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Architects, contractors, and their clients schedule regular meetings throughout the design and building process. These meetings play an important role in a building design by facilitating communications from different stakeholders with various expertise. During these meetings they take notes, make comments and draw on design documents brought by the architect. These documents may be plans, sections, or even, at the early stage of the process, 3D models. Later, when construction work has begun, the whole team walks around the construction site and once again comments and discusses issues that were not evident on the 2D documents presented in the earlier stages. Decisions can then be made and slowly the construction can continue.
However, today this process faces a new challenge: Many large architectural projects involve people from different places (sometimes even from different continents). It's not unusual to see a building in Germany designed by an American firm with the help of Japanese contractors. In these conditions, scheduling a meeting with all parties can be time consuming and not always possible.
To support this new type of collaboration and to address problems caused by time difference, we developed the Space Pen Project. Space Pen allows all the people involved in a building design process to leave comments, to draw on, or even modify 3D models directly over the Internet using their regular browser and a pen based interface. Any participant involved in the design or the construction of the building can log on to a secured web site, view the latest version of the design as a 3D model, walk virtually around it and make comments, or directly draw their suggested modifications on that same 3D model. The modifications and annotations will be saved and ready for review by other members of the design team at their convenience. Furthermore, because Space Pen is an asynchronous system, there is no need to schedule any rendezvous or meeting. Anybody can just log-on, make suggestions directly onto the 3D models and save them on the server.
Our first version of this system (called the Immersive Redliner) let people embed a note (displayed as a sphere) associated with a comment on a 3D model (a virtual Post-It note). We used VRML and Java EAI to implement the interactions between the 3D models and the back-end databases. To extend these functionalities and to enable people to actually draw or modify 3D elements directly over the Web, we now use Java3D, the 3D API provided by Sun Microsystems. Space Pen still embeds VRML models, recognizes and analyses them as if they were Java3D models; and handles all the user's interaction. In our first version of the system, we can draw any kind of shape or figure on the model, and also distinguish a drawing operation from "leaving a note" by identifying the user's click. Applying the same technology that Redliner uses to save comments on a distant server (cgi perl and java), Space Pen will be able to save and keep track of all modifications or added elements.
The Space Pen system goes beyond our previous implementation in that it features two interaction modes: a "leaving a note" by a click action and a "redlining on the spot" drawing action with continuous pen down. These actions trigger saving and sorting of the comments and modification drawing trace on a web server that allows later retrieval and display of the design history with "on site" modifications.
This paper describes our working Space Pen system, its functionalities, implementation details and use scenarios. The first part of the paper discusses the value of an online 3D sketching and annotation system for architects and designers. The second part of the paper outlines the rationale for choosing Java3D as the implementation platform, based on some key concepts behind Java3D. We discuss our approaches to create interaction and draw freely onto any surface of the 3D space. We also discuss the strengths and weaknesses of the new Java3D API: how well it can actually use VRML models, and the difficulty of analyzing these models for future interactions. We describe the current Space Pen sketching interface and how to recognize freehand sketches using diagrammatic parsing and scripting technologies and how we save them on a distant server. Finally, we discuss further research directions on online annotations of 3D models using pen-based input.