Trails and tribulations of the Advanced Skeleton Plugin
In an attempt to lessen the load and skip what I'd heard to be a long process of rigging a character by hand through Maya's standard controls, I thought I'd used an automated plugin programmed to build it for me. I had heard of this plugin through Lipin Murali and Isaac Boardman as they had used this specifically for Rocket Dog. Isaac sent me the link and I got it set up on my PC nice and quickly.
There were some good tutorials on the Advanced Skeleton website and at https://www.youtube.com/user/AdvancedSkeleton but I found a more detailed step-by-step one on YouTube from https://www.youtube.com/c/AnimatorArtistLife which I followed.
The majority of the process was very straightforward, lining up half a standard human joint skeleton to the model, and adjusting the length and position of joints when needed. Once everything was lined up, including arms, fingers and root positioning, the advanced skeleton builds up the other half mirroring the joints onto the other side of the model.
After this stage the Skin Cage was calculated; this creates an area around the character that will be what moves when the joints are moved. This was followed by adjusting the skins so that there was nothing overlapping, articulating focusing on the finger area as them being so close together can cause problems.
An important step was adjusting the joint controls. As the model rig was generated so were the controls and some had generated inside the model making it hard to select and use them easily. Luckily Advance Skeleton has a tool to scale up the controls and adjust this when needed.
To help give extra control of the rig and how the movement will look, there is a step called Painting Skin weights. This is the process of adding weight to the correct areas, for example, the shoulder area is one that is likely to look warped when it is moved in the rig. Doing this helps control how this warp will look.
With that, the body was complete and bound to the model.
Moving on to the face there were many more steps for the build to be completed. However, I noticed there were issues with this setup from the beginning.
Above is what the set-up is supposed to look like. And below is what I was experiencing.
With one of the first steps being to select edges for where the eyelid would be going, I noticed it was not becoming a red blocked-out shape upon finishing it, as shown in the model above. I redid this step a few times just in case there was something I missed but I kept seeing the same result. Thinking it could just be a visual glitch and the system could still work for the overall build, I continued on to the mouth area where I also did not see a red area appear. With the same logic, I continued on and placed the dots around the eyebrows, jaw, cheek, chin and nose as the tutorials instructed. Another worrying sign happened when I did the steps for the forehead and instead of creating that green blocked shape between the vertices I selected, brightly visible on the model above, it created confused-looking green lines. It was definitely looking unhopeful for this step in the rigging process.
Once this was complete I should, in theory, be able to press Build Face Skeleton and it would automate the build, taking some time to go through some expressions and create the rig. Unsurprisingly this did not work. What happened after I clicked for the build to start was a very quick loading time, unlike the tutorials, and then a control appeared similar to the tutorials but only two controls within, one for each eyeball. This eyeball control worked which was great, but unfortunately, nothing else on the face had a control.
I tried a few things to get this fixed. Going over the whole process multiple times didn't get me anywhere so there was nothing I missed. I tried going through it with the unsymmetrical face settings, so doing the selections for the whole face rather than just the one side. This did change the result. I also tried going through the build one part at a time, I feature of the Advance Skeleton specifically there for if the automatic face build didn't work. This again got me as far as the eyeballs before not letting me get any further.
The Advanced Skeleton is specific in saying the model would work best if entirely symmetrical. My model had a slightly different typology on the face due to the hair blocking a larger area of the forehead. In my many attempts to fix the issue, I experimented by mirroring the face topology and this still didn't work. The plugin itself was completely up to date so I really struggled for a while to understand the issue.
I had decided to use the Advanced Skeleton Plugin as a way to overcome the large and long task of building the rig by hand, as I had limited time to complete many steps this term, this seemed like the best solution. Unfortunately, this actually ended up costing me a few days of trial and error and I definitely should have moved on to an alternative method sooner.
My solution to the face rig issue was Blend Shapes. It is something I was somewhat aware of from my research but I had dismissed them as something that could potentially take too long due to the idea that you would have to hand sculpt each expression. Looking at it in comparison to rigging the face by hand, however, I could see that this was the better option. It was a choice between trying something I had never done before, going through a 5-hour tutorial and hoping it would pay off, or sculpting in a way I was familiar with and simply changing out the expressions shown clearly in a few 15-minute tutorials. It also helped that I knew the exact expressions I would be needing from what I'd already planned out in the animatic, so I didn't need to make more than what I needed.
Another good thing about using Blend Shapes is that you can mix up your expressions and use a little bit of one to change another slightly. For example, I could use 0.5 of the surprised face and 0.5 of the scared/sad face to show a more shocked expression.
With expressions done that just left the eyeball movement to be rigged and I already knew a method that without a doubt worked for that. So the Advanced Skeleton didn't completely fail me with the face.
Closing Thoughts on the Rigging Step in the Pipeline
Whilst my experience didn't turn out to be the most efficient I think this pipeline of the automatic plugins and blend shapes is an interesting one.
Overall the Advanced Skeleton plugin was extremely effective at giving me a perfectly working body rig. The body has some great natural movement and has the option to use both FK and IK forms of movement. IK legs help the knees and leg joints move naturally and with the options to bend the arms with FK moves or an IK blend mode it really gives you the freedom to animate however you'd like.
For me, with my short film animatic all worked out with the knowledge of exactly what expressions I needed, the blend shapes were a perfect option to save the face rigging issue. If this were a rig for a longer feature or a TV show, however, I believe there would have needed to be a lot more options within the expression library. Even then, the blend shape seems to be a very convenient feature that could be applied to more items than just expressions so a very exciting thing to learn about.