3D Animation Streaming 2005

[Martin Hash]

Abstract
In applications where it is imperative that an event occur at a specified time but the data loading requirements cannot be met before the event trigger, like animation distributed over the Internet, it seems appropriate to send the most important data first so that the user at least receives the gist of the information before the application moves on. We offer a framework of graceful degradation of 3D character animation, such that the story narrative is maintained even if data transmission rates are erratic.

Keywords
3D Character Animation, Internet streaming

1. Introduction

Delivering data intended to be displayed as a continuous animation over a constricted transmission channel like the Internet may cause hesitation, which usually degrades the visual narrative. We suggest ways to maintain temporal integrity without perceived loss of information. This is accomplished by predictive preloading the data, and the strategic elimination of low-priority objects. We use heuristics that categorize data by desirability. Algorithmic liturgies then rank objects by importance to determine a precedence list [1].

2. Graceful Degradation

The richness of a 3D rendered scene can be measured by how populated it is and how detailed the objects are. The ideal, of course, is to completely deliver the creator’s intended vision, but if that is not possible due to a technical consideration such as constricted bandwidth, then our goal is to degrade gracefully, which means that the parts of the scene that are eliminated are not important to the viewer’s perception of the story. An example might be two characters conversing in a room that contains furniture and windows to the outside. Gracefully degrading the scene, perhaps the outside scenery could be dropped first, followed by the furniture in the room, and finally the room itself, leaving only the two characters and their dialog to maintain the narrative.

2.1. Precedence

The two values that determine how much of a scene is visible to the viewer are precedence and load time. Precedence can be determined by performing an examination of the data files that describe the animation. Due to the vagaries of Internet transmission, load time can only be roughly estimated by dividing the file size by the predicted data transfer rate. The goal is to minimize the hesitation, or lag, between scenes. There have been extensive studies of how much lag a typical viewer can be expected to tolerate. Viewers become highly critical if the lag reaches a 200-300 ms threshold [2].

Idea05.doc

Published in IDEA05