Summary

I participated in a projection mapping development project for the university festival. I was in charge of developing a system to synchronize the video output from four projectors to cover the large and non-flat school building walls with images. This project was launched in April 2018 and lasted approximately eight months, from the concept proposal for the video content to the system implementation. On this page, I will describe the system I developed in the project.

https://youtu.be/fS7P2uIHhhg?t=483

みやこ祭 プロジェクションマッピング @miyakoFesPM2018

Background

In our university, volunteer students create a projection mapping work on a different theme each year and present it at the university festival. As a system developer, I joined the project two months before the university festival. I took over the system from my predecessor and maintained and updated the application functions.

Equipment

In this project, equipment dedicated to projection mapping was not used. Students were using their Mac PCs and projectors borrowed from the laboratory. Therefore, this spectacular show consists of the most common equipment you can see daily. On the event day, a sound system (public address system) was installed at the venue.

System Configuration

The system consisted of one main PC, five follower PCs, four projectors, and a PA system. The main PC and each follower PC are connected by LAN cable. The main PC is the controller that oversees all follower PCs. Follower PCs - A to C are responsible for playing the video from the projector, and follower PC - D is responsible for playing the sound data from the PA system. On each PC, an application created with openFrameworks, a C++ open-source toolkit for creative coding, is running, and command values can be communicated with each other via OSC communication. Each PC has video data in advance for each building wall. The projection can be controlled by sending commands from the main PC to all the follower PCs. The following command values can be selected: (1) confirm device connection, (2) play video, (3) stop video, (4) rewind video, and (5) enable/disable video output.

Device Connection Check Function

A connection check function between devices has been newly implemented because a failure of communication between PCs may cause a problem where the images of particular follower PCs are not played out. This function allows the operator to check whether data communication between the PCs will be successful in advance.

The structure of the newly incorporated connection confirmation function is shown below. The OSC communication protocol was used, which allows a string of characters separated by "/" to be sent as data. As shown in the left image, the combination of strings beginning with "/pmap" is used to verify the connection and control media.

As shown in the right image, in the connection check, the main PC sends an OSC message to each follower PC, and if a response is returned from the follower PC, it indicates that the communication channel is established. The status of each follower PC is displayed in the execution window of the main PC. As shown in the bottom image, if the connection is confirmed, "success" is displayed in green; if the connection fails, "failed" is displayed in orange.

Structure of OSC messages

Processing steps between main PC and follower PC when checking connection

Execution window of the main PC

Performance at the University Festival

The festival was held for three days, with three performances each day. We had nine performances in total. I was very happy that many people of all ages could see the works I was involved in creating. The developed system worked without any problems from start to finish, and the nine performances were completed without incident.

Experiences

• The experience of collaborating with experts in different fields to produce the work.

• The experience of having a large audience see the work we were involved in producing.

Future Tasks

The main PC can send OSC messages to all follower PCs but cannot simultaneously send packets to two or more. Therefore, even though the images appeared to start playing at the same time, there was a slight timing error. By improving the timing synchronization method between PCs, it will be possible to provide higher-quality shows.

Gallery