design machine groupUniversity of WashingtonSeattle WA USA 98195-5720http://depts.washington.edu/dmachineSketch That Scene For MeCreating Virtual Worlds by FreehandDrawingEllen Yi-Luen DoIn eCAADe 2000 'Promise and Reality'proceedings of the 18th conference on Education inComputer Aided Architectural Design in Europe,June 22-24, 2000, pp265-268Sketch that Scene for Me:Creating Virtual Worlds by Freehand DrawingEllen Yi-Luen DoDesign Machine Group, Department of Architecture, Box 355720University of Washington, Seattle, WA [email protected] the Web people can now view virtual three-dimensional worlds and explore virtual space. Increasingly, novice users areinterested in creating 3D Web sites. Virtual Reality Modeling Language gained ISO status in 1997, although it is beingsupplanted by the compatible Java3D API [1] and alternative 3D Web technologies compete [2]. Viewing VRML scenes isrelatively straightforward on most hardware platforms and browsers, but currently there are only two ways to create 3Dvirtual scenes: One is to code the scene directly using VRML. The other is to use existing CAD and modeling software, andsave the world in VRML format or convert to VRML from some other format. Both methods are time consuming,cumbersome, and have steep learning curves.Pen-based user interfaces, on the other hand, are for many an easy and intuitive method for graphics input. Not only arepeople familiar with the look and feel of paper and pencil, novice users also find it less intimidating to draw what they want,where they want it instead of using a complicated tool palette and pull-down menus. Architects and designers use sketchesas a primary tool to generate design ideas and to explore alternatives, and numerous computer-based interfaces have playedon the concept of “sketch”. However, we restrict the notion of sketch to freehand drawing, which we believe helps people tothink, to envision, and to recognize properties of the objects with which they are working.SKETCH [3] employs a pen interface to create three-dimensional models, but it uses a simple language of gestures to controla three-dimensional modeler; it does not attempt to interpret freehand drawings. In contrast, our support of 3D worldcreation using freehand drawing depend on users’ traditional understanding of a floor plan representation. Igarashi et al. [4]used a pen interface to drive browsing in a 3D world, by projecting the user’s marks on the ground plane in the virtualworld. Our Sketch-3D project extends this approach, investigating an interface that allows direct interpretation of the drawingmarks (what you draw is what you get) and serves as a rapid prototyping tool for creating 3D virtual scenes.Instant 3d world from a napkin sketchSketch-3D is a pen-based interface that recognizes simple geometric shapes in a two-dimensional view. To create anarchitectural space you draw lines and circles in a simple “cocktail napkin” sketch to indicate the placements of walls andcolumns. You select different colors for the elements you draw and the 3D world is created accordingly. Figure 1 belowshows the screen snapshot of this simple interaction.Figure 1: A floor plan drawn with Sketch-3D. Lines, circles, and spirals (left) are translated to create a 3D VRML world withwalls, columns, and view points, shown in a Netscape browser (right).Beside create a furniture layout in a space you draw symbols to indicate the locations and the types of furniture you like toplace on a plan view. For example, a configuration of a dinning table set is defined as four boxes (chairs) surrounding acircle (dinning table). Figure 2: A sketch of furniture layout plan produced 3D furniture objects in VRML format.After creating the world, you can use a VRML enabled browser to navigate and explore different paths and view points. Forexample, Figure 2 shows how a walk through the world is reflected by a series of circles on the original floor plan sketchthat indicate your path through the world. This two-way communication gives you the opportunity to quickly see the 3Dworld you’ve created. It also provides a “you are here” map that shows where you are on the sketched floor plan as youmove through the space. The sample rate remains constant and therefore the speed and acceleration through the world isrecorded and displayed as well.Figure 2: Your path through the VRML world (left) is reflected on the original sketched floor plan (right).ImplementationThe floor plan sketching part of the Sketch-3D program is built in Lisp, using our Electronic Cocktail Napkin drawingplatform [5]. The program recognizes simple floor plan symbols (lines for walls; circles for columns; spirals for viewpoints) and a translator module outputs a standard VRML format file that any VRML enabled browser can read. Theprogram assumes that the world is level and that the heights of all the sketched floor plan elements are the same. It simplyextrudes the walls and columns to a default height.The VRML file that Sketch-3D writes to describe the world’s geometry is augmented with a touch sensor and proximitysensor. These sensors are used on the client side to communicate with a Java applet running in the browser. The proximitysensor prompts the Java applet to continually report the browser’s view location and orientation; the touch sensor reportswhen the user clicks on an object in the world. The applet communicates with a Perl script running on a server, which inturn relays the view location and orientation information back to the sketching front end. This TCP/IP based architecturetechnically distinguishes world creation and path monitoring from browsing, although they can also run in the sameenvironment. Current and future workWe are working on several extensions to the floor plan sketcher that address obvious needs in our prototype. Mostimmediately, we are implementing a way for the user to indicate the height of the extruded walls and columns, by sketchingan isometric projection. We’re also exploring enabling a user to sketch walls directly into the browser as they would appearin the VRML world, augmenting the floor plan sketching facility that we report here. In addition, we’re interested in usingfreehand sketching to construct fully three-dimensional models. To that end, in another project in our lab we’veimplemented a 3D sketcher that uses the constraint