A COMPUTER-GRAPHICS BASED MODEL FOR SCATTERING FROM OBJECTS OF ARBITRARY SHAPES IN THE OPTICAL-REGION

A general computer graphics based model, named DIANA, is presented for computer generation of objects of arbitrary shape (including vegetation canopies) and for calculating bidirectional reflectances and scattering from them, in the visible and near infrared regions. The computer generation uses a modified Lindenmayer system (L-system) approach. With this approach, one can, in a simple way, generate objects of arbitrary shapes (such as plants and trees and their canopies, houses of various shapes, and mountains) as well as simulation of their growth, dynamics, and movement. In rendering an object on a computer screen, the object is divided into facets (triangles and quadrilaterals), and some existing and some new computer graphics techniques are used to display the object, with shading and shadowing appropriately taken into account. These rendering techniques are also used, in an innovative way, to calculate the scattering and reflectance from the object. The use of the technique is illustrated with scattering from canopies of simulated corn plants. The scattering is quantified using traditional measures like bidirectional reflectance factor and albedo as well as rendering of the canopies with brightness of a facet proportional to the amount of light scattered from the object in the viewer's direction.