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Introduction Prev. Work Sys. Design Head-Pose PLoD Tests Conclusions

7.- Discussion

We have presented a real-time system that combines a vision module that estimates the user‘s head pose with a PLOD module that optimizes image rendering based on perceptual parameters. The system was implemented on a fairly modest PC using off the shelf components and it was able to improve the frame rate significantly compared to rendering the same terrain at full resolution. Subject tests were performed to assess the benefits of using uncertainty estimates in conjunction with other parameters. Our results indicated that uncertainty estimates help in making optimizations more seamless to the user. An approach for calculating orientation uncertainty was presented and employed as part of the vision module. However, the jitter in the uncertainty calculations prevented us from achieving the same level of performance compared to using fixed parameters. More details about this work can be found in [23]. Future work includes further investigation of these issues as well as estimating eye-gaze more accurately.

Some recommendations to improve the results of the tracker are using a Gaussian filter on the image before calculating the gradients. A dynamic window size can be implemented to help deal with fast head movement. The optimal value can be computed from the head‘s velocity using previous frames.

The goals were attained but not with 100 percent success. Implementing the recommendations will make the tracker more robust and suitable for its use in the Human Activities Recognition project.

Video

Click here to download a demo video of the system. The green crosshair in the video is the intersection of the head orientation with the screen. The mesh is initially rendered with textures and then as a wireframe to show how the triangles are modified in real time. At the begining the renderring module is not using any optimizations. At 0’44” a static uncertainty measurement is used and one can see that the high resolution region expands. At 0’58” the system is using variable uncertainty and the oscillations become clearly visible.

Acknowledgment

This work was supported by NASA under grant #NCC5-583.

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