C.P. Verbeck, D. Greenberg. A Comprehensive Light-Source Description for Computer Graphics. IEEE CG&A, 4(7):66-- 75, July 1984. 1 c # The Eurographics Association 2003.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....6. 2 A SURVEY OF LIGHT SOURCES AND THEIR REPRESENTATION In this section, we will first describe the characteristics of light sources commonly used in computer graphics. Then, several means to represent the emission of a light source will be presented. 2. 1 Light Sources Characteristics In [VG84], Verbeck and Greenberg described light sources as a combination of three parameters: the geometry of the light source, its luminous intensity distribution and its emitted spectral distribution. 2.1.1 Geometry The shape of a light source may vary widely: let s think to the area of sky seen ....

C. P. Verbeck and D. P. Greenberg. A Comprehensive Light Source Description for Computer Graphics. IEEE Computer Graphics and Applications, 4(7):66--75, 1984.

....at every scan line. The authors recently presented a modi cation of Lane s method which subdivides surfaces not into polygons, but into subpatches with curved boundaries, which makes for better precision (Nishita 1991) Next we will outline previous models of linear and nite area light sources. Verbeck and Greenberg(1984) simulated linear and area sources by multiple point sources. However, the method causes aliasing artifacts and results in uneven intensity in the shadow area due to the simulation of a continuous light source as a set of discontinuous point sources. The authors of the current paper derived ....

Verbeck, C.P., Greenberg, D.P.(1984) A Comprehensive Light Source Description for Computer Graphics. IEEE CG & A, Vol. 4, No. 7, pp. 66-75.

.... of the geometry, though often treated separately, is the light source (or luminaire) In more recent work, light sources are becoming increasingly complex, with non isotropic emission characteristics, varied geometries and high spectral variation (required for the treatment of flourescent sources) [VG84, LT92]. 1.2 Surface Data The characteristics of each surface in terms of how that surface is perceived under various lighting conditions depends entirely on the manner in which the surface scatters incident light radiation. The selective absorption of light wavelengths gives rise to the colour of the ....

C. P. Verbeck and D. P. Greenberg. A comprehensive light-source description for computer graphics. IEEE Computer Graphics and Applications, 4(7):66--75, 1984.

....sources with a diffuse spatial energy distribution and point light sources with a non uniform spatial energy distribution. However, this does not deal with extended light sources. In order to take into account extended light sources, other models based upon gonio photometric diagrams were designed [4, 5, 9]. However these kinds of models cannot take into account precisely the effect of an extended light source on a given scene, as the area of usage of gonio photometric curves (i.e. the distance between the light source and the surfaces of the scene) must be restricted around a certain distance. ....

....results, it does not treat extended light sources. A method for modeling extended light sources may involve meshing the surface of the light sources and, under certain hypotheses, approximating the equation 1 by a simple sum over the set of patches, as in the solution proposed by Verbeck et al. [5], Tellier et al. 4] Poulin et al. 9] These methods suppose the spatial energy distribution is constant over the surface of the light source and therefore constant for each patch of the surfaces. This allows us to write : L (x) X i ae (x)cos xin S i I (x s i ; out i ; OE out i ) ....

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C. P. Verbeck and D. P. Greenberg. A comprehensive light-source description for computer graphics. IEEE CG&A, pages 66--75, July 1984.

....x s in direction xs out , H(x s ; x) the visibility function between x s and x, xin : the direction given by x and x s , xs : the angle between the source s normal and xs out . Methods for modeling the spatial energy distribution of non point light sources have been proposed in [NON85, LT92, VG84, PA90, TT91, Pic92]. Recall that, given the spatial distribution of every point of a light source, the problem is to compute the behaviour of a surface lighted by this source by using an approximation of the equation (1) In fact this kind of method uses the data given by photometry laboratories which consider light ....

C. P. Verbeck and D. P. Greenberg. A comprehensive light-source description for computer graphics. IEEE CG&A, pages 66--75, July 1984.

.... far field photometry cannot accurately predict luminances when indirect luminaires are mounted close to the ceiling, the luminaires can be modeled as equivalent point sources (i.e. application distance photometry see Stannard and Brass [1990] or homogeneous arrays of point sources (e.g. Verbeck and Greenberg [1984]) Ceiling illuminance and luminance distribution predictions can then be made using finite element radiative transfer calculations (e.g. Mistrick and DiLaura [1987] While the predictions may not always be accurate (Mistrick and English [1990] they are nevertheless usually sufficient for ....

Verbeck, C.P. and D.P. Greenberg [1984]. "A Comprehensive Light-Source Description for Computer Graphics", IEEE Computer Graphics and Applications 4:7, 66 - 75.

