Rigging Reflections

Over the last 2 weeks I have been working on Abigail’s rig, and subsequent skin. Rigging a character with a dress was not something I had done before, and took a bit of consideration to come up with a solution that would be friendly to animate with. I believe I have now achieved that goal. I have tested the model with a few poses that Abigail will need for her combat, and have found the deformations to be suitable. The true test will come in the next few weeks as I begin to block out the animation passes.

The process of deciding on rigging solutions took a few weeks. It was something I was considering thought the concepting and modeling phases. I was somewhat apprehensive about building the dress, a more complex feature, in to our character, however I believe when in game it will give our character a point of difference. Something that should, if done well, attract our industry professional target market.

I have done some rigging in the past, mostly standard rigs, with FK arms and IK legs. Nothing too out there, or too subpar, for someone of my experience. However when it comes to animating I want more than just a standard rig. Features I desire such as FK/IK arm switching or saving out poses were out of scope, were I to be building the rig myself.

To save time, and get the features, I wanted I looked to use an automated rigging solution. Rigging can be a time consuming task that is often automated in smaller, or tight turnaround, projects(Autodesk 2013). There are a few standard rigging tools to choose between. Initially I narrowed my options to CAT(Autodesk 2014), Mixamo (n.d) and Super Simple Rig (Super Rune, n.d). I wanted to explore these options, as I had used CAT in the past, and wanted to research some of the competing tools. Fairly quickly I rejected Mixamo due to its integrated skinning, and lack of extra features, I wanted control over the skin weights as I knew that would be integral to the successful deformations of Abigail’s Dress and puffy shoulders.

I then explored Super Simple rig, created by Super Rune (n.d). I was interested in this rigging solution as it was recommended by Steve, our animation lecturer, because of its animator friendly interface. I am also using this rig in my studio 3 project, and had found it easy to work with for short film animation. It has the features I wanted in the rig, FK / IK switching, options for extra custom bone chains, and also the option for twist deformation bones (although that is not really needed for this project because abigail is too low poly to take advantage of them). It looked promising, however getting the rig to work in Unity was a time sink I could not afford. Super Rune explains in a CG society forum post (2013) that his rig was designed with film animation in mind and is not intended for exportation to game engines. I spent a weekend testing it and would use it in the future for film, however for games I believe CAT is the best option.

I had used CAT before in my studio 2 games project. I know CAT is compatible with game engines, and again it has all the features I was looking for in a rig. It’s UI is a little more cumbersome than others, however since I have used it in the past It should not slow me down. The other advantage is that since CAT is used more widely there is more support if I run into problems.

Thanks to Ben, who recommended Rick Vicens (n.d) tutorial on advanced cat rigging, I learnt a few extra tricks in setting up my rig, such as using zeroed attributes. Creating the rig for the most part was simple, the biggest challenge again was the dress. When building the rig I could have made some extra bones, parented to follow the leg, however that would mean double keying at animation time, because the dress fell below the knee I would need to adjust those poses manually. I decided to weight the dress to the leg bones and to use morph targets to create variation in the way the dress sways. I know using morph targets is more resource expensive than pure bone animation. After discussing this with Lukas and Soren we should still be within acceptable resource use, since there is only one Abigail on screen.

Once the rig was created, skinning was the next challenge. Again the dress posed difficulties, in my attempt to create an efficient low poly character I had not built enough topology in to the dress, to smoothly stretch over the legs without clipping. This issue was not unforeseen as I was unsure of how low poly I could get away with. To resolve this I needed to add a few more loops around the body. This meant I could adjust some of the UV’s to sit a little flatter. Building the rig and skinning before texturing allowed us to test the model before we had spent too much time on the texture, a pipeline I feel I will employ in the future.

I was also able to restore my skin data that I had already applied. I had begun with the legs, since this was the area I was most concerned about, so losing this would not have set me back too far. Using tips from PEN’s(2009) forum post the process was able to save a few hours, a result that I was very happy with.

References

Autodesk (2013, July 10) [Video file] Meet the Experts: Learn how Zynga used 3ds Max in its Farmville 2 character and animation pipeline. Retrieved from https://www.youtube.com/watch?v=Esm3B4ab-r4

Autodesk (2014, December 17). CAT Character Animation Toolkit. Retrieved from http://knowledge.autodesk.com/support/3ds-max/learn-explore/caas/CloudHelp/cloudhelp/2015/ENU/3DSMax/files/GUID-EA1D6D09-A2CD-4204-8093-A7AE5EC5E333-htm.html

Mixamo (n.d). Mixamo Auto rigging solution.  Retrieved from https://www.mixamo.com/auto-rigger

PEN. (2009, February 24). RE: “Copy Skin Weights” for Max [online forum comment]. Retrieved from http://forums.cgsociety.org/archive/index.php/t-734093.html

Super Rune. (2013, February 27).  Super Simple Rig [Online Forum]. Retrieved from http://forums.cgsociety.org/archive/index.php/t-1095891.html

Super Rune. (n.d.). Super Simple Rig FAQ. Retrieved from http://www.superrune.com/tools/supersimplerig.php

Vicens, Rick. (n.d).  Rigging and Animation Workflows Using CAT in 3ds Max [Video file]. Retrieved from. http://www.digitaltutors.com/tutorial/575-Rigging-and-Animation-Workflows-Using-CAT-in-3ds-Max

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