SL Mesh Status Week 18

The latest news on the mesh front…


The Linden’s are telling us the mesh data format is going to change. This means the meshes uploaded to this point will no longer work. Mesh objects will have to be uploaded again. While this is a pain for many the change is made to get more stable mesh objects.

SL Mesh Changes

SL Mesh Changes

The changes have to do with renaming fields in the mesh data and removing some fields that are not going to be used. Additionally some meta-data is being added to allow mesh to rez faster. The document outlining Linden Lab’s mesh data format is started, per Runitai Linden.

These changes will roll out this week in ADITI. The changes will also necessitate a viewer change. So, you will need to get a new Mesh Project Viewer.

Also, not all areas of ADITI are the same nor are they running the same server software. The Mesh Experimental Sandboxes are: 20, 21, 27, and 28. Mesh Legacy areas are Sandboxes 7, 8, 14, and 15. All other Mesh Sandboxes are stable versions and for mesh upload. You can tell which you are in by looking at Help → About. In these areas auto-return is set at about a week.

Mesh Validation

To avoid bad uploads and deliberate griefing uploaded meshes are validated. This happens at the time of upload, when rezzing, and at region restarts. The Linden’s make changes at random times that may invalidate a particular mesh. These checks are causing some mesh objects to disappear after passing a previous validation test. So, if your mesh object disappears, you probably need to make a new upload of it.

If the new upload repeats the disappearing act, file a JIRA and provide a copy of the mesh. There are secure ways to provide files to the Lab without sharing them with everyone. Include the time the object disappeared. That allows the Lindens to find the right place in the server log.

Scrambled mesh with bunches of triangles running through each other can crash the physics in the simulator and the render pipeline in the viewer.

Mesh Swapping

We animate sculpties by swapping the sculpty texture. Many hope to do the same with mesh. That does not work with mesh. It crashes the sim. In the new viewers one will see that the Mesh Asset is gone. In fact it was removed a couple of weeks ago.

Why this is so has to do with how the server and viewer see objects. The viewer can asynchronously rez things and load their textures. The server has a problem doing that and running Havok. Runitai Linden explains it this way:

[…] for the sim, this is much more problematic than anticipated — especially with the presence of a running havok simulation.

The techniques we use for volumes just didn’t work for meshes — the result was leveraging a new threaded-rez pipeline to load meshes in a background thread before rezzing the associated object. A side effect of that decision is that objects can never change their mesh asset id.

The purpose in changing sculpty maps and mesh assets is to animate the object. When mesh is released it will not be possible to animate it. The Lab is expecting to add mesh deformations at some point to allow mesh animation. I wouldn’t count on seeing it any time soon.

Rigged Mesh

Making new mesh bodies and clothes uses Rigged Mesh. Mesh used for clothes and bodies does not need a physics shape, they use the avatar representation.

But what happen if one does no wear them, but instead drops them on the ground? Have you ever made something phantom and physical? It falls through the ground. Something like that would happen to mesh without a physics shape.

There will be a default shape for all meshes when the creator fails to supply or generate a physical shape. It is some type of simple convex hull.

Run Time Crashes

Some are having problems with the latest Mesh Project Viewer crashing. The problem is believed to be in the change to the VS2010 compiler. A fix is being rushed.

Current Work

The past week work has mostly been on merging mesh code with the main viewer and server branches. This allows serious testing of the code in the release channels, probably just the sandboxes to start.

Later this week or next the team will be able to return to fixing bugs/issues and adding some features, most having to do with mesh cost; upload, tier, streaming, etc. Most of the parts needed to calculate the mesh upload cost have been built. Now they need to be assembled and tested.

We still have no release date or mesh cost numbers. Soon  now…

2 thoughts on “SL Mesh Status Week 18

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