Topics in Computer Graphics: Rendering and Color Theory, Study notes of Computer Graphics

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Topics in Rendering

Useful ideas in bitty form to increase your understanding

Non-photorealistic rendering

• pictures don’t need to be a model of reality to be helpful

Multipass rendering

• by performing multiple rendering passes, OpenGL can be persuaded to do
  • some shadows
  • flat mirrors
  • environment maps

Radiosity and global illumination

• light goes from surface to surface as well as from source to surface
• we can model this (with some difficulty)
• doing so leads to beautiful, but expensive, renderings

Non-photorealistic rendering

• Painterly rendering
  • pixels imitate brush strokes

Illustrator like rendering

• silhouettes
• hatches
• stipples

Cartoon by Thomas Nast, from Hertzmann+Zorin

Hatches

• Directions of curvature

Driven by lighting values

Undercuts emphasize dark spots

Hertzmann+Zorin

Basic hatch densities Undercuts emphasize shadows Mach bands give highlights Hertzmann+Zorin

DeCarlo+Santella

Stippling

• Stipple size/density conveys shading

Algorithm:

• Obtain evenly spaced centers by:
• Lloyd’s method
  • choose points at random on plane
  • now:
    • form voronoi diagram
    • move points to cog of voronoi cells
    • iterate
• size/density proportional to average grey level in cell

Secord, from Hertzmann

From Hertzmann