WHEN ARCHITECTS AND ENGINEERS at Walt Disney Imagineering Research and Development started planning Disney\u2019s California Adventure theme park in Anaheim, Calif., they planned to use current incarnations of computer-aided design (CAD) software. Then they thought better of it. "We wanted to implement a technology that reflected the state-of-the-art feeling we were trying to convey," says Ben Schwegler, who, as vice president and chief scientist, oversaw the 4-D CAD portion of the project. "We wanted something special."This was just about two years ago, and with the help of Martin Fischer, associate professor of civil and environmental engineering at Stanford University in Palo Alto, Calif., up the road, Schwegler hatched something special: 4-D CAD, an application that enabled project managers to see blueprints as an interactive movie with the added fourth dimension of real-time scheduling. At a stakeholder meeting last summer, more than 400 were on hand to see a vir-tual bear emerge from virtual rock.The biggest accomplishment was the use of 4-D CAD in the development of California Screamin\u2019?a roller coaster that glides next to a man-made lagoon. Because of the water hazard presented by this lagoon, this part of the planning process was scheduled to take a few days, Schwegler says. With production crunched, however, Disney officials were able to test the coaster over the lagoon in virtual time, watching it perform flawlessly on a computer screen in a matter of minutes. A live test didn\u2019t need to be conducted until a few weeks before the park opened. "Believe it or not, with all the safety requirements, building a roller coaster is a lot more difficult than erecting a skyscraper," says Schwegler.