tailieunhanh - Wave Propagation 2011 Part 5

Tham khảo tài liệu 'wave propagation 2011 part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Accelerating Radio Wave Propagation Algorithms by Implementation on Graphics Hardware 109 5. Algorithm The input for our algorithms is a database of building structures as described in Section 4. In general the output is a discrete two-dimensional raster image which serves as a role model for the discrete representation of results from GPU computations. An image consists of pixels that are organized in a regular array. Pixels are the data elements of this structure. However pixels are not restricted to contain only color information. Pixel data is interpreted according to the current context of the GPU computation. In order to provide a formal description of the presented algorithms we introduce the following notation see Table 1 Let s x y z be a radiation source location . the transmitter antenna where the height is referred to as . All height values are relative to ground. A wall w of a building structure consists of two points p0 and P1 at ground level and two points p2 and p3 at rooftop level. The set containing all walls w is denoted by W. Additionally we associate a normal vector n with each wall. Normal vectors are perpendicular to their wall and point away from the corresponding building. Since the terrain is assumed to be rather flat and the receiver points are typically located meter above ground we define a receiver plane R to be a discrete set of receiver points at constant height . We restrict ray path calculations to only those paths that intersects the receiver plane. In the following we will describe algorithms which are explicitly designed to run directly on graphics hardware. First we present a method for determining line-of-sight regions. Then we will show how this algorithm can be extended to provide additional non-line-of-sight information. Furthermore we show how the graphics card can be exploited for ray path calculation due to diffraction into street canyons and diffraction over rooftops. GPU implementations are obtained by .