what is highest polycount limit of model can upload in sl for different LOD levels ?

[bhuship]

Hi

I wish to create my own LOD of model to upload in sl. I wish to know what is highest polycount limit or triangle cout for High, medium ,low and lowest Lod. Please let me know. 

 

Thanks

[arton Rotaru]

http://wiki.secondlife.com/wiki/Mesh/Technical_Overview

LOD models will have to be lower, or equal in count as the LOD mesh above.

Also a very useful page to check out is: http://wiki.secondlife.com/wiki/Limits

[Drongle McMahon]

A model can consist of multiple mesh objects, and each object can consist of multiple materials (sets of faces which are allocated to the same texture). The upload format consists only of triangles. Any higher order polygons are converted into triangles by the uploader. So we only need to consider the numbers of triangles. A single object can have up to eight materials, and each material can have up to 21844 triangles. So the maximum you can have in a single object is 21844 x 8 = 174752 triangles.

However, the uploader uses a couple of tricks to give the impression that you can exceed these limits. First, when the triangle count for a material exceeds 21844, it secretly starts a new material. It can do this until you have used up all eight materials. So if you have an object with only one material and up to 174752 triangles, it will appear to upload normally. Internally it is represented as multiple materials, but as they all have the same name, they are supposed to always have the same texture. However, while you are changing textures, you may see some unexpected behaviour revealing the fact that there are multiple textures. These effects are not seen by other observers and disappear after a relog.

In the second trick, the uploader will also now accept a single object with more than eight materials, but it does this by internally splitting it into multiple objects, which can be separated inworld by unlinking. The way it does the splitting can have significant effects on the LOD behaviour and the LI. If you have both more than eight materials and some with more than 21844 triangles, you can get some very unpleasant effects in spite of the fact that the model will upload.

To avoid unexpected and undesirable effects it is always better to respect the limits of 21844 triangles per material and eight materials per object. You will always do a better job (better LOD behaviour and lower LI) of splitting materials and/or objects yourself than the uploader will, and sometimes it does a very bad job indeed.

Since you can have multiple mesh objects in your model, there is no upper limit on the total number of triangles in an uploaded model. However, there is supposed to be an upper limit on the total file size (see wiki limits) which would impose a practical limit. I have never tested that.

Finally, you should be aware that minimising the polygon count is one of the most important ways of creating efficiently rendered mesh that will avoid lag. High counts will be penalised by high LI for static objects and by lag for attached objects. It should never really be necessary to reach the limits described here for any object well designed for SL.

 

[Marcus Perry]

When did people start referring to texture faces as "Materials" ? Was that officially changed and I missed it ? Or Is it being accepted because everybody does it wrong ?

 

I'm not being nitpicky, I'm seriously curious.

[Drongle McMahon]

At first glance, at least five years ago (eg here). Can you explain why you consider "material" is wrong? I doubt if you will change my ingrained habit, but you can have a go if you like.

Inside SL the relevant entity is a list of triangles, a subset of those in a mesh, that are distinguished by a set of rendering attributes (textures, colours, etc.) normally known as material attributes. In SL and LSL this entity is called a "face", but that conflicts with the normal meaning of "face" in other contexts. (Hence the terms "SL face" or "texture face" to resolve the ambiguity.) In Collada, the same entity, that becomes the "face" in SL, is a subset of polygons that share (only) a distinguishing "material" attribute. In Blender (and, I believe, in other 3D programs) this entity is created by assigning a material to a subset of faces of the mesh. So the term "material" applies sensibly in all three contexts. In contrast, the terms "SL face" or "texture face" don't seem to have any sensible immediate meaning in the contexts of Collada or the authoring tools.

"Material" is not entirely satisfactory because the same set of material attributes can be applied to subsets of faces in different meshes, so that a specific "material" doesn't obviously refer to the subset of a specific mesh, although we often use it for that purpose. Also, there is some ambiguity with the use of "material" to encompass the physical attributes settable in the SL edit dialog. I think we  used to use the term "submesh", which doesn't have those drawbacks, but I guess it fell out of use because it didn't have any direct association with the rendering attributes that were the target of interest when referring to this entity.