Reflections such as glint are only seen over a small angular range around the Bi-directional Reflectance Difference Function (BRDF) specular lobe. When modelling a target for input to detection codes it is essential that these types of reflection are modelled accurately as they can have a significant impact on detection range. This paper investigates the use of CameoSim to model the glint effects from 3-D curved shapes in the 3-5µm band. Methods investigated to increase accuracy are: increasing the number of facets, using vertex averaging and the use of true geometry to successfully model IR glint effects. Conclusions are drawn as to the way forward for high fidelity modelling.
The spatial and spectral characteristics of targets and backgrounds must be known and understood for a wide variety of reasons such as: synthetic scene simulation and validation; target description for modelling; in- service target material characterisation and background variability assessment. Without this information it will be impossible to design effective camouflage systems and to maximise the capabilities of new sensors. Laboratory measurements of background materials are insufficient to provide the data required. A series of trials are being undertaken in the UK to quantify both diurnal and seasonal changes of a terrain background, as well as the statistical variability within a scene. These trials are part of a collaborative effort between the Defence Evaluation and Research Agency (UK), Defence Clothing and Textile Agency (UK) and the T.A.C.O.M. (USA). Data are being gathered at a single site consisting primarily of south facing mixed coniferous and deciduous woodland, but also containing uncultivated grassland and tracks. Ideally each point in the scene needs to be characterized at all relevant wavelengths but his is unrealistic. In addition there are a number of important environmental variables that are required. The goal of the measurement programme is to acquire data across the spectrum from 0.4 - 14 microns. Sensors used to include visible band imaging spectroradiometers, telespectroradiometers (visual, NIR, SWIR and LWIR), calibrate colour cameras, broad band SWIR and LWIR imagers and contact reflectance measurement equipment. Targets consist of painted panels with known material properties and a wheeled vehicle, which is in some cases covered with camouflage netting. Measurements have bene made of the background with and without the man- made objects present. This paper will review the results to date and present an analysis of the spectral characteristics fo different surfaces. In addition some consideration will be given to the implications of the data obtained for camouflage design.