Low-Complexity Intervisibility in Height Fields
نویسنده
چکیده
Global illumination systems require intervisibility information between pairs of points in a scene. This visibility problem is computationally complex, and current interactive implementations for dynamic scenes are limited to crude approximations or small amounts of geometry. We present a novel algorithm to determine intervisibility from all points of dynamic height fields as visibility horizons in discrete azimuthal directions. The algorithm determines accurate visibility along each azimuthal direction in time linear in the number of output visibility horizons. This is achieved by using a novel visibility structure we call the convex hull tree. The key feature of our algorithm is its ability to incrementally update the convex hull tree such that at each receiver point only the visible parts of the height field are traversed. This results in low time complexity; compared to previous work, we achieve two orders of magnitude reduction in the number of algorithm iterations and a speedup of 2.4 to 41 on 10242 height fields, depending on geometric content.
منابع مشابه
Efficient implementation of low time complexity and pipelined bit-parallel polynomial basis multiplier over binary finite fields
This paper presents two efficient implementations of fast and pipelined bit-parallel polynomial basis multipliers over GF (2m) by irreducible pentanomials and trinomials. The architecture of the first multiplier is based on a parallel and independent computation of powers of the polynomial variable. In the second structure only even powers of the polynomial variable are used. The par...
متن کاملGeographical networks of British hill forts using intervisibility graphs
We present a range of exploratory methods at the intersection of geographical analysis and graph/network theory to investigate placement of Bronze age and Iron age hill forts in a landscape, utilising varying degrees of domain knowledge (expert/archaeologist). Techniques that we employ include: intervisibility/line-of-sight; visible area of hillforts; landcover and geomorphometrics; and network...
متن کاملImage and Intervisibility Coherence in Rendering
Researchers in computer graphics have long regarded the exploitation of image coherence as one of the fundamental opportunities for improving the efficiency of image rendering. We describe in this paper a theoretical and experimental investigation of the potential benefits of exploiting this phenomenon through the use of hybrid rendering strategies that combine area-sampling and pointsampling t...
متن کاملImproving Iranian Intermediate EFL Learners’ Oral Narrative Task Performance in Terms of Accuracy, Fluency and Complexity by Awareness Raising Through Semantic Fields
The effects different awareness-raising techniques might have on language learners’ performance have been studied by many researchers. The present study specifically focused on improving EFL learners’ oral narrative task performance in terms of accuracy, fluency and complexity by awareness raising through semantic fields. The participants in the study included 40 intermediate learners whose ini...
متن کاملScalable Height Field Self-Shadowing
We present a new method suitable for general purpose graphics processing units to render self-shadows on dynamic height fields under dynamic light environments in real-time. Visibility for each point in the height field is determined as the exact horizon for a set of azimuthal directions in time linear in height field size and the number of directions. The surface is shaded using the horizon in...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Comput. Graph. Forum
دوره 31 شماره
صفحات -
تاریخ انتشار 2012