Illumination Models and Surface-Rendering Methods

Shading

Shading Models

• line drawing
• filled wireframes
• flat shading
• smooth shading
• mesh smoothing
• ray tracing
• radiosity lighting model

Calculation of Light

• Ambient Light
• Diffuse Reflection
• Specular Reflections and the Phong Model
• Gamma correction
• Halftone (varying sized dots)
• Dithering

Polygon-rendering methods

• constant-intensity shading (also known as flat shading)
• Gouraud shading (intensity-interpolation scheme)
  • determine the average unit normal vector at each polygon vertex
  • apply illumination model to each vertex and calculate the vertex intensity
  • linearly interpolate the vertex intensity over the surface of the polygon
  • Problem: Mach band
• Phong shading
  • determine the average unit normal vector at each polygon vertex
  • linearly interpolate the vertex normals over the surface of the polygon
  • apply illumination model along each scan line to calculate projected pixel intensities for the the surface points

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  transparencies

  details of shading by John McDonald at DePaul CTI

  Tutoral on Shading from University of California, Davis - Computer Graphics Notes
  some examples from Watt 97
  Large pdf file on rendering Learning Rendering - Alan Watt - University of Sheffield

  The POV-Ray site has nice example images.