Second Life News 2013-9

Server Side Avatar Baking – Nyx Linden gave us a bit of information about the results of the Thursday pile-on test at the Content & Mesh meeting today. The Linden goal was to collect data and that they did. The outcome is that when SSAB works, it works really well. But, it doesn’t always work.

Content & Mesh Meeting 2013-9

Content & Mesh Meeting 2013-9

The pile on test gave them new data on the known bugs and revealed a couple of new ones. Friday was spent analyzing the data. Now they are moving forward on fixing the problems. There will be another pile-on test, may be this week. But, we will have to wait and see how things go. 


SUN-38As users of kneel/lay/sit animations and tiny/giant avatars, we need a way to change the body size in SSB sims. Henri Beauchamp filed this JIRQA item and alerted me to it. It also came up in the Content & Mesh meeting. You can probably read this item. Check to see if you can and if you can then click Watch.

This problem gets complex. Third Party Viewers (TPV) usually have a Z-Offset… meaning we can adjust the distance from the avatar to the ground. With some shoes this is very helpful. But, it is most important with petites and giants. Often they cannot look right when walking without it.

NOTE: See Henri’s comment below for a better explanation.

Full body mesh avatars use the Z-Offset in the mesh importer to make adjustments so the feet reach the ground. But, with the Server Side Avatar Baking (SSAB) changes something has broken.

Along with getting the height while walking correct, there is the problem of getting animations to work correctly. Often when a petite is sitting, the petite is floating above the seat. This JIRA is about getting that type of offset problem resolved fixed.

When asked about this problem Nyx Linden responded, “I have many thoughts – it hasn’t escaped our notice. We’re considering a couple different approaches – ask again next week? 😀

So, the Lindens are considering fixes for the problem. As of now they are not ready commit to a fix and so are unwilling to say what they are thinking. But, they are thinking about it.

You can test your animation, petites, and giants in the Preview Grid (ADITI) in the Sunshine regions. You will need to use the SSAB Project Viewer to avoid avatar render issues.

Flexi Prims

Some questions were asked that lead to a discussion of how Flexi Prims work and whether that qwould ever be possible for mesh items. Nyx took some time to explain how flexis work.

Nyx, “Prims are created by extruding a shape along a “path” – for example a cylinder is a circle extruded along a linear path. That path is a series of points – when you set something as a flexi prim, the parameters of its motion are sent down to the viewer. That makes a “spine” that your viewer can animate, but at a [computational] cost.

Normally objects don’t change their geometry very often, so we can save geometry data in graphics memory. Flexi-prims have to constantly update so we have to constantly re-generate that geometry data [and reload it to the graphics card].

Mesh objects don’t inherently have that path, so they [will can]not be flexi.

Also the computation is costly, so we will not likely turn it on for arbitrarily-complex content (prims have a limit to how complex they can be).

So, we are much more likely to see custom arbitrary skeletons/armatures that we can animate before we see flexi-mesh. Flexi-mesh will create far too much viewer lag.

More Land Impact Cost

People are still having problems figuring out why some items cost what they cost to upload and have the Land Impact Cost they have. I know that if you have not read about how it works and followed some the discussion here and in the SL forum you are VERY likely to be confused. There are little quirks here and there that can drive up costs. Dodging them requires learning about them. You can read the Mesh section here for lots of information.

But, a suggestion came up that may help. One would be to have the viewer print out a list of the individual costs of items in a link set. That idea has some interface problems if one were to attempt to display the information on screen. A link set can have 255 items. An alternative may be to print the results to a text file saved to disk.

Another idea is to allow the More Info display in the Build Panel to show the results for each linked item is selected when Edit Linked is enabled.

Either of these would help in tracking down problems with uploaded mesh items and link sets with mesh and prims.


VWR-28177Enable Prim physics-shape-type physics weight display in upload floater.

The change requested is described as: Presently the mesh importer dialog retrieves the download, server and physics weights from the server and displays them to the user so that a model’s land impact can be evaluated before committing the upload fee. However, the physics cost is only shown for the model with the default physics type “Convex Hull”. Since many models are intended to have physics shape type “Prim”, and require that for proper collision behavior, this limits the usefulness of the displayed information. The user has to guess what the physics cost will be and has to spend the upload fee to investigate the effects of changes on the actual weight.

This change would make it easier to see the cost of mesh items one plans to upload as type Prim. Unfortunately, this item is not viewable by all those that would like to vote on it. If you feel passionately about it, file your own JIRA request for the feature and refer to VWR-28177.

I-Bit Alpha

VWR-6713Allow Alpha Channel of Textures to be used as a 1-bit Mask (Alpha Masking).

Described as: Ever notice that the Linden trees have no trouble with alpha sorting? It’s because the alpha channel in those textures are being treated in a 1-bit format. The z-buffer is able to utilize them. So parts of the texture are either 100% opaque, or 100% clear. (Semi-transparency is not an option.) The Second Life client has the ability to do this already built into it. There’s so much potential there, but we have no way of tapping into it!

This item is going to get handled in the coming Materials System. See: Material Data in the SL Wiki. Scroll to the bottom and look for: Additional Parameters. Check out the section on Alpha Mode. It looks like some nice flexibility is being added.

This will allow us to make our transparencies work and look much better.

Shape Keys

There is a thing about shape keys that continues to go around. I’ve written about Liquid Mesh and Redpoly’s  Collision Bones as ways to make attached rigged mesh conform to the avatar shape. That came up again at this week’s Content and Mesh meeting.

Nyx responded to the questions about using shape keys, “I don’t think we have any mechanism right now for manipulating shape keys, nor is it in our internal mesh format.  Collada is our import format, but we don’t support every feature that Collada specifies.

It’s an interesting feature request, but would take a decent bit of work – could you write up a feature request JIRA with specifics of what that would look like?

I doubt any of these feature requests will go anywhere until Oz Linden gets people to work on the Avatar Improvement Evaluation. Also, Nyx commented on why going down the Shape Key path would be a poor idea, “The deformer project is trying to take those standard morph targets and allow clothing to be modified by them. Creating a system where you can upload meshes with arbitrarily defined shape keys and then providing an interface for setting those would be tricky.

So, I have very little hope of seeing Shape Keys go much of any place… even of the Mesh Deformer is stalled for now.

3 thoughts on “Second Life News 2013-9

  1. the javascript snowflakes are so distracying and visually disturbing i will refrain from further visits to the site

  2. Your description of SUN-38 is incorrect: the Z-offset is used to correct sitting (on ground) kneeling, crawling, crouching, laying animations, as well as many animations played by pose-balls (and the furniture using them) that don’t let you adjust the offsets. It applies to *all* avatars as is the result of the fact the root joint for avatars is at the level of the pelvis and how animations are adjusted by the server depending on the avatar height (and more precisely the pelvis to feet length): standing animations are properly adjusted for any avatar shape and shoes (the calculation made server-side to adjust the root joint height above the ground is designed to auto-correct standing anims), but of course, for a sitting anim, the change in the pelvis to feet length is irrelevant and the correction automatically applied by the server makes your avatar either float, or sink into the ground whenever its pelvis to feet length differs from the one used by the designer of the anim.

    The X and Y bounding box sizes for the avatar are also ignored by SSB sims, and this causes an issue for tiny and giant mesh (or prim-based) avatars for which you can’t adjust any more the shoulders width (making it, for example, impossible for a tiny avatar to walk between a chair and a table while its size would should allow it), and (less important) the rib cage thickness.

  3. Pingback: Cajsa’s Fast Five: February 27th | Its Only Fashion

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