CMSC 635: Advanced Computer Graphics
David S. Ebert
Computer Science and Electrical Engineering Department
University of Maryland, Baltimore County
- ambient -- approximate global illumination effects.
- diffuse -- Lambert's Law -- absorbed and reradiated equally
in all directions (depend on wavelength, independent of observer)
- specular -- reflects off surface => color of light
in many cases is color of object.
- -- rate at which energy is emitted (Watts).
- solid angle
- -- angle at the apex of a cone. It is measured in terms
of the area on a sphere intercepted by a cone whose apex is at the sphere`s
- steradian (sr)
- -- solid angle of a cone that intercepts an area equal
to square of the sphere's radius r.
- hemisphere has
- Radiant intensity
- -- flux per unit solid angle in a given direction.
- -- radiant intensity per unit foreshortened surface area.
- Foreshortened surface area
- - projected surface area -- projection of surface onto
the plane perpendicular to the direction of radiation. It equals to
is the angle between radiation and surface normal.
- -- the incident flux per (unforeshortened) unit surface
Irradiance of incidence light : .
is incident radiance.
Bidirectional reflectivity :
D is distribution function of microfacets orientations
G is geometrical attenuation factor -- masking
and shadowing effects of the microfacet on each other.
is the Fresnel term.
- Phong's model
where m is root mean square slope of microfacets (Beckman distribution).
Shadowing and masking
In another form
Cook-Torrance Illumination (continued)
Also can do it as:
where Red(0) is color of material at normal incidence. Then,
Hall suggested a similar method.
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Last modified: Wed Mar 10 17:07:01 EST 1999