Fig. 18

This composite shows four frames from a wrapped cycle of an orbiting virtual camera (at 0°, 90°, 180°, and 270°). The user twirls a poi-like affordance (shown as a knob-terminated segment), which is adaptively projected into the scene. For simplicity, the illustration uses a static actor and affordance position, simple “right pointing,” but typically the manipulable is whirled, even as the virtual camera moves. Each quadrant (delimited by gray rectangles) associates a subject (red, lower) with a projection (blue, upper) through the graphical display (“dot–dash” segment). (“Real” things are shown in blue, “virtual” things in red, and “hybrid” things in purple.) The virtual camera sweeps around (larger, purple oval), changing the perspective on the self-identified avatar (smaller, blue oval). A subtlety lies in the phase adjustment of the affordance’s image: in order to shift continuously between frontal, mirrored (top center) and dorsal, tethered (bottom center) perspectives, displayed azimuth of the object must be perturbed. Although the human actor frozen here in the diagram strikes a static pose across the camera angles, affordance projection is artificially rotated to accommodate the shifting perspective. Environmental lighting surrounding the player, iconified by the “light+camera”s in the figure, represents positions of the virtual camera projected back into user space, the perspective standpoint in the “real” world