IAT 241

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IAT 241

• Jay C. Page
• Class 4

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Rendering

• A computational process which produces a shaded
  projection using
• 3D model(s)
• Materials (shaders) applied to surfaces
• 3D Light Source(s)
• 3D Camera
• Rendering Algorithm

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Rendering Terms

• Z Buffer A 2D array representing distance from
  camera for the polygon filling that pixel
• Z Fighting granularity in the Z-buffer causes
  problems for close overlapping polygons
• Interpolation method of synthesizing data
  between known points

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Rendering Algorithm

• Heavy math (CPU intensive)
• Different algorithms may have special parameters
  for light / material / camera influences
• Maya Software / Maya Hardware / Mental Ray / Maya
  Vector

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Rendering Algorithm

• Maya Hardware - Uses 3D graphics hardware
  capabilities for speed.
• Maya Software - Slower, runs math on CPU.
  Required for some FX
• Mental Ray - Photorealistic renderer, excellent
  shadows and global illumination, etc.

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Rendering Projection

• 3D object is reduced to a 2D projection

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Rendering Evolution

• Wireframe
• Backface removal
• Hidden line removal
• Gouraud Shading
• Phong Shading
• Bump / Displacement Mapping
• Photon mapping
• Normal Mapping

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Hidden Line Removal
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Flat Shading

• Shading determined by face normal

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Gouraud Shading

• Interpolation between vertex normals

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Vertex Normal

• Calculated as the average of the normals of the
  faces which share that vertex.

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Phong Shading

• Normal is calculated per pixel

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Toon Shading

• Flat colours
• Solid Outline

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Bump Mapping

• Normal is calculated per pixel
• Bitmap is used to perturb normal
• Edge outline is not affected

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Displacement Mapping

• Normal is calculated per pixel
• Bitmap is used to perturb normal pixel
  affecting edge outline

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Photon Mapping

• Photons are released into scene
• Photon bounces are mapped per pixel
• Refraction and reflection simulated

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Photon Soup

• 382 Billion photons simulated
• Distributed rendering via background processing

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Normal Mapping

• Bitmap is used to store per pixel vectors

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Material Terms

• Ambient (environmental) colour
• Diffuse (main) colour
• Specular (highlight) colour

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Material Facts

• Materials can be transparent
• Materials can be self illuminating
• Materials can mask special FX
• Materials can use bitmaps to attenuate almost all
  parameters ie transparency
• Materials affect rendering time

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Lighting

• Lights display reflected colour
• Lights mix as additive colour, differently than
  pigment mixing
• Many different ways to calculate shadows
• Lights can have negative intensity
• Lights can be controlled to only affect certain
  object

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Light Mixing
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Scene Lighting

• Contrast displays curves and allows interesting
  shading
• Contrasts can be Value, Hue, or Saturation, also
  combinations of all 3
• Maximum dynamic range should be used over the
  entire scene
• Lighting should fit with scene

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Lighting Online

• 3 Point lighting
• http//www.3drender.com/light/3point.html
• http//www.andrew-whitehurst.net/3point.html
• Natural Lighting
• http//www.itchy-animation.co.uk/tutorials/light01
  .htm
• Light as animation
• http//youtube.com/watch?vAp0771O_eFI
• http//youtube.com/watch?vd5QfmLdw05w
• http//youtube.com/watch?vm6Y8GaRcCOI

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Rendering Links

• http//features.cgsociety.org/story_custom.php?sto
  ry_id1647page1
• http//features.cgsociety.org/story_custom.php?sto
  ry_id1724page1

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End of Slides