Phong reflection model: Difference between revisions

Revision as of 03:37, 23 June 2020

Revision as of 12:18, 27 December 2020

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When implementing the Phong reflection model, there are a number of methods for approximating the model, rather than implementing the exact formulas, which can speed up the calculation; for example, the [[Blinn–Phong reflection model]] is a modification of the Phong reflection model, which is more efficient if the viewer and the light source are treated to be at infinity.

Another approximation<ref>{{cite web |url=http://dicklyon.com/tech/Graphics/Phong_TR-Lyon.pdf |title=Phong Shading Reformulation for Hardware Renderer Simplification |last1=Lyon |first1=Richard F. |date= August 2, 1993 |publisher= |accessdateaccess-date=7 March 2011}}</ref> that addresses the calculation of the exponentiation in the specular term is the following: Considering that the specular term should be taken into account only if its dot product is positive, it can be approximated as

:<math>\max(0, \hat{R}_m \cdot \hat{V})^\alpha = \max(0, 1-\lambda)^{\beta \gamma} = \left(\max(0,1-\lambda)^\beta\right)^\gamma \approx \max(0, 1 - \beta \lambda)^\gamma </math>