....defined in terms of moments, the procedures given in the previous section may be used to simulate directional luminaires, glossy reflections, and glossy transmissions. 6. 1 Directional Luminaires Methods for simulating the illumination due to di#use area sources [12] and directional point sources [23] are well known; however, directional area sources are problematic for deterministic algorithms. In this section we shall see how a class of directional luminaires can be handled using double axis moments. Let P be a polygonal luminaire whose emission distribution is spatially uniform but varies ....

Verbeck, C. P., and Greenberg, D. P. A comprehensive light-source description for computer graphics. IEEE Computer Graphics and Applications 4, 7 (July 1984), 66--75.

....these environments. However, this is not the case. Most rendering systems rely on isotropic point sources with light direction controls (Warn 1983) or line and area (i.e. extended) sources modeled by discrete spatial arrays of point sources (Hall and Greenberg 1983, Brotman and Badler 1984, Verbeck 1984, Verbeck and Greenberg 1984, Houle 1991, and Houle and Fiume 1993) At best, a few systems model extended area sources as homogeneous one and twodimensional continua (Nishita et al. 1985, Tanaka and Takahashi 1991, Poulin and Amanatides 1990, Picott 1992, and Nishita et al. 1992) Verbeck and ....

....However, this is not the case. Most rendering systems rely on isotropic point sources with light direction controls (Warn 1983) or line and area (i.e. extended) sources modeled by discrete spatial arrays of point sources (Hall and Greenberg 1983, Brotman and Badler 1984, Verbeck 1984, Verbeck and Greenberg 1984, Houle 1991, and Houle and Fiume 1993) At best, a few systems model extended area sources as homogeneous one and twodimensional continua (Nishita et al. 1985, Tanaka and Takahashi 1991, Poulin and Amanatides 1990, Picott 1992, and Nishita et al. 1992) Verbeck and Greenberg (1984) noted that ....

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Verbeck, C. P. and D. P. Greenberg. 1984. "A Comprehensive Light-Source Description for Computer Graphics," IEEE Computer Graphics and Applications 4(7):66-75.

....these environments. However, this is not the case. Most rendering systems rely on isotropic point sources with light direction controls (Warn 1983) or line and area (i.e. extended) sources modeled by discrete spatial arrays of point sources (Hall and Greenberg 1983, Brotman and Badler 1984, Verbeck 1984, Verbeck and Greenberg 1984, Houle 1991, and Houle and Fiume 1993) At best, a few systems model extended area sources as homogeneous one and twodimensional continua (Nishita et al. 1985, Tanaka and Takahashi 1991, Poulin and Amanatides 1990, Picott 1992, and Nishita et al. 1992) Verbeck and ....

Verbeck, C. P. 1984. A Comprehensive Light Source Description for Computer Graphics. M.Sc.

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C.P. Verbeck, D. Greenberg. A Comprehensive Light-Source Description for Computer Graphics. IEEE CG&A, 4(7):66-- 75, July 1984. 1 c # The Eurographics Association 2003.

No context found.

C. P. Verbeck and D. P. Greenberg. A comprehensive light source description for computer graphics. IEEE Computer Graphics & Applications, 4(7):66--75, July 1984.

No context found.

C.P. Verbeck, D. Greenberg. A Comprehensive Light-Source Description for Computer Graphics. IEEE CG&A, 4(7):66-- 75, July 1984. 1 c # The Eurographics Association 2003.

No context found.

C.P. Verbeck, D. Greenberg. A Comprehensive Light-Source Description for Computer Graphics. IEEE CG&A, 4(7):66-- 75, July 1984. 1 c # The Eurographics Association 2003.

No context found.

C. P. Verbeck and D. P. Greenberg. A comprehensive light source description for computer graphics. IEEE Computer Graphics & Applications, 4(7):66--75, July 1984.

No context found.

C. P. Verbeck & D. P. Greenberg, A Comprehensive Light-Source Description for Computer Graphics, IEEE Computer Graphics and Applications, pp 66-75, 1984.

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C. P. Verbeck and D. P. Greenberg. A comprehensive light-source description for computer graphics. IEEE Computer Graphics and Applications, 4(7):6675, July 1984.

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C. Verbeck and D. Greenberg, "A Comprehensive Light-Source Description for Computer Graphics", IEEE Computer Graphics and Applications, Vol. 4, July 1984, pp. 66-75.

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C. Verbeck and D. Greenberg, "A Comprehensive Light-Source Description for Computer Graphics", IEEE Computer Graphics and Applications, Vol. 4, July 1984, pp. 66-75.

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