**Specular Reflection and the Phong Model.**

Specular Reflection is the important topic of the Computer Graphics. Moreover, It is the Important subject of the Computer Science & Technological field.

When we look at an illuminated shiny surface, such as polished metal we see a highlight, or bright spot, at certain viewing directions. Moreover, This phenomenon is called **specular reflections, **is the result of the total, or near total reflection of the incident light in a concentrated region around the **specular reflection angle.**

- Moreover, The figure shows specular reflections direction at a point on the illuminated surface. The specular reflection angle equals the angle of the incident light.
- Here we use R as a unit vector in direction of reflection L is unit vector point towards light vector N is unit normal vector and V is the unit vector in viewing direction.
- Also, Objects other than ideal reflectors exhibits specular reflections over a finite range of viewing positions around vector R. Shiny surface have a narrow specular reflection range and dull surface have wide specular reflection range.
**By Phong, specular reflection model**or simply**Phong model**sets the intensity of specular reflections proportional to đđđ^{đđ }â . The angle varies in between 0^{0}to 90^{0}.- Also, Values assigned to
**specular reflections parameter**ns determined by the type of surface that we want to display. A shiny surface assigned ns values large nearly 100 and dull surface assigned small nearly 1. - The intensity of specular reflections depends on the material properties of the surface and the angle of incidence as well as
**specular reflection coefficient,**(đ˝)**for each surface.** -
##### The specular reflections is given by đźđ đđđ = đ¤(đ)đźđđđđ đđ â

- Where đź
_{đ}Â the intensity of light source and is an angle between viewing direction V and specular reflection direction R. - Since the angle between two unit vector V and R we can put đđđ â = đ â đ .
- Also, And also for many surfaces (đ) is constant so we take specular reflection constant as K
_{s}so the equation becomes: - đźđ đđđ = đžđ đźđ(đ â đ )đđ
- Vector r calculated in terms of vector L and N as shown in figure

- Fig. Calculation of vector R by considering projection onto the direction of the normal vector N.
- đ + đż = (2đ â đż)
- đ = (2đ â đż)â đż
- Moreover, Somewhat simplified Phong model is to calculate between halfway vectors H and use product of H and N instead of V and R.
- Here H calculated as follow: H = (L+V)/ (|L+V|)

**Related Terms**

Computer Graphics, Light Source, Basic Illumination Models, Depth Buffer Method

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