Exploiting Temporal Coherence in Ray Casted Walkthroughs

We present a technique that aims at exploiting temporal coherence of ray casted walkthroughs. Our goal is to reuse ray/object intersections computed in the last frame of the walkthrough for acceleration of ray casting in the current frame. In particular we aim at eliminating the ray traversal and computing only a single ray/object intersection per pixel. If our technique does not succeed in determining visibility, it falls back to the classical ray traversal. Visible point samples from the last frame are reprojected to the current frame. To identify whether these samples can be reused we apply splatting and epipolar geometry constraints. We discuss two additional techniques that handle correct appearance of small objects. We conducted a series of tests on walkthroughs of building interiors. Our method succeeded in determining visibility of more than 78\% of pixels. For these pixels only a single ray/object intersection is executed. The frame rate is increased by up to 47\%. Finally, we argue that the achieved speedup is relatively significant by comparing the performance of our algorithm to the ``ideal'' ray shooting algorithm