Technical modernisation of the SUTAVE laboratory

Status:

completed 05/2022

Aims:

In 2008, the Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA) opened the SUTAVE Laboratory (Safety and Usability through Applications in Virtual Environments) with a VR interaction room. The room is designed as a circular CAVE project screen, 8 metres wide and 3 metres high. Projection onto the screen comes from three pairs of projectors. Channel separation of the images is based on the INFINITEC method, so that it is realised via different wavelengths of the RGB colours. Since then, a large number of projects have been carried out, especially in the field of human-system interaction. Some of the hardware (i.e. projectors and computers) was seriously obsolete and sometimes even failed, so that it had to be replaced to allow for future experiments with test persons and viewings of the VR lab. This made it necessary to upgrade the system to state-of-the-art equipment.

Activities/Methods:

Five new 3D projectors were installed, featuring an active shutter process that improved channel separation and reduced colour distortion. The conversion to five projection channels forming the overall image increased both the luminescence and the resolution of the projection as a whole. The result was a noticeable enhancement of the viewer’s immersion experience.

In addition, the entire computer system was upgraded, and older projects were converted and adapted to the new technology. Tracking continues to be handled by a tracking system from OptiTrack.

Results:

The upgrade was successfully completed. All previous projects based on the 3D development environment Vizard by WorldViz can still be run on the new hardware.

In 2018, the primary 3D development environment in the SUTAVE lab was converted from Vizard to Unity. The purpose of the upgrade was to switch to a state-of-the-art development environment. In addition, several projects were acquired that use an HMD (head-mounted display) for visualisation. Another purpose of the upgrade was to migrate all entirely HMD-based applications to the CAVE in the SUTAVE lab.

Unity itself does not currently have its own option for outputting an application in a cluster process via several displays (in this case, projectors). Although there are third-party manufacturers who offer commercial solutions to the problem, they were not considered for cost reasons. Instead, a proprietary solution was developed which can be expanded as the need arises. This means we can now present our own HMD applications in the CAVE without any major expenditure.

The hardware update in the SUTAVE lab led to a clearly noticeable improvement in presentation. The projectors are horizontally aligned and the entire CAVE has a screen diagonal of approx. 336 inches. Under the previous setup, the combined projection had a resolution of approx. 2,835 x 1,070 pixels, involving 3 pairs of projectors and resulting in a pixel density of 9 ppi (pixels per inch). The new system, on the other hand, adds up to approx. 6,330 x 2,400 pixels, coming from 5 projectors, thus raising the ppi value to approx. 20.1. This means that the visible pixel size has reduced to more than one quarter.

The brightness of the projection screen has also increased. While the luminosity of the previous projectors was about 10 cd/m² the new ones are about 30 cd/m², amounting to an increase of about 300%.

The active shutter method that is now in use ensures even better channel separation. This process involves the use of special 3D glasses in which the lenses contain liquid crystals that alternate between translucent and opaque. By synchronising the glasses with the projectors and the projectors with each other, the images for the right and left eye can be projected sequentially and can be passed on by the glasses to the relevant eye as required. The projectors operate at 120 Hz, resulting in 60 Hz per eye, so that switching is not noticeable to the user. Good channel separation is important to achieve a 3D effect and a perception of depth. Unless this happens, a ghosting effect occurs, among other things, whereby one eye sees parts of the image intended for the other eye.

In the future, an automated calibration mechanism will be installed. After a few hours of operation, due to thermal and hygric fluctuations combined with high resolution, this setup has proved to be more susceptible to errors in its overall projection, especially in overlapping areas. This is to be compensated through regular calibration.

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