Exhibition: Calibration in motion capture and bumblebee: Bumblebee Apocalypse
The exhibition is held for two weeks in April 2022 at Kuutio space, the second floor of Helsinki Central Library Oodi (Helsingin keskustakirjasto Oodi). The exhibition is supported by the Master’s Programme in Animation, School of Arts, Design and Architecture, Aalto University, Finland.
“In general use, calibration is often regarded as including the process of adjusting the output or indication on a measurement instrument to agree with value of the applied standard, within a specified accuracy.” (Calibration – Wikipedia, 2022)
As a RE: ANIMA student studying a course Research-Based Animation Film Production – Going Virtual! at Aalto University, I have an opportunity to study and experience motion capture from scratch. The project Bumblebee Apocalypse began with my observation of the motion capture process when my groupmate and I played around with a motion capture suit, sensors and a monitor. A step in the process of motion capture that intrigued me is the process of calibration.
When we are moving in motion capture, our motion from the tangible world is captured into a digital format and be screened on a monitor. However, the first time we tried, I noticed a difference in the motion between my friends moving in front of me and my transformed digital friends on the monitor. Even, they came close to each other or came to touch hand-by-hand, they cannot touch each other on-screen (You can see an example in the photo below). It is called a deviation that can be occurred due to the process of transferring information. To fix it, we need to take a process of calibration. Somehow I found that the deviation occurred due to the inaccuracy of information in digital is captivating. My friends were digitised into information and transformed into another appearance with deviated motion, however, the reality of weight and gravity of motion still appear. The combination of both gave me a fascinating feeling.
Calibration in motion capture
To fix the deviation (inaccuracy information), we use a calibration process in the software named Xsens. The software provides a few instructions as there is more than one way to calibrate. We learn to calibrate by T-pose method. Basically, we need to pose and move following the steps the software gives to us. Starting with standing still, holding our hands up as T (T-pose), walking straight and moving around. It will take a little time in each step to calculate the information between the layout of the surroundings (space) and the properties of body profile and action capacity (our body). The result of the calibration will be shown afterwards. The result can be varied depending on factors. The quality of calibration can be poor due to an unstable signal from a sensor attached to the motion capture suit or due to an unstable movement when we need to stand still as these will interrupt the process of calculation. When the quality of the calibration is good, it means the deviation is acceptable at a certain point. (You can see a few examples of the calibration results in the screenshots below.)
Calibration in bumblebee
While I am researching the calibration process, I came across an article: Bumblebees perceive the spatial layout of their environment in relation to their body size and form to minimize inflight collisions (Ravi et al., 2020). The article investigates the interactions of the bumblebee’s body with its surroundings. The study by recording and analysing over 400 flights of bees flying through gaps suggests that the bees calibrate and reorient their body and movement: heading/yaw orientation while in flight to avoid collision as wing damage or a crash landing can adversely impact their life span. I found this study is so amazing. Since I was a child, when I saw bees buzzing or bumbling I did not understand what are they doing but now I do understand them more. The resonance of the calibration in different fields: motion capture and nature (bumblebee life) inspires me to dive further into the motion of the bee. Exploring the bee movement with my understanding of motion capture as a concept to develop my aesthetic expression is what I will share with you in the next topic below.
Colour oil painting on glass animation as a medium to explore the T-pose process in motion capture
One of the animation techniques that I used to explore the process of calibration and would like to highlight here is the colour oil painting on glass animation. In this exploration, as I had never worked on this technique before, I had worked with Bahar Kiamoghaddam who has experience in the oil painting on glass technique. I had a plan in mind in advance to focus on the T-pose step in calibration with oil painting as I found it might be interesting due to the characteristic of the oil, the fluidity. When we are being in the T-pose step, we need to be still as possible to let the computer calculate the sensors on the motion capture suit, but if I try to animate a bee doing the T-pose with oil, it might be even harder than usual to be still and get a good quality of the calibration.
When Bahar and I started working, apart from the experiment I had an idea to work on, I also needed to learn how to work on this technique. So, we came up with the idea of simultaneous painting. We called it “Animation Synchronisation”. In motion capture, If there are two persons wearing motion capture suits and are being in the process of calibration, they need to stand still, at the same time and in the same pose as possible before recording. It happened the same to us while we were animating on glass in the under camera technique. The first thing was that we needed to animate the bees hovering trying to be stable by using colour oil. Then, we needed to paint at the same time and waited for another person to finish the painting and take a shot frame by frame. The process of calibration happened in the studio that works on the relationship between the space and our body moved into another space. The studio was changed to a space of a plate of glass. Our bodies wearing the motion capture suits were changed to animators’ hands. The sensors attached to the suits were changed to the brushes attached to the animators’ hands. The process of calculating on a computer was changed to the process of painting on glass. In a metaphorical way, for me, while I was working with Bahar, it seemed like we were doing synchronising diving in a diving sport. Two divers performed the exact same pose simultaneously. It seemed like a meditation pair.
Some photos and images of the Bumblebee Apocalypse making process
En.wikipedia.org. 2022. Calibration – Wikipedia. [online] Available at: <https://en.wikipedia.org/wiki/Calibration> [Accessed 1 April 2022].
Ravi, S., Siesenop, T., Bertrand, O., Li, L., Doussot, C., Warren, W., Combes, S. and Egelhaaf, M., 2020. Bumblebees perceive the spatial layout of their environment in relation to their body size and form to minimize inflight collisions. Proceedings of the National Academy of Sciences, 117(49), pp.31494-31499.
Bastamow Tanja, my teacher who allowed me to work and develop the project in whatever I want to.
Aalto Bjarke, a studio technician at Aalto who taught and helped me in motion capture.
Bahar Kiamoghaddam, my classmate who shared her animation experience with me in the project.
Delanyo Sabblah, Maryam Khalilzadehbin and Tsai Yichin, my groupmate who always support and encourage me to finish the project.
If you are in Helsinki in April, please feel free to come and stop by to see the Bumblebee Apocalypse.
Exhibiting VR experiences from the Re: Anima Going Virtual workshop
Saturday – Sunday, April 9th – 10th and Saturday, April 16th
11am. – 6pm. Oodi Central Library, exhibition space Kuutio, 2nd floor.