NPR Wrapup Shadows Intro CS 446: RealTime Rendering

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NPR Wrapup Shadows Intro CS 446 Real-Time
Rendering Game Technology

• David Luebke
• University of Virginia

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Demo

• Today Chris Palmer (F.E.A.R.)
• Thursday Jiajun Zhu

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NPR Recap Painterly Rendering

• Impressionistic or painterly rendering
• Sprinkle particles on object surface
• Draw particles as brushstrokes
• Can render images to encode normals, surface
  curvature, depth, color/tone info

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Painterly Rendering
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Other Styles

• Hatching
• Store different cross-hatch patterns representing
  different tones as textures
• Clever ways to use texture hardware to blend
  between tones at run-time
• More info if time permits

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Other Styles

• Graftals are a general term used for strokes,
  decals, little bits of geometry
• Dynamic placement of graftals to achieve certain
  effects/styles

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Other Styles

• Technical Illustration

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Generalizing NPR

• Recent work by researchers in NPR attempts to
  generalize many of these concepts

Coherent Stylized SilhouettesKalnins, Davidson,
Markosian, Finkelstein
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Generalizing NPR

• Recent work by researchers in NPR attempts to
  generalize many of these concepts

Suggestive ContoursDeCarlo, Finkelstein,
Reinkiewicz, Santella
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Gallery of NPR images

• Technical Illustration
• Coherent Stylized Silhouettes
• Suggestive Contours
• SIGGRAPH papers
• NPAR

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Shadows

• An important visual cue, traditionally hard to do
  in real-time rendering
• Outline
• Notation
• Planar shadows
• Soft shadows
• Projective shadows
• Shadow volumes
• Shadow maps
• Shadow optimizations

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Notation

• Light source
• Point vs area
• Occluders receivers
• Identify ahead of time?
• Self-shadowing?
• Shadow
• Umbra
• Penumbra
• Soft vs hard shadows

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Planar Shadows

• Old trick project the occluder geometry to a
  plane and render over ground plane
• Can do with a matrix
• Z-bias issues
• Semiopaque shadows harder
• Stencil and Z-buffer tricks
• Another option generate textured rectangle
• Problems
• Light source inside object (Antishadows)
• Only planar receivers ? no self-shadowing