M. Bass, ed., The Handbook of Optics. McGraw-Hill, second ed., 1995.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....to x is given by #(x # ,x) e # x x # #(#)d# , 2) where #(#) is the extinction coefficient. The phase function f describes how light is scattered within the stone. Since the cracks and air bubbles are larger than the wavelength of light, the type of scattering is described by Mie theory [3]. To simulate the combined effect of back scattering and forwardscattering, we use the two lobed Schlick approximation [4] of the empirical Henyey Greenstein phase function [13] which is a good approximation of Mie scattering. To simulate subsurface scattering in stone, we need to apply a method ....

....estimate [14] This is illustrated in Figure 6. Figure 6 A subsurface scattering event. The interaction of light with the stone surface is simulated with Fresnel s formulae for unpolarized light entering a dielectric medium. This formula is described in most standard texts on optics e.g. [3]. We compute the amount of reflected light at a surface as Fr (x, # #) k ,wherekserves as a simple approximation of surface roughness. As the surface roughness is increased, the surface will become less reflective, in particular for light entering the surface in a direction close to the surface ....

Michael Bass, editor. Handbook of Optics. McGraw-Hill, Inc., New York, NY, 1995.

....the aperture alone moves in a plane that is parallel to the image sensor array, as illustrated in Fig. 1. This aperture motion is also called parallax scanning. 1 The e#ects of an o# center aperture are well known and have been used in passive ranging devices and auto focus lenses [5] 6] [7]. Because of refraction, small displacements of the aperture cause correspondingly small image displacements that depend on 3D object distances. As currently implemented, the aperture travels in a circular path about the nominal optical axis. This causes object points to appear to travel through ....

M. Bass, ed., The Handbook of Optics. McGraw-Hill, second ed., 1995.

....within the medium. A number of different phase functions are available for different types of media. For the materials we consider here, the phase function is not known. One can assume that the sources of scattering (grains, cracks, air bubbles, etc. are larger than the wavelength of light [1] and thus the individual scattering events can be described reasonably well with Mie scattering [11] Instead of simulating each scattering event, we use the empirical Henyey Greenstein phase function [8] to approximate the accumulated effect of Mie scattering. To have control of both back ....

....and forward scattering, we use the two term Henyey Greenstein phase function: f(cos#, g 1 ,g 2 ,w) w 1 g 2 1 (1 2g 1 cos # g 2 1 ) 1.5 (1 w) 1 g 2 2 (1 2g 2 cos # g 2 2 ) 1.5 , 5) where # is the angle between the current direction and the scattered direction. g 1 # [0, 1] controls forward scattering, g 2 # [ 1, 0] controls backward scattering, and w is the weight of the forward scattering lobe relative to the backward scattering lobe. Figure 4 illustrates three configurations of the Henyey Greenstein phase function. 4Results We have implemented the wetness model ....

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Michael Bass (editor), Handbook of Optics, McGraw-Hill, Inc., 1995.

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M. Bass, ed., The Handbook of Optics. McGraw-Hill, second ed., 1995.

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