Local Illumination

Illumination Model

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ambient light

• $I^{\prime }=K\cdot I$

Diffusion Model (Lambert)

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• $I^{\prime }=K\cdot I\cdot cos\alpha$

Specular Model (Phong)

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• $I^{\prime }=K\cdot I\cdot co{s}^n\theta$
• $\theta :$ reflect-direction ↔ view-direction

Blinn-Phong:

• $I^{\prime }=K\cdot I\cdot co{s}^n\gamma$
• $\gamma :$ halfway-direction ↔ normal-direction

Global Model (Whitted)

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local illumination +

environment specular light +

environment transmission light

• Ray casting Algorithm
• Ray tracing Algorithm
  • Ray tree (recursive)

Shading

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Here comes normal, here comes the same-level color.

• Flat Shading (per face)

  polygon color + polygon normal

  • polygon color
    • calculate polygon color with local illumination using single polygon normal
• Smooth[Gouraud] Shading (per vertex)

  fragment color + vertex normal

  • vertex color
    • calculate vertex color with local illumination using vertex normal
    • *interpolate vertices colors which calculated by local illumination, and give to fragment color*
• Phong Shading (per fragment)

  fragment color + fragment normal

  • vertex normal
    • *interpolate vertices normals, and give to* fragment normal
  • fragment color
    • calculate fragment color with local illumination using fragment normal

Texture Mapping

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• Texture Space $[0,1{]}^2$
  • Geometric texture
    • Bump Mapping
    • Normal Mapping
    • Displacement Mapping
  • Color texture
    • used as color label
    • used as coefficient in light model
• Anti-aliasing
  • Reason: undersampling
  • Solution
    • Prefilter
    • Supersampling
    • Mipmap