Using%20textures%20to%20simulate%20fur

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Using textures to simulate fur

• Jeff Cousens
• CS 495 Advanced Computer Graphics
• January 31, 2002

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Fur
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Real-Time Fur over Arbitrary Surfaces

• Jerome Lengyel (MSR), Emil Praun (Princeton),
  Adam Finkelstein (Princeton) and Hugues Hoppe
  (MSR)
• I3D 2001 Bi-annual Symposium on Interactive 3D
  Graphics
• Combines several existing texture techniques to
  render interactive fur

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Basis

• Particle Systems
• Reeves in 1983 to simulate fuzzy objects (smoke,
  clouds, fire not fur)
• Volume Textures (texels)
• Kaijya and Kay in 1989 to address non-interactive
  fur

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Basis

• Lapped Textures
• Praun, Finkelstein and Hoppe in 2000 to optimize
  texturing
• Shells
• Lengyel in 2000 to enhance interactive fur

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Limitations of Previous Methods

• Most are computationally intensive
• Interactive methods are limited
• Van Gelder and Wilhelms 1997 rendered a limited
  number of polylines
• Lengyel 2000 requires global parameterization and
  lots of memory
• Silhouettes

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Addressing Limitations

• Shells require parameterization and lots of
  memory
• Lapped textures
• Silhouettes
• Textured fins

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Geometry Preprocessing

• Establish global direction field
• Cover model with lapped textures
• Textures are matched to edges no overlaps
• Seams get lost in textures

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Texture Preprocessing

• Shell textures
• Texture patches to be lapped per geometry
  preprocessing
• Fin textures
• Define a single fin to be used globally

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Runtime

• Surface rendering
• Skin opaque
• Fin rendering
• Silhouette only on edges
• Shell rendering
• Concentric shells surrounding the skin
  semi-opaque

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Lighting

• Banks/Kajiya-Kay model
• HairLighting(u,v)
• KaKd(1-u2)Pd/2Ks(1-v2)Ps/2
• u T L, v T H
• T hair direction per vertex (pre-computed)
• L light direction
• H half-vector between eye and light
• Performed using a lookup table
• Banks self-shadowing approximation

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Other Rendering Concerns

• Visibility
• Level-of-detail
• Overlapped parameterization

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Interactive Hair

• Real-time control of
• Hair color
• Hair length
• Hair direction

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Results

• 5000 faces
• 7500 edges
• 252 patches
• 14 FPS

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Results

• 5000 faces
• 7547 edges
• 306 patches
• 12 FPS

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Results

• Demo

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Future Directions

• One model, multiple hair systems
• Hair features
• Shell multitexturing
• Programmable pixel shaders
• Hair dynamics

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Questions?