An Efficient Alias-free Shadow Algorithm for Opaque and Transparent Objects

晃晃

An Efficient Alias-free Shadow Algorithm for Opaque and Transparent Objects

using per-triangle Shadow Volumes

Erik Sintorn Ola Olssony Ulf Assarssonz

Chalmers University Of Technology Chalmers University Of Technology

Chalmers University Of Technology







Abstract

This paper presents a novel method for generating pixel-accurate

shadows from point light-sources in real-time. The new method is

able to quickly cull pixels that are not in shadow and to trivially ac-

cept large chunks of pixels thanks mainly to using the whole trian-

gle shadow volume as a primitive, instead of rendering the shadow

quads independently as in the classic Shadow-Volume algorithm.

Our CUDA implementation outperforms z-fail consistently and sur-

passes z-pass at high resolutions, although these latter two are hard-

ware accelerated, while inheriting none of the robustness issues as-

sociated with these methods. Another, perhaps even more impor-

tant property of our algorithm, is that it requires no pre-processing

or identification of silhouette edges and so robustly and efficiently

handles arbitrary triangle soups. In terms of view sample test and

set operations performed, we show that our algorithm can be an or-

der of magnitude more efficient than z-pass when rendering a game-

scene at multi-sampled HD resolutions. We go on to show that

the algorithm can be trivially modified to support textured, semi-

transparent and colored semi-transparent shadow-casters and that

it can be combined with either depth-peeling or stochastic trans-

parency to also support transparent shadow receivers. Compared

to recent alias-free shadow-map algorithms, our method has a very

small memory footprint, does not suffer from load-balancing issues,

and handles omni-directional lights without modification. It is eas-

ily incorporated into any deferred rendering pipeline and combines

many of the strengths of shadow maps and shadow volumes.

CR Categories: I.3.7 [Computer Graphics]: Three-Dimensional

Graphics and Realism—Color, shading, shadowing, and texture;

Keywords: shadows, alias-free, real time, transparency



1 Introduction

Generating accurate shadows from point light-sources for each

pixel sample remains a challenging problem for real-time appli-

cations. Despite generations of research, we have yet to see a

pixel-accurate shadow-algorithm for point lights that requires no

pre-processing, works on any arbitrary set of triangles and that***ns

at stable real-time frame rates for typical game-scenes on consumer

level hardware. Traditional shadow mapping [Williams 1978] tech-

niques generate shadows from a discretized image representation

of the scene and so alias when queried for light visibility in screen

space. Real-time techniques based on irregular rasterization [Sin-

torn et al. 2008] tend to generate unbalanced workloads that fit cur-

rent GPUs poorly and consequently, frame rates are often very un-

stable. Real-time ray tracing algorithms rely heavily on geometry

pre-processing to generate efficient acceleration s***ctures. Finally,

robust implementations of the Shadow-Volume algorithm require

pre-processing the mesh to find edge connectivity, work poorly or

not at all for polygon soups without connectivity, and have frame

rates that are all but stable as the view of a complex scene changes.

Nevertheless, the idea of directly rasterizing the volumes that rep-

resent shadows onto the view samples remains compelling. In the

upcoming sections, we hope to convince the reader that this basic

idea is sound and that choosing the right manner of rasterization is

the key to efficiently generate shadows using shadow volumes.









全文请下载附件：

tc

加精、加亮滴铁子，尤其要多丁页丁页

C.R.CAN

既来之，则看之！

奇

提醒猪猪，千万不能让你看见

奇

有意思！学习了！

C.R.CAN

路过、路过、快到鸟，列位请继续...ing

菜刀吻电线

跑着去顶朋友滴铁

tc

路过、路过、快到鸟，列位请继续...ing