Gaia Clary released a new tutorial for using Avastar to make Fitted Mesh clothes. The video tutorial was published December 24th on YouTube.
This tutorial gives you a quick education on how Avastar is intended to be used. I think it also clearly shows that weighting is going to be a more complex task. Using the old bones, old as in pre-Fitted Mesh era, and weighting one could kind of get by using just the avatar’s skin weights and a rudimentary understanding of weighting. That meant for a short skirt one was focusing only on the mPelvis, mHipLeft, and mHipRight bones.
Now we will also be considering the Butt, Belly, Right_Handle, Left_Handle, and Lower_Back. That gives us a total of 8 additional bones to consider. Weighting was complicated enough with 3 bones.
Also, I understand the mesh importer in the viewer will only import the first 4 weight values for any vertex. There seems to be some unpredictability as to which weight groups the Collada exporter places in slots 1 to 4 and which in later slots.
The weights we assign in Blender are not absolute. Blender uses them as a sort of a weighted percentage. Setting a vertex controlled by two bones, say the mHipLeft and mPelvis groups, each to 1.0 or 100%, depending on how you think of it, results in the vertex having 50% of its movement controlled by each of those two bones inside SL. It is that adjusted information that makes it through Collada, the importer, and into SL.
Thought of it another way, we can assign more than 100% weighting to any vertex. In the above example I mention 2 bones and thus I could assign 200% weighting. But, by the time we get to SL, that 200% has been changed so the viewer only ever figures out 100% of the vertex’s movement, so 50% per bone.
With 8 bones we could theoretically assign 800% control over a vertex. However the viewer will only ever want to know 100% of the vertex’s movement. It has to know where to put the vertex and draw it. So, each bone’s control is: 100%/8 = 12.5%.
Now think about not knowing exactly which 4 bones would make it through the importer. The viewer will only know about 50% of the movement we intended by adding values to 8 different vertex groups. If the left leg is moving forward and the right rearward and one or the other is dropped because it’s weighting is not in one of the first 4 groups, we will see very unintended movement.
This means we will have to be very careful to make sure we do not exceed the limit of 4 weight groups.
There is also the problem I pointed out in: Fitted Mesh Concepts. The BUTT weighting throws off the leg weighting I usually use. I was getting by with 3 bones. But, the pelvis area of the model now has weights from 6 bones. As best I can tell, any single vertex only has 4 weights.
While weighting did get more complex, we still only need to weight one model well and then use it for a starting point for our other models. While there is some initial pain added, it is not totally awful.
If you are thinking we should ask the Lab to allow more weighting groups to pass through the Collada mesh importer, you might want to rethink that. The more weight groups added the more difficult it is to predict the final result. I suppose some people will be able to handle more groups. I am having enough problems figuring out how to deal with 4 weight groups per vertex.
It is possible to accomplish all the steps shown in the tutorial in a Blender installation without Avastar. But, it requires a good knowledge of Blender and weight painting. Avastar just makes things easier and reduces the learning curve.
I have decided I do not want to try making a tutorial for accomplishing the same tasks without Avastar. It seems far too masochistic for me. I bought Avastar to avoid that work.