Crossroads The ACM Magazine for Students

Sign In

Association for Computing Machinery

Magazine: May 1997 | Volume 3, No. 4

A human's eye view

Frameless Rendering (FR) is a rendering paradigm which performs stochastic temporal filtering by updating pixels in a random order, based on most recent available input data, and displaying them to the screen immediately [1]. This is a departure from frame-based approaches commonly experienced in interactive graphics. A typical interactive graphics session uses a single input state to compute an entire frame. This constrains the state to be known at the time the first pixel's value is computed. Frameless Rendering samples inputs many times during the interval which begins at the start of the first pixel's computation and ends with the last pixel's computation. Thus, Frameless Rendering performs temporal supersampling - it uses more samples over time. This results in an approximation to motion blur, both theoretically and perceptually.This paper explores this motion blur and its relationship to: camera open shutter time, current computer graphics motion-blur implementations, temporally anti-aliased images, and the Human Visual System's (HVS) motion smear quality (see 'quality' footnote) [2].Finally, we integrate existing research results to conjecture how Frameless Rendering can use knowledge of the Human Visual System's blurred retinal image to direct spatiotemporal sampling. In other words, we suggest importance sampling (see 'sampling' footnote) by prioritizing pixels for computation based on their importance to the visual system in discerning what is occurring in an interactive image sequence.

By Ellen J. Scher Zagier

HTML | In the Digital Library
Tags: Computer vision problems, Design, Human computer interaction (HCI), Measurement, Motion capture, Motion processing, Performance, Scene understanding, Theory, Video segmentation

Levels of detail & polygonal simplification

This paper covers the techniques of Polygonal Simplification in order to produce Levels of Detail (LODs). The problem of creating LODs is a complex one: how can simpler versions of a model be created? How can the approximation error be measured? How can the visual degradation be estimated? Can all this be done automatically? After exposing the basic aims and principles of polygonal simplification, we compare recent algorithms and state their various qualities and weaknesses.

By Mike Krus, Patrick Bourdot, Françoise Guisnel, Gullaume Thibault

HTML | In the Digital Library
Tags: Algorithms, Computational geometry, Design, Design and analysis of algorithms, Performance, Randomness, geometry and discrete structures, Shape inference, Shape modeling, Shape representations, Symbolic and algebraic algorithms, Theory

Faster 3D game graphics by not drawing what is not seen

The increasing demands of 3D game realism - in terms of both scene complexity and speed of animation - are placing excessive strain on the current low-level, computationally expensive graphics drawing operations. Despite these routines being highly optimized, specialized, and often being implemented in assembly language or even in hardware, the ever-increasing number of drawing requests for a single frame of animation causes even these systems to become overloaded, degrading the overall performance. To offset these demands and dramatically reduce the load on the graphics subsystem, we present a system that quickly and efficiently finds a large portion of the game world that is not visible to the viewer for each frame of animation, and simply prevents it from being sent to the graphics system. We build this searching mechanism for unseen parts from common and easily implemented graphics algorithms.

By Kenneth E. Hoff

HTML | In the Digital Library
Tags: 3D imaging, Algorithmic game theory and mechanism design, Animation, Computer games, Design, Human Factors, Interactive games, Massively multiplayer online games, Modeling and simulation, Performance, Theory