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Overview
The Construct3D Website.

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Download Construct3D videos in various formats.

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See students constructing in 3D.

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All project related publications and talks

Hardware Setups
We developed various setups for direct classroom use. Here is an overview.

Evaluations
An integral part of an educational AR application.

For Students
Construct3D related topics for Praktika or a Diploma thesis.

Contact
Hannes Kaufmann is the main developer of Construct3D.

Construct3D Hybrid Hardware Setups

To complement the diverse learning styles that are possible on the software side with practical hardware solutions for an educational environment we created various hybrid hardware setups. Realistically not all scenarios can be done in schools with equipment similar to our standard lab equipment of rather expensive tracking systems, head mounted displays and stereoscopic video projections. However, many components such as PC workstations with accelerated graphics and inexpensive projection systems are becoming feasible for classroom use. We are evaluating the following hardware setups:

The Augmented Classroom
Projection Screen Classroom
Distributed Desktop Setup
Remote Collaboration

The Augmented Classroom

The setup consists of two wearable augmented reality kits composed of back pack computer, stereoscopic see-through head mounted display with camera, and custom pinch gloves for two-handed input. One kit can be worn by the teacher, the second one is available for use by students. Both users can move around freely, since the kits are equipped with battery power for all devices and wireless LAN cards for communication. Furthermore, there is a small table, serving as a place for collaboration between the two users (see Figure 2, middle).
While this setup allows for first-class experiences on the students' side, the number of available AR sets significantly restricts the use in larger groups. This situation is somewhat analogous to the use of a blackboard in class: Either the teacher or a single selected student work on the blackboard, while the remainder of the class watches or works along on paper. During a lesson, students take turns at the blackboard. With the aid of an additional computer with video camera and video projection screen, we can mimic this classroom procedure by projecting a live (monoscopic) video of the users (teacher/student) augmented with their current construction on a projection screen next to the users for the remainder of the class to watch (Figure 1).

Figure 1: A teacher is working in Construct3D with the mobile AR setup while a live monoscopic video of his current construction is projected onto a projection screen behind him.

Just like in conventional classrooms, students can take turns at using the HMD and working in front of the class. To enhance the classroom situation for students not wearing an augmented reality kit, the overhead projection can also be used to view 3-dimensional content attached to markers. By moving a marker in front of the projection surface, its contents are shown on the projection (Figure 2).

Figure 2: Left: Demonstration of the mobile AR kit at a local science fair. Right: Interacting with models in front of a projection screen.

It is intended to be used by high school students and teachers in an interactive, collaborative manner and to blend seamlessly into an everyday classroom situation. Tangible, tool based interaction provides a simple and intuitive user interface. Support for multiple users and spontaneous collaboration encourages team work and simplifies supervision. The system integrates mobile augmented reality, collaboration, and a tangible user interface.
The Studierstube platform on which the Augmented Classroom is built brings together advanced augmented reality features in a unique way. A strong distributed shared scene graph infrastructure enables collaboration between independent mobile AR kits. Dynamic loading and sharing of multi-tasked AR applications between several hosts together with support for tool based interaction allow the users to load and share constructions by handling tangible markers, to print a snapshot of their work or to save it to file. The combination of these features into a single system allows the simple development and setup of a complex application like the Augmented Classroom.

Projection Screen Classroom

A popular semi-immersive technique is to use just a large screen projection shared by a group of users (in our case, the class), typically showing stereoscopic images using active or passive stereo glasses. The disadvantage is that since the screen is shared between the active user (e. g., teacher, demonstrator) and the observers, head-tracking is not useful, and consequently stereoscopic images are often severely distorted if rendered for an “averaged” viewpoint. In consequence, manipulation even with tracked input devices becomes indirect (comparable to screen and mouse manipulation) as objects do not appear aligned or superimposed with the users hands. Advantages of this approach include lower system complexity/cost, and the avoidance of cumbersome HMDs. Despite the shortcomings, projection walls are established techniques for semi-immersive group environments, and single-projector displays are affordable for classroom use.

Distributed Desktop Setup

Just like the hybrid AR classroom, this setup may use personal HMDs for realizing AR for the teacher and selected students. However, the students are all equipped with personal workstations displaying desktop VR watching the construction process on their screen. We built a desktop VR system using a FireWire camera for optical tracking and a standard consumer graphics card with shutter classes to get stereo rendering with optically tracked 6DOF input devices at a very low price (see Figure 3). The advantage of this scenario lies in the relatively low price for a personalized semi-immersive display: Students can choose individual viewpoints, maybe even manipulate local copies of the constructed object. However, a teacher can also choose a guided mode, e. g., by locking the students' views to the teacher's viewpoint.

Figure 3: Left: A user working with our desktop VR system. A FireWire camera (out of view) is used for optical tracking of the hand held props which are equipped with markers (see yellow ellipse). The image of the camera is used as a video background. Stereoscopic images are displayed on the monitor which give the user who wears shutter glasses the impression of working in 3D space.
Right: The virtual images of pen and PIP can be seen on the monitor (red ellipse) as an overlay over the video image. We are currently using a fully tracked glove instead of a pen for 3D interaction.

Remote collaboration

Although the advantages of co-located collaboration are lost, the same systems can be used for remote collaboration through a remotely shared 3D space. For example, a teacher can remotely advise a student at a homework problem by the same guided construction techniques as in the AR-classroom scenario, or multiple students can remotely work together. Each of the users has an individual choice of input and output facility, e. g., one user may wear a HMD, while another one uses a desktop AR setup. We are currently evaluating this possibility using our latest mobile AR hardware prototype as a test platform.

Contact: Hannes Kaufmann

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