Tag: Mesh Deformer

The major topic of conversation during the course of the week has been the Lab’s announcement that they have released a new project viewer which can be used to make suitably rigged mesh garments deform to match an avatars shape as it is adjusted using the viewer Edit Shape sliders. It does so by using a modified version of the avatar skeleton and collision bones, as I was able to preview just before the project viewer was launched.

Since the Lab’s announcement, the response from various sections of the community have been mixed. Some have welcomed the new with open arms; some have questioned the overall flexibility of the solution compared to others, some have regretted the “loss” of the deformer and some have reacted in outright hostility towards the Lab.

In terms of the technical aspects of the solution, Karl Stiefvater (Qarl Fizz), who coded the mesh deformer, took time out to leave a comment on STORM-1716, the JIRA for that project, which reads:

Several people have asked me – this seems like the best place to answer.

LL’s assessment here is mostly good. In almost all situations, the simplest solution is the best one – and collision bones are indeed MUCH simpler than the mesh deformer. As I see it, collision bones have two downsides: 1) they are substantially harder to use for the person creating the garment and 2) probably don’t track as well to the avatar shape.

In the end, the evaluation must be made by the content creators who use the tool.

I will reiterate that the two-year delay and refusal to communicate are unacceptable.

This would seem to be a reasonable assessment. The use of collision bones is technically easier and, as noted elsewhere, is less reliant upon a large amount of code being added to the viewer which then needs to be managed and maintained as the viewer evolves, but it does have some drawbacks.

Commenting further on the subject in the Metareality podcast on Friday November 22nd, Karl added:

It [the avatar skeleton] already had a bunch of these bones in it for collisions. I have never, ever notices that someone shoots a bullet at me, and my avatar is fat, it actually hits me as if I were fat … It’s incredible that they put that kind of detail into it ten years ago. But, OK, they did. So my feeling – just to head-off any drama – is that it’s a nice solution. It is definitely a simpler solution, which is preferred in all software engineering, and probably all of life.

He went on to reiterate the fact that a downside of the approach is that it can making creating and rigging mesh garments harder, although as William Reed Seal-Foss observed:

Well, speaking from an artistic standpoint … and knowing how to rig, that’s already not fun, and it’ll make it more not fun, but it’s not going to be like you have to learn to do something new.

Pressed on the matter, Karl reconfirmed that while the Fitted Mesh approach may have weaknesses, he does feel that it is a good solution, noting, “Obviously, I’m invested with the one that we did, but this is good. This is good,” before also noting that as a technically simpler approach, Fitted Mesh is likely to hold-up better over time when compared to the deformer.

This still leaves the question as to whether personality may have played a part in the Lab’s decision. In the podcast, Kimberley asks Karl outright if he believes this to be the case, and he indicates that he believes so, stating, “I heard back from two different people inside the lab that told me that Linden Lab would never accept my code.” One would very much hope that matters weren’t influenced on the basis of personality; but the fact that the Lab previously rejected code from Karl for reasons which appeared tenuous at the time, would seem to be point to there being an issue of some description.

The debate over the pros and cons of each system will doubtless carry on in some quarters, as will the theories as to why one was selected over the other. In the meantime, feedback on the Fitted Mesh viewer is being generated and the Lab is working on updates. In terms of the technical aspects  / limitations of the system, it remains to be seen how they may impact things. As it is, the approach has arguably been used to good effect by the likes of Redgrave and other designers and has proven popular among consumers. Hopefully the same will prove to be the case as this solution proceeds through to a release status and as it is adopted by third-party viewers.

Related Links

• Making Mesh Garments Fit Better – Linden Lab
• Lab looks to make mesh garments fit better with the Fitted Mesh project viewer
• Metareality: Good Solutions
• Liquid Mesh: looking from all sides – August 2012
• Liquid Mesh: An assessment by Gaia Clary, August 2012

On Wednesday November 20th, Linden Lab surprised the Second Life community by announcing the release of the Fitted Mesh project viewer.

Project Viewer 3.6.11.283899 is aimed squarely at resolving the thorny and oft-critiqued issue of making mesh clothing fit a wide variety of avatar shapes, as the blog post itself notes, reading in part:

Since the introduction of Mesh to Second Life, creators have faced challenges fitting Mesh garments to the Second Life avatar. Because mesh objects are not resizable in as many ways as the avatar itself is, it has been difficult for mesh garment creators to provide garments that adapt to the shape of the avatar in the way that the image-based clothing layers do. While many creators have made heroic efforts to provide products in a range of sizes, and some have collaborated to define a set of standard sizes that work reasonably well for much of the user population, many have found that mesh garments just don’t work well enough for their avatars. Mesh garments also don’t move with the body parts affected by avatar physics.

