Moho Forum

I was hoping Vitruvian bones could finally solve the arm issue, being: I want to use smooth joints on arms, but can't, because I always had to keep the upper and lower arm on separate layers so that I could eventually have the lower arm be above the body and the upper arm below in some cases.

With Vitruvian bones I hoped that would be solved, since I could just switch bones with all the layers, alas…

If I want to switch the whole arm (3 bones: 2 for the arm, 1 for the hand) I'd have to use flexi-binding on all three bones including the hand, which means I can't use the smooth joint function which only works with two bones. Is there any way to make this work?

Here's Victor explaining how to use smooth joint on more than two bones: http://www.lostmarble.com/forum/viewtop ... =9&t=27158
You can use smooth joint with selective flexi-bind or layer binding, and even add point binding if needed, on a v-bone chain.

If you post/PM an example file of what you need, I can show you how to do it.

That's for images, it won't solve the issue with vector layers, also this will basically create two smooth joint / flexi-binding groups of two bones each, but to switch the whole arm via Vitruvian bones all three bones for upper arm, lower arm and hand need to be in the flexy binding group, which again will make it impossible to use the smooth joint for the bones.

There are other ways to deal with that. For example, my rig for Puss In Boots uses Smooth Joints in the arms, and they can wrap around the body in either direction. This setup was done years ago, so no need for Vitruvian Bones.

If I recall what I did back then, I placed one whole arm (using Smooth Joint binding) in front of the body, a duplicate behind the body, and I used Stroke Exposure as an animated mask to slide up and down the arm to reveal or hide regions progressively using a Smart Bone Dial. For the duplicate, this Stroke Exposure mask moved in the opposite direction, but otherwise stayed in sync. So, depending on the position of the SBD, the arm was either fully visible in front of the body, partially visible in front (lower arm in front, upper in back,) partially visible in back (lower arm in back, upper in front,) or fully visible in back. And since this was a stroke exposure animation, I had even had stages in between.

I thought this was a clever use of Stroke Exposure (I have my moments,) but I abandoned this setup in later shows because, in practice, this setup was way over-engineered for what I really needed most of the time.

Nowadays, I just create two copies of an arm, one in front of the body and one behind, with then use visibility to simply hide reveal the parts of the arms using an SBD. Just split at the elbow; the in-between stages are really not that useful. Alternatively, I'll use an animated mask the way I used Stroke Exposure, either by 'growing' the shape or just hiding and revealing sections. This is much simpler, and a variation should work fine for arms rigged using Smooth Joint.

Even my SBD controls are simpler now. I used to have separate SBD controls for each arm, but now I just use a single SBD to control every 'wraparound' possibility for both left and right arms. Realistically, there are only a handful of possibilities so this has been fine, and a single SBD is much quicker to setup and edit later.

There have been special exceptions for some characters and situations, but the above covers most 'everyday' situations I've encountered at work. (And I never know what crazy thing production is going to storyboard for us next.)

BTW, I don't use Smooth Joint often, but one thing I really love about it is how it lets me continuously 'spin' the arms at the elbow without tearing the arms. You can see me doing this over and over again in this reel...

My ‘Puss In Boots Interactive’ Demo Reel (2018)

arglborps wrote: ↑Fri May 07, 2021 5:55 pm That's for images, it won't solve the issue with vector layers, also this will basically create two smooth joint / flexi-binding groups of two bones each, but to switch the whole arm via Vitruvian bones all three bones for upper arm, lower arm and hand need to be in the flexy binding group, which again will make it impossible to use the smooth joint for the bones.

You can do the exact same thing with vectors. You just have to use two masks instead of image cropping and apply the same smooth joint to the mask vectors. Like Victor's example, both duplicates still only use the same chain of bones, so all those art layers are hidden with the v-bone. You can use selective bones for flexi-binding and smooth joint pairs on the same bones.

And since your masked duplicates are already separated (but still appear as one), you can place them either in front of or behind the body in different v-bone chains.

Another tip: If you use the Stroke Exposure trick, you'll want to disable anti-aliasing for the Stroke Exposure mask. Otherwise, you'll see a think matte line between the front and back mask edges. (This fuzzy gap is created by the AA; turning AA off allows the pixels to line more precisely.) Having no AA in the mask is fine because it's invisible anyway.

For arm segments that are simply hidden and revealed, you can get this matte line where the shapes are split. To overcome this, I just create a single point inside the elbow and force a slight overlap to hide the edge. This tiny hack is invisible in the final rendering.

I'll show how this works in a future tutorial. (FYI, I'm almost ready to release the first basics tutorials; will start releasing advanced tutorials shortly after.)

Edit: Speaking of AA, if you're rendering for compositing like I always do, sometimes there are compelling reasons to disable AA entirely, and you can still get the highest quality renders. I'll go into that in a future advanced tute.