Mesh (Content Creation)

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A polylist mesh, usually simply called a "mesh", is a 3D model generated from a complete list of data downloaded from the server. A mesh has amuch higher streaming cost than a prim or a sculpt but offers far more flexibility for the content creator.

Contents

Faces

A mesh in Opensim can have up to eight faces.

A mesh with more than eight faces can be uploaded but the uploader will split it into two or more objects and it's not very good at it so it's better to split manually before uploading.

Level of Detail

Each LOD model has to be created before or during upload.

Knowing how to make good LOD models is one of the most important, perhaps even the most important, skill a mesh maker for Opensim needs. The uploader can generate them automatically but the result is hardly ever satisfactory It's a balance: simplify the LOD models too much and you get the typical Second Life mesh that turns into a mess when viewed at a little bit of distance, don't simplify enough and you add a considerable extra load to the render engine. Do it wrong (or use the uploader's auto-generated models) and you get a mesh that both collapses at a distance and adds unnecessary render lag. Mesh geometry is by no means the biggest cause of render lag but it is still a significant factor and should not be ignored.

LOD model creation is a typical "minute to learn, lifetime to master" skill. Very few 3D artist know how to make great LOD models for Opensim but making perfectly acceptable ones isn't that difficult and making something slightly better than what the uploader usually produces is something most people with a little bit of 3D modelling experience can easily learn.

It's hard to find good information on the topic though, especially since the way Opensim (and Second Life) handle LOD is so different from how other game and virtual world engine do it. This is probably why even most seasoned professionals seem to struggle with getting it right.

Physics

The physics model is separate from the main visual models and the LOD models. See the links below for some guides how to make good mesh physics for Opensim.

Links

Guides

Lag: Geometry (prims, meshes and sculpts)

A short article on the differences in lag caused by prims, meshes and sculpts.

Second Life Mesh Physics 101

Not all of the info here applies to opensim since it uses a different physics engine than SL.

How to make good mesh physics

A similar article to the one above but more geared towards opensim.

Tutorials

Internal links

Content Libraries

Online repositories for meshes.

But before you upload meshes you didn't make yourself:

  1. Watch out for illegal copybotted objects! The meshes from the sites linked here should be safe but that's not always the case for meshes from other sources and even the best monitored public collection my accidentally include some illegal content.
  2. Try to avoid duplicate uploads! Every single copy of a mesh or a texture adds to the load both for server and client. It's not much but it adds up. If you can find a good upload of the mesh on the hypergrid, sue that one instead.
  3. Consider the polycount! General purpose meshes are not intended for realtime rendering and they are not intended to share rendering time with other objects. Because of this they often have very complex meshes with superfluous vertices and tris. Even "game ready" content may be too complex for the more crowded scenes we typically find in a shared virtual world.
  4. Try to make decent LOD models! Meshes not made specifically for Opensim and/or Second Life will never come with relevant ready-made LOD models. (If they do, it's a very strong indication it's a copybotted object.)
  5. Try to make decent physics models! Same as above.
  6. Check the textures! There are three issues to be aware of:
    1. Meshes made for other environments often use textures with a higher resolution than what we can afford in a shared citrual world. Consider scaling them down.
    2. Meshes not intended for realtime rendering may sometimes come with multiple small textures and/or duplicates of the same texture. If so, see if you can consolidate them.
    3. Opensim and Second Life have an unusually dark light setting compared to most other virtual environments. It is often necessary to compensate for this by making the textures lighter.

itch.io (game assets section)

Link: https://itch.io/game-assets (Confirmed 2023-05-26)

  • Content: Various, mostly models
  • License: Various

Wikipedia says: "Itch.io (stylized in all lowercase) is a website for users to host, sell and download indie video games, indie role-playing games, game assets, comics, zines and music." Much of the content is also found at OpenGameArt and/or SketchFab and it seems many game content creator regards itch.io as their main distribution channel and the other(s) as secondary one(s). This means there's a good chance you'll find new content here first. Most of the content is pay-what-you-like-or-nothing-at-all donationware, a few items are commercial.

OpenGameArt

An exceptional repository of permissively licensed content for game creation.

Outworldz

Content: All kinds License: Various Collection of textures, meshes, objects, avatars and other items. Licenses vary.

Renderosity

A marketplace for content for DAZ Studio, mostly commercial but also some freebies. The content is not supposed to be game ready and much of it is too heavy for real time rendering but it's still worth looking at.

ShareCG

A source for free animations, 3d models, textures, etc.

SketchFab

A huge collection of models. Apparently SketchFab was originally intended to be a resource for storing 3D models to be embedded onto web sites but many of the models there are also for sale or downloadable for free. Like all generic online 3D model collections, most of the content is not intended for games/virtual worlds and too heavy for real time rendering. There is still a lot there that can be used for opensim though.

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