NPR (Non-photorealistic Rendering) Billy