Category: SL Tech

The following notes and audio were taken from the weekly Bento User Group meeting, held on Thursday, February 25th at 13:00 SLT on Aditi. For details on each meeting and the location, please refer to the Bento User Group wiki page. Note that the audio excepts are not necessarily chronological, one to the next. Items such as wing bones were discussed at a couple of different points in the meeting, but the comments have been drawn together in an attempt to present a complete discussion of the subject; however, the subjects within each audio extract are provided in the order the discussion proceeded (i.e. the initial part of the discussion on wings is presented first, and the that later additional discussion presented at the end of the audio).

This was a short meeting, with the primary topic of conversation being finalising the Bento  skeleton in terms of additional bones and bone sets, following the recent survey (see my week 4 update).

Additional Tail / Limb Bone Sets

Vir indicated that he, Cathy Foil and Matrice Leville have been discussing a couple of ideas. The first is to cull some of the additional wing bones to produce a second set of “tail” bones, which could then be used for a variety of purposes, including creating additional limbs, or a new limb and additional animation options on the existing tail, etc. This approach would see each of the tails have 5 bones, compared to the current tail having six bones.

The second idea revolves around creating a pair of new limb bones using bones taken from the wings, and which would share the same mPelvis anchor point within the skeleton along with the existing tail (which would retain its existing 6 bones). This would simplify the creation of hind legs on avatars, allowing the tail to be moved”backwards” with them. At the same time, it would mean the additional limb bones could also be used for other purposes, if required.

This sparked a discussion on what might be the optimal approach to additional bone sets, naming conventions and whether any additional bones were in fact required, given there is now the ability to translate bone positions as well as rotate them. Vir agreed that naming does need to be considered, as that using terms like “tail” should mean the bones are limited to that particular use.

Concern was also raised on whether adding additional bone might add to the Bento time frame and if there might be other impacts. With regards to the latter, Vir indicated his hope is to run a stress test once the skeleton is finalised.

Other suggestions have been to simple add further bones to existing sets – such as with the hands, as suggested by Gaia Clary in the forums, although this has seen been seen as perhaps not as required as originally thought. Vir also reiterated that any additional limb bones could be used for arms as well as legs,

There has also been some discussion on the forum concerns limitations within the wing bone sets, which could be solved through the addition of wing “fingers” which would allow better animation of bat / dragon wings, with an explanation on how provided by Teager, who also explains the differences involved in animating such wings and those of birds.

Overall Status for Skeleton

In terms of any consensus for additional bones, it is Vir’s view that there is slightly more interest in having additional limb bones rather than a “two tails” approach, together with additional bones for wings (which could also be used for things like ears, etc.).

Vir will be taking this into account when defining the final skeleton, which he hopes to have available for people to review and test by the next meeting. However, he did warn that the overheads in getting the work completed, tested and signed-off might impact on this target, but it is one he’ll push for.

Issues Update

Additional Spine Joints

Vir is investigating problems with adding extra spine joints in the avatar, and has come across two issues. The first is that doing so can cause the current version of the Bento viewer to crash, although he believes he has a fix for this problem. The second, and more serious issue, is that additional spine joints, whilst working for mesh avatars, it will break the rendering of the default avatar. This appears to be a complex issue, and Vir isn’t confident it is one which might be fixed in time for the initial Bento deployment.

Avatar Deformations

Dan Linden continues to try to hunt down the cause of avatar deformations (BUG-11157). It has been noted that this is a complex problem, involving multiple factors – something which makes it hard to reproduce in a consistent manner. Following investigations, as I’ve previously noted, one causes appears to be scripted deformers which can have an adverse impact on avatars, in that they can continue to run when changing from one avatar to the next, causing the newly worn avatar to deform when seen by others.

However, the issue seems to be slightly broader than this, in that it appears a deformer used by one avatar can appear to impact another avatar when seen by others, whether or not that avatar is using the Bento skeleton.

An example of this occurred during the meeting, when Dan Linden, who was using the default avatar skeleton, arrived just as someone else was swapping avatars using deformation scripts. The result was that for myself and another attendee at the meeting, Dan’s avatar appeared deformed when viewed using the Bento viewer, while others who arrived a little later saw him normally. However, even the circumstances under which this situation occurred seemed to vary when put to a short test following the meeting, highlighting the fact that determining precise causes remains difficult.

Useful Links

• Project Bento overview – this blog
• Project Bento Knowledge Base article – Linden Lab
• Project Bento Skeleton Guide – Linden Lab
• Project Bento Testing – Linden Lab
• Project Bento discussion forum

The following notes and audio were taken from the weekly Bento User Group meeting, held on Thursday, February 18th at 13:00 SLT on Aditi.  For details on each meeting and the location, please refer to the Bento User Group wiki page. Audio extracts are provided, however, due to circumstances beyond my control, I missed the first 20 minutes of the meeting, so the following update is not a full summary of all that was discussed.

The Default Avatar Mesh and Bento

An area of concern regarding Bento is that while custom-built avatars can make use of the new Bento skeleton, and some work has been done on making some of the appearance sliders for the default avatar mesh compatible with Bento, there is next to no way at presents for the default Second Life avatar mesh to make full use of a Bento extensions. Much of this wouldn’t actually matter,  given that many of the circumstances where the new bones are being used would likely require the use of a custom mesh avatar. However, there are two noticeable areas where the it does have an impact: hands and faces.

Essentially, Bento introduces 30 bones into the face and 30 bones into the hands. However, these cannot currently be leveraged by the default avatar mesh, as demonstrated in the first 20 seconds of the video below.

As such, there has been discussion over the last couple of Bento meetings on ways in which this might be addressed. However, there are significant problems in trying to make the existing default SL avatar compatible with the Bento skeleton. One of these is that the default skeleton is designed in three core sections (head, upper body, lower body), each of which can only be rigged to utilise a maximum of 15 bones.

This means that trying to rig the default avatar to make correct use of the Bento skeleton additions isn’t that easy; the head and hands, for example, simply cannot support the number of bones offered by the Bento project. A further complication as that when it comes to facial expressions, the default avatar uses morphs rather than pure animations to achieve various expressions, and these could conflict with animations which utilise the Bento bones.

One solution would be to completely overhaul the default avatar or replace it. However, this is a massive undertaking, and one which could easily result in a lot of existing content breakage, as such it is not something the Lab is entirely sanguine about doing. Another idea put forward was for the Lab to provide two default heads, one utilising the default morphs and the other Bento bones and their associated animations. However, the limit of how many bones the default avatar mesh can support made this idea a non-starter.

Cathy Foil summaries the discusses on the avatar head, which occurred prior to my arrival at the meeting

During the discussion, Vir and Oz revealed that having the default avatar make use of the Bento skeleton is something the Lab has been pondering. However, it is not something that will be implemented during this initial phase of Bento due to the amount of work involved. However, it could be looked at as part of follow-on work from Bento.

Vir and Oz Linden raise the potential for Bento follow-on work to provide a means of making the default avatar head and hands more compatible with the Bento bones

That the Lab are considering trying to make some changes to the SL default avatar to leverage Bento capabilities lead to the suggestion by Medhue Simoni that perhaps the Lab should at the same time more broadly overhaul the avatar to provide a consistent set of vertices and weights throughout.

The idea here would be to present an avatar form which content creators could more readily use to model and rig fitted mesh items to a single, consistent set of vertices and weights, rather than each having to work to their own weightings. This would allow fitted mesh clothes to work more precisely with the avatar appearance sliders than is currently the case, and thus provide a more consistent and better feature set going forward.

The problem here is again exiting content breakage. One suggestion for dealing with this, put forward by Cathy, is that if the Lab decided to go the route suggested by Medhue, they could need to provide two default avatars, which users could swap between as needed dictated, by means of something like the gender change options currently found in the avatar appearance panel.

Comments on a wider re-working of the avatar skeleton

Appearance Sliders and Bento

As noted above, there has been some work completed on hooking some of the Bento bones to the appearance sliders – notably around the head and hands. Now that the updated skeleton is moving towards a final design, the hope is that perhaps more bones within it can be linked to the sliders.

Vir and Cathy on Bento and the appearance sliders

Continue reading “Project Bento User Group update 5 with audio” →