VFXWorld presents a new excerpt from Building Interactive Worlds in 3D by Jean-Marc Gauthier. This months excerpt looks at using the virtual camera for The Diner project with the help of Fabien Barati and Zach Rosen.
This is the latest in a series of excerpts from Building Interactive Worlds in 3D by Jean-Marc Gauthier.
The Diner project is inspired by a conversation between two characters inside a small bar. The movement of the virtual camera, called the Dialogue camera, follows the intonations of the viewers voice or sound level in the physical space of the installation. The following conceptual process evolved from notes from a discussion between Fabien Barati and me during the design process of the Dialogue camera for the diner. The interactive demo for this virtual camera can be found on the companion CD-ROM in the Virtual Cameras folder under Dinner15z.cmo.
Step 1: Diner: Conceptual Design
1. Starting point. When traveling to a new city, one of my greatest pleasures is starting a busy day by sharing an early morning breakfast on the street with the local people. Although the ingredients are almost always the same, there are numerous ways to get a breakfast in the street with endless new surprises. I remember the greasy omelettes from Washington; eggs with mayonnaise from Paris; and, of course, Manhattan Greek diners, which are on top of my list. The busy mood of these early morning breakfasts reminds me of Dores scenes of urban congestion in nineteenth-century London. Edgar Allen Poes fantastic novels describe a typical pedestrian who would spend day and night wondering through his own city, following and eating with crowds wherever they are at any time of the day and the night.
Kienholz created a full-size diner sculpture that was my inspiration for the atmosphere created in the virtual diner. The work of Kienholz is influenced by surrealism, hyperrealism and pop art installations. His sculptures and installations convey the feeling of the atmosphere a scene that goes beyond the representation of people and their activity. His installation is a real diner recreated inside a box that you can experience from the inside and the outside.
2. Description of the project. The scene that takes place inside a diner is visible from multiple viewpoints. This gave me the idea of creating the same kind of interactive experience inside a virtual world. I was interested in designing a virtual camera that can use motion in the diner scene to convey the sense of multiple actions happening at the same time.
The virtual camera can react to peoples voices and sounds inside a room. For example, viewers can interact with the virtual camera by talking or clapping their hands.
3. Project preparation and construction. The goal was to create an installation that would retain the complexity of the atmosphere of a diner. After modeling the diner in LightWave, the 3D model is stripped of unnecessary polygons and large textures to reduce the number of polygons and the file size of textures, and therefore the overall file size of the model. All textures are saved in .jpeg format. In the case of double-sided polygons, the outside face of the polygon is deleted. As a result the inside of the box can be seen from cameras located outside the box, which results in what is called a culling effect. This process gives more flexibility for camera placement and cuts down the number of polygons. Polygon reduction and texture compression help to spare rendering power needed for animated characters. In this case, the final 3D model has 5,000 polygons and only three textures.
The female character is modeled in LightWave. The modeling of the characters head requires more details because the virtual camera will frame the head with close-up shots. Low-resolution modeling techniques are applied to parts of the body that will be filmed from far away. The interruption of the modeling of the body in parts that are covered with clothing helps to reduce the number of polygons even more. The final low-resolution model shows 3,786 polygons, which is acceptable if the viewer is using a 3D acceleration card.
The female and male characters are animated in 3ds Max Character Studio, taking advantage of Character Studios biped. You can find a complete description of animating 3D interactive characters in Jean-Marc Gauthiers book Creating 3D Interactive Actors and Their Worlds, by Morgan Kaufmann Publishing.
Although the 3D models are relatively simple, they are loaded with long animations that increase the file size of the virtual world. For example, a virtual world of the diner with characters is about 2MB. The same virtual world is 20MB when animations are added to the characters. This problem comes from using canned animation. These well keyframed sequences of gestures tend to overload a project looking for speed, flexibility, and responsiveness. Event-driven character animation, covered in Chapter 8, will help you to design character animation without key-framed animations.
4. Interactions with visitors inside the virtual space. This installation explores the possibilities of using several large screens to broadcast the points of view of several interactive virtual cameras inside a scene. The installation is designed for people moving through urban spaces where they are unlikely to stop to use a kiosk with a touch screen, a mouse, or a keyboard. The constraints of urban space limit us to a few input devices involving wireless connections such as PDAs (personal digital assistants), cellular phones or simple invisible sensors such as hidden microphones that can respond to gestures or sound.
This particular installation is using such a microphone as a sensor hidden behind the screen. The audience can guide the virtual camera by clapping their hands, talking, tapping their feet or snapping their fingers. The repetition of the same sound can also trigger different motions for example, one clap sends the camera forward and two claps send the camera backward.
Find more turnkey tutorials that detail all the steps required to build simulations and interactions in by Jean-Marc Gauthier: Focal Press, 2005. 422 pages with illustrations. ISBN 0-240-80622-0 ($49.95). Check back to VFXWorld frequently to read new excerpts.
Jean-Marc Gauthier teaches at New York University in the graduate studies department of Interactive Telecommunications and is the author of Interactive 3D Actors and Their Worlds (Morgan Kaufmann Publishers 2000). He is also a consultant at www.tinkering.net and an award-winning 3D artist.
