Phong reflection model: Difference between revisions

Revision as of 01:16, 25 August 2015

Revision as of 12:54, 23 November 2015

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{{distinguish|Phong shading}}

The '''Phong reflection model''' (also called '''Phong illumination''' or '''Phong lighting''') is an [[Empirical_modellingEmpirical modelling|empirical model]] of the [[illumination model|local illumination]] of points on a [[surface]]. In [[3D computer graphics]], it is sometimes ambiguously referred to as <!--DO NOT LINK-->"Phong shading"<!--DO NOT LINK-->, in particular if the model is used in combination with the [[Phong shading|interpolation method of the same name]] and in the context of [[pixel shader]]s or other places where a lighting calculation can be referred to as “[[shading]]”.

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The Phong reflection model contains many parameters, such as the surface diffuse reflection parameter ([[albedo]]) which may vary within the object. Thus the normals of an object in a photograph can only be determined, by introducing additional information such as the number of lights, light directions and reflection parameters.

For example, we have a cylindrical object, for instance a finger, and wish to compute the normal <math>N=[N_x, N_z]</math> on a line on the object. We assume only one light, no specular reflection, and uniform known (approximated) reflection parameters. We can then simplify the Phong equation to:

:<math>I_p(x) = C_a + C_d (L(x) \cdot N(x)) </math>