Chapter 4:
Exploiting Temporal Coherence in Walkthrough Rendering

Abstract

In this chapter, we consider accelerated rendering of walkthrough animation sequences using a combination of ray tracing and Image-Based Rendering (IBR) techniques. Our goal is to derive as many pixels as possible using inexpensive IBR techniques without affecting the animation quality. A perception-based spatio-temporal Animation Quality Metric (AQM) is used to automatically guide such a hybrid rendering. The Image Flow (IF) obtained as a by-product of the IBR computation is an integral part of the AQM. The final animation quality is enhanced by an efficient spatio-temporal antialiasing, which utilizes the PF to perform a motion-compensated filtering.

Animations

Scene: ATRIUM

As a first case study for our walkthrough animation we selected an Atrium of the University of Aizu. The considered animation path is shown below.

We marked the location of keyframes and an inbetween frame along the animation path using the following color convention:

• green - the initial keyframes (interval = 25 frames)
• yellow - keyframes for animation segments that we split (interval = 12 or 13 frames)
• cyan - currently selected keyframes
• red - currently derived inbetween frame

IBR & Ray Tracing with motion-compensated filtering QuickTime movie (5MB)

• All keyframes fully ray traced
• Inbetween frames computed using a hybrid of IBR and ray tracing techniques
• Spatial antialiasing: performed
• Temporal antialiasing: performed
• Motion-compensation: performed

IBR & Ray Tracing without any filtering QuickTime movie (7MB)

• All keyframes fully ray traced
• Inbetween frames computed using a hybrid of IBR and ray tracing techniques
• Spatial antialiasing: not performed
• Temporal antialiasing: not performed
• Motion-compensation: not performed

IBR only animation with motion-compensated filtering QuickTime movie (5MB)

• All keyframes fully ray traced
• All inbetween frames computed using IBR techniques
• Spatial antialiasing: performed
• Temporal antialiasing: performed
• Motion-compensation: performed

Scene: ROOM

Ray Tracing with adaptive supersampling QuickTime movie (5MB)

• All frames fully ray traced with adaptive supersampling
• Spatial antialiasing: not performed
• Temporal antialiasing: not performed
• Motion-compensation: not performed

Ray Tracing with adaptive supersampling and perception-based antialiasing QuickTime movie (5MB)

• All frames fully ray traced with adaptive supersampling
• Spatial antialiasing: performed
• Temporal antialiasing: performed
• Motion-compensation: performed

Raw Ray Tracing with perception-based antialiasing QuickTime movie (5MB)

• All frames fully ray traced
• Spatial antialiasing: performed
• Temporal antialiasing: performed
• Motion-compensation: performed

IBR & Ray Tracing with perception-based antialiasing QuickTime movie (5MB)

• All keyframes fully ray traced
• Inbetween frames computed using a hybrid of IBR and ray tracing techniques
• Spatial antialiasing: performed
• Temporal antialiasing: performed
• Motion-compensation: performed