phong Element Reference

Physically-correct modified Phong model for glossy/specular surfaces. More...

Inheritance diagram for phong:

List of all members.

Attributes
clampedSpectrum	kd
	Wavelength-dependent spectrum which scales / attenuates the overall reflectance of the material (diffuse albedo).
clampedSpectrum	ks
	Wavelength-dependent spectrum which scales / attenuates the overall reflectance of the material (specular albedo).
ureal_t	n
	Wavelength-dependent shininess exponent of material; specifies how quickly the Phong lobe falls off from the perfect specular direction which has the effect of changing how "glossy" the resulting surface appears.

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Detailed Description

Physically-correct modified Phong model for glossy/specular surfaces.

The modified Phong model has two inputs: kd, and ks in [0, 1] subject to kd + ks <= 1, where Kd and Ks represent the diffuse and specular reflectivity of the surface respectively (fraction of incoming energy that is reflected diffusely/specularly). A third input, n, represents the specular shininess of the surface, where higher values of n correspond to tighter / sharper specular highlights, and lower values of n correspond to wider / glossier highlights. The Phong bsdf creates a lobe-like distribution with a cos(alpha)^a fallof, where alpha is the angle between an exitant vector and the perfect specular direction and n is the user-specified "shininess" property of the material.

Note:

For more information, please see: E. Lafortune and Y. Willems. Using the modified Phong reflectance model for physically based rendering. Technical Report CW197, Dept of Computer Science, K.U. Leuven, 1994.

phong corresponds to the underlying Milton class 'ModifiedPhongBSDF.'

Visualization of Phong BSDF, with kd=.2, ks=.8, and n=10.

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Attribute Documentation

clampedSpectrum phong::kd

Wavelength-dependent spectrum which scales / attenuates the overall reflectance of the material (diffuse albedo).

type	clampedSpectrum
optional	true
default	0.5
units	unitless

clampedSpectrum phong::ks

Wavelength-dependent spectrum which scales / attenuates the overall reflectance of the material (specular albedo).

type	clampedSpectrum
optional	true
default	0.5
units	unitless

ureal_t phong::n

Wavelength-dependent shininess exponent of material; specifies how quickly the Phong lobe falls off from the perfect specular direction which has the effect of changing how "glossy" the resulting surface appears.

Note:

Higher values of n denote a shinier, more specular surface

type	positive real scalar
optional	true
default	1
units	unitless