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Advanced Building Simulation

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Graphical<br />

representation<br />

Matrix (4D)<br />

representation<br />

X 000<br />

0 Y<br />

0<br />

0<br />

Z<br />

Motionstar<br />

xyz coordinates<br />

–Y<br />

X<br />

Transformation<br />

Figure 9.19 Transformation from hardware data to programming data.<br />

<strong>Simulation</strong><br />

& graphics<br />

0<br />

0<br />

Z 0<br />

Figure 9.20 Latency due to system lag.<br />

0<br />

0<br />

0<br />

0<br />

Transformation data Sensor<br />

New virtual image<br />

Based on sensor data<br />

Immersive building simulation 233<br />

X 000<br />

0<br />

–Z 00<br />

Y<br />

0<br />

0 Y<br />

0<br />

0<br />

0<br />

0<br />

0<br />

Sun Java3D<br />

xyz coordinates<br />

and process the new view immediately while the computer must generate images with<br />

new sets of transformation matrices from the sensors (Figure 9.20). Most of the<br />

latency issues are tied to the computer system delay (Holloway 1995). Moreover, the<br />

development platform, C�� or Java, is also vital to the processing of such complex<br />

programs (Marner 2002).<br />

Predicting the future viewpoint (and thereby the viewing transformation) could<br />

resolve latency issues. One such predicting algorithm is the “Kalman filter”, which<br />

implements a predictor–corrector type estimator that minimizes the estimated errorcovariance<br />

when some presumed conditions are met. The use of linear accelerometers<br />

and angular rate gyroscopes to sense the rate of motion with the aid of Kalman filter<br />

(Kalman 1960) enables accurate immersive environments such as AR (Chai et al.<br />

1999). Single-Constraint-at-a-Time (SCAAT) tracking integrated with Kalman filtering<br />

has shown improved accuracy and estimates the pose of HiBall tracker in real-time<br />

(Welch et al. 1999).<br />

HMD<br />

Z<br />

View of<br />

real scene<br />

X

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