# The illuminated surface appears equally bright from

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The illuminated surface appears equally bright from all viewing directions. What we call the color of an object is the color of the diffuse reflection of the incident light. 7 Diffuse reflection from a surface.
Diffuse Reflection Figure illustrates the illumination with diffuse reflection, using various values of parameter k d between 0 and1. 8 Series of pictures of sphere illuminated by diffuse reflection model only using different k d values (0.4, 0.55, 0.7, 0.85,1.0).
Specular reflection Light sources create highlights, bright spots, called specular reflection . More pronounced on shiny surfaces than on dull. Alpha is shininess coefficient. Higher alpha is narrower. 9 Specular reflection superimposed on diffuse reflection vectors.
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ILLUMINATION MODEL 11
Phong Illumination Model It’s a local illumination model. based on Bui Tuong Phong's informal observation that shiny surfaces have small intense specular highlights, while dull surfaces have large highlights that fall off more gradually. It describes the way a surface reflects light as a combination of the diffuse reflection of rough surfaces with the specular reflection of shiny surfaces along with ambient lighting . 12
Phong Illumination Model Calculate color for arbitrary point on surface Basic inputs are material properties and l, n, v: l = vector to light source n = surface normal v = vector to viewer r = reflection of l at p (determined by l and n) 13
Basic Calculation Calculate each primary color separately

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