A ROBUST MONTE CARLO BASED RAY-TRACING APPROACH FOR THE CALCULATION OF VIEW FACTORS IN ARBITRARY 3D GEOMETRIES

摘要

Drawing on ideas from computer-based graphical representations, the conventional use of finite element based approaches to represent three-dimensional (3D) geometries of interest is challenged in this work by the use of a modest suite of geometric 'primitives' (i.e. generic shapes such as a sphere, a cone, a flat surface) that in combination via a set of affine transformations can provide a realistic approximation to almost any conceivable 3D body. Initially, a robust C~++ program using the latest CPU vectorisation technologies (e.g. OpenMP and Streaming SIMD Extensions) was developed and validated against a broad range (around a dozen) of known analytical view factor solutions. The impact of ray density level, random number generators, and 'fast' numerical approximations for widely used trigonometric functions were all extensively examined at this stage in terms of solution accuracy and required run-time. Extensive use was made at this stage of the in-built program profiling capabilities within the XCode 4.2 IDE to identify 'choke points' within the evolving computer code.