Below is quick technical note.
This video is originally made for the Japanese TV Show, “TECHNE – The Visual Workshop“. The every episode introduces one visual technique such as stop-motion, then challenges creators to produce a short video using that tequniques. I’ve called to appear on the program as a video artist, and my theme in this ep is to use “rotoscope”. I had been thinking about how to extend the notion of rotoscope, and finally came up with this “3D rotoscope” technique.
To explain it briefly, I made the 3d previs for rotoscoping in Cinema4D at first. It includes a 3d-scanned face with Kinect and geometrical forms which are not usual as a motif of clay animation. Then I rendered them as “depth map”, which represents a distance from the reference surface, such like a topographical terrain map.
Next, I set a pair of Kinect and projector right above the rotating black table(referred as ‘disc’). I made the app which enables to display whether heights of each point on a surface of the clay is higher or lower comparing with the depth map with colored dots. If higher, it represented as red. The lower one is blue. It becomes green when it gets nearly right. Therefore, the form of the clay almost corresponds with the previs if all of the dots turn into green.
I mean we can trace the 3d previs with a clay by repeating this more than 500 times. Generally speaking, clay animations tend to be more handmade-looks, and an analog one. However using such this workflow, I thought clays will move and metamorphose precisely like CG. In addition, I want to combine the highly automated system with such an old-style and laborious technique.
I used Dragonframe and EOS 7D for shooting stop-motion, openFrameworks for creating the shooting app. I adopt a Kinect V2, which partially works on mac.
Integration of Dragonframe and openFrameworks
Dragonframe only can send events by calling shell script with parameters, so I wrote the script which sends as OSC with Node.js.
I used ofxKinectProjectorToolkitV2 for transformation from 3D Kinect coord to 2D projector coord. I calibrated with this sample in the addon. It exports
calibration.xml which includes some coefficients.
The implementation of a transformation using the coefficients appears to be written
ofxKinectProjectorToolkitV2::getProjectedPoint(), and I referenced it and rewrote as the shader program to make it more efficient.
Converting to the disc coord
I realized a need for converting between the disc coord (whose origin is positioned at the center of the disc) and the Kinect coord (at IR camera) so I implemented the system to set an X-axis and Y-axis on the disc, like below gif:
It was so tiring😭
I made the mount for the projector and Kinect. Modeled with Fusion 360, and cut the parts from MDF with my CNC milling machine. Honestly, it was most exciting time than any other processes lol
As you can see, I had planned to control also the rotating table, but it was failed because of a shortage of torque of a stepper motor 😨 I have to study about mechanic more.
Incidentally, I wanted to mix iron sand and a glitter into the clay to make it more variant texture. Below picture is the experiment for it.
And I also found the problem that the measurement of depth is interferred by a man who stands very close to a Kinect. Not to wiggle the measured heights, we have to go on standing the same position. After all, we had referenced the guides and contours which rendered with Cinema4D additinally. I’d like to find a smarter way.
Although there’s many reflection points, it was so interesting to make such an experimental work with experimental workflow.
I think Kinect community should be hotter. Until a few years ago there’s so many digital arts using Kinect whose visual looks like “Minority Report”, and it had got out of date. Many creative coders are now working on VR or deep learning field. However, I think there should be a lot of undiscovered ways to use a depth camera, whether using its depth image to visualize directly or not. So I’d like to go on digging it.
And I really don’t want to touch a clay anymore, at least 10 years lol