 seperate parts instead of one even though I have it as one in Blender. 

 

Thanks for any help and if anyone is willing to receive the files and check them out for yourself please message me in-world and I will supply a download link or something similar. 

 

AdamZadig

[Rolig Loon]

Well, for a start, you are only allowed to create a maximum of 8 materials on a single mesh object for SL, so 14 is a bit over the top.  That will explain why it gets uploaded in chunks.

The basics of how to minimize L.I. are covered very nicely in this article.  It's a little dated now, but nothing has changed since it was written.  You'll find that paying attention to making the simplest physics model possible will make a lot of difference.  Also, make your own LOD models and keep the geometry as simple as you can.  Land impact is a common topic in this forum, so you should be able to find a lot of current threads by searching here.

[Chic Aeon]

Nothing has changed except that the uploader will now split a mesh with more than eight faces into parts. Before it would just not upload some parts (this is as I remember from one occassion - I typically haven't used many materials until I switched to Cycles render).

 

Since you stated that your object is one piece in Blender, then you need to limit your materials to 8 or less OR purposefully divide the mesh into two parts and upload accordingly. 

IF you can, use the same materials on more pieces. You can put several textures on ONE texture within you graphics program (like a checkerboard) in accordance to the size and shape that they need to be for the parts the coorispond to.  Then you can have one material with various texture LOOKS. These of course will be changed together so if you are using specular or normal maps (or tinting or shine etc) think about which ones can go together in a combined texture.

If your item is indeed smallish, you should be able to get it down to one land impact.  Make sure that the lowest LOD is very very low. Use a cube for your physics model maybe .

 

Here is a good link on LODs from this forum long ago.

 

https://community.secondlife.com/t5/Mesh/Simple-mesh-pillow-13-prims/td-p/2482869/page/2

 

 Edit: Probably the most important thing in general that I forgot to say as it seems so obvious is that SL requires LOW POLY modeling in order to get low land impact. So stay away from the sub surf modifier and similar modifiers as much as possible and get rid of any extra edge loops that you can after applying the modifiers.  Don't follow tutorials that are meant for those needing RENDERS and not game objects. They will just get you into trouble *wink* unless you know what NOT to follow.

 

 

 

[ChinRey]

Welcome to the world of Second Life mesh, Adam.

 

Yes, building with mesh is a lot more complicated than building with prims or sculpts and if you want to do it really well, you need to understand a bit of theory.

The first thing you need to know is that land impact is absed on three "weights", estimates how much load and lag the objects causes at different steps in the trasnfer from the asset server to our computers. It's the highest of these three weights that matters so to reduce the land impact, you first need to determine which of them that is and how to deal with it:

The server weight: is the work the server has to do looking up stuff in the database. A linkset's server weight is 0.5 for each part plus 0.25 for each active script. To reduce it you have to merge several smaller meshes into fewer bigger ones. Unfortunately that usually icnreases the donwload weight so balancing the weights in a linkset is very important if you want to optimize it for max. efficiency.

The physics weight is the work the sim server has to do to handle the object. This is all about the phsyics shape (since evrything else the sim server does with the item is minor by comparasion) so to reduce it, you need to simplify the physics shape. One really nice trick ehre is to create two dae files, one with a single triangle, and one with jsut a simple cube. Keep those two files and use the single triangle one as the phsyics model for all items that don't need any physics at all and the cube for all items that only need simple box physics.

The download weight is the amount of data that has to be transferred and usually the largest of the three. It is based on the amount of (compressed) data for each LOD model weighed against an estmiate how often each model will be needed. This estimate depends on the item's size and that is why mesh can change LI when you resize it. There are numerous ways to control the download weight. Here are a few of them:

1. Make all LOD models manually!!! That is rule no. 1. The uplaoder does have a function to generate LOD models automatically but jsut like the auto-splitting function Rolig and Chic warned you about, it's horribly bad at it. Even the most inexpereienced mesh maker can do far better LOD models than the uploader can manage. The only thing the autogenerated models can be good for, is if you want to "zero out" one or more LOD models. That is, you decide you don't need that particular LOD level at all, so you jsut set the value to 0 to minimize its LI. You don't want tyo do that with DJ equipment though.
2. Give each LOD model the details it needs, nothing more and nothing less. The more vertices and polys a models has, the higher its download weight is. So you can save a lot of LI by reducing the poly count. But don't take it too far. I'm sure you have seen meshes that break down into a mess when viewed from a mdoerate distance - and the ones where you are asked to "increase your RendeVolumeLODFactor" to see properly. Those are meshes made by people who don't know how to make mesh. More specifically, they don't know how to control the LI so they just butcher the LOD models to get it down. You don't want to be one of those people.
3. Try not to combine large and small polys in a single mesh. For now that is. Experienced mesh makers can get away with it, beginners can't.
4. Balance the weights. I already mentioned that. Several small meshes will have a higher server weight than a single big one but usually much lower download weight. So you want to find the sweet spot where those two weights are about the same.
5. Use the normals. The normals? What's that? To make a long story short, with a mesh you can have "sharp" normals where the edges between surfaces are sgrap and clearly defined, and "smooth" normals where the edges are smoothened out and look rounded. Some mesh makers will tell you you should use smooth normals whenever possible to reduce the LI but that's not quite true. Which of the options give the lowest LI depends on a lot of factors.
6. Optimize for compressability. Or maybe not. We're into the advanced section here now. But I said the download weight is based on the compressed file sizes. You can save a lot of download weight by making the dae files as easy as possible for the server to compress. Typically you can get rid of 10-20% of the downlaod weight this way, sometimes even more. But this is where it gets a bit tricky. You need either a lot of practical experience or a lot of understanding how file compression algorithms work to really get much result here.

[Aquila Kytori]

Hi

The  “secret” to getting your DJ Equipment to have an LI of 1 as others have said is to create your own Lower LOD meshes. For something the size of your CDJ 2000 it will be the Low and or Lowest LoD mesh the will be effecting the Download cost the most. So these lower LoD models need to be using as little geometry as possible.

The CDJ 2000 is basically a box, with the top face a panel with buttons and displays.  In the lower two LoD meshes all this detailed geometry can be replaced by simple textured face. This Texture is called an Imposter.

In the example below you see the geometry of a High LoD mesh panel. Then below that is the geometry of the mesh that would be used in the Low and Lowest Lod slots in the mesh Uploader. Basically a simple box shape.

Notice how this lower LoD mesh’s top face has been given its own material. (As all LoD meshes must contain the same list of materials you will need to add this material to the High LoD mesh somewhere)

If you search in these forums you will find more detailed info on creating a lower LoD meshes that use Imposter textures.

https://community.secondlife.com/t5/Mesh/Tips-Needed-To-Maximise-Mesh-Detail-Whilst-Minimising-Land/td-p/2143879

https://community.secondlife.com/t5/Mesh/Best-Practice-for-pruning-a-lot-of-vertices-with-3D-text-Blender/m-p/3016414#M3

When rezzed in world this material face will be selected and given the Imposter texture. The simplest way to create the Imposter texture is to rezz the mesh in world, texture it as usual, then take a snap shot of the top face. Export to your hard drive and resize it smaller to something like 128 x 128 or 256 x 256 in your 2D editor of choice. It will only ever be seen at a distance so a larger texture size is not necessary.





To get the best results when using Imposters like this spend some time getting the snapshot/texture right expecially the brightness and contrast.

If you don't know already, LL provides a Beta test grid where mesh uploads are free, so experimenting and testing won't cost you anything but your time.

[Aquila Kytori]

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AdamZadig wrote:

One point I would like to make is that although I built it all in one go on blender I have given it approx 14 texture faces. And it uploads as 3 seperate parts instead of one even though I have it as one in Blender. 

 

---

Something I forgot to mention yesterday....... If the uploader is splitting your mesh into 3 separate parts you have lost all control over the LI cost ! You can't let this happen. Any lower LoD meshes you make will be useless.

Also, because LoD switching distances are dependant on size, (bounding box dimensions), the three 3 parts will be switching at different times..... which can look odd.

As already mentioned you need to go over your mesh and reduce the number of materials faces to 8 at most.

Keep in mind that the number of materials in a mesh object also effects the final LI cost

 

[AdamZadig]

Thank you to EVERYONE for your input. I read it all and made notes and applied it to my build. I was up until 5am remaking the build in blender and was able to get the prim count from 16 Li to 2 Li.

The tips I used were:

In Blender:  to reduce the texture faces to a maximum of 8. This allowed me to upload it as ONE object. Deleted surfaces not visible to reduce the triangles count (?)

In secondlife uploader: Upload in LOW physical and reduced the size of the object. 

 

Because it was a small CDJ 2000 which is the size of a playstation I kept the LOD low at LOW, and HIGH on the medium settings because even at smal distances it reverts to the medium LOD settings. 

 

You guys gave loads more things to consider so I will keep at it until I can get it to 1 prim!

 

 

[AdamZadig]

Hey, 

I was actually looking at land yesterday and saw one of your very low Li builds. A house and a warehouse! Both VERY NICE!

So cool that you should then reply to my thread!