Users have developed two approaches to address these problems:

• Rigging garments to the “collision bones” of the avatar skeleton (often marketed as “Liquid Mesh”). This works in current Viewers for some body parts, but there are some avatar shape parameters that do not have corresponding collision bones, so garments do not adapt to fit everywhere on the body.
• The “Mesh Deformer” project added code to the Viewer to dynamically compute how to modify each garment shape by looking at how the vertices of the avatar were changed from that of the female and male base shapes.

The Linden Lab development team has studied both approaches, and compared their effectiveness, maintainability, and performance. Neither approach completely eliminates the occasional need for an alpha clothing layer to prevent small parts of the avatar skin from appearing through garments, but both work quite well at resizing garments so that they fit the avatar and move naturally with it. While the collision bones method requires the creator to do some additional rigging, we have decided that because it leverages more of the existing avatar shape system it is likely to be the more maintainable solution and to perform better for a wider range of users.

While the two current approaches to fitting mesh clothing are mentioned in the blog post (“Liquid Mesh” and the mesh deformer), it’s worth pointing out that the “Liquid Mesh” solution is actually based on an idea first demonstrated by RedPoly Inventor as far back as June 2012 – and it turns out that his approach is the one that the Lab, via Oz Linden, acknowledge as the one that first got them “started down the path of using collision bones to do this.”

At the time Liquid Mesh first appeared, there were concerns as to its impact on the market and the potential for content breakage should it prove popular only for something like the mesh deformer to eventually arrive in Second Life, prompting calls earlier in 2013 for the approach to be blocked by preventing mesh rigged to non-standard collision bones from being uploaded.  At the time, the Lab remained silent on the matter, although many did blog on the potential pros and cons about the approach, including myself. Strawberry Singh not only blogged, but produced a video showing her testing a pair of boots she’d purchased which utilised the capability.

Prior to the launch of the Fitted Mesh project viewer, I was fortunate enough to be given the opportunity to preview it, and get to try out some sample clothing to see how it works. I don’t pretend this is a comprehensive review of the viewer, the new collision bones or skeleton; nor is it intended to compare / contrast the Lab’s approach to other methods. It is purely intended to provide an overview of the viewer and how suitably rigged mesh garments are handled.

The New Bones

As noted in the LL blog post, the project viewers includes an additional set of collision bones alongside the familiar set of bones. These are:

• BUTT *
• LEFT_PEC *
• RIGHT_PEC *
• LEFT_HANDLE
• RIGHT_HANDLE

* These bones are affected by avatar physics.

All of these bones, and the original avatar bones, now affect mesh clothing when the avatar shape sliders (Edit Shape) are manipulated, thus giving mesh clothing which is rigged to the avatar skeleton the ability to adjust with the avatar shape as the sliders are adjusted, thus leading to a better “fit” for the clothing.

Content creators are invited to begin experimenting with creating garments rigged to the new skeleton. To assist creators in this, a Rigged Fitted Mesh wiki page is under construction, which includes information on the existing / new collision bones, links to the male and female .fbx, .ma and .dae files, and basic instructions on getting started with creating fitted mesh, including a link to downloading the avatar skeletons and to additional external resources.

Do be aware that this wiki page is a work-in-progress, as is the viewer, and liable to both update and change.

The Viewer and a Quick Series of Tests

There are a number of important things to note before going too much further. The first is highlighted in the Lab’s blog post, and is this:

At this time, the new skeleton should be considered provisional and subject to change; we do not yet recommend selling or buying garments rigged to it. Since we may find reasons to improve it during this testing process, and any change to the collision bones will likely break garments rigged before the change, we want to make sure that we have a set of bones that we can all live with into the indefinite future before it is widely used.

The second is that as with RedPoly’s original approach and Liquid Mesh, the approach will not entirely eliminate the need for alpha layers – but then again, it’s unlikely the mesh deformer would have entirely eliminated them, either.

The third is that the viewer obviously will not work with either unrigged mesh or rigged mesh which does not make use of the new collision bones (or additional bones intended to work with the appropriate sliders).

As the test clothing passed to me was for male avatars, and presented some of the usual problems when used with a female shape (and given I have very few mesh garments in my inventory, unrigged, rigged, liquid or otherwise), Oz kindly popped over and gave an initial demonstration. As he was already wearing a mesh jacket, he quickly played with the sliders to give himself a more portly shape – with the result that his mesh jacket (as expected) no longer fitted. However, when he swapped to the rigged t-shirt in the pack, it more-or-less fitted off-the-bat.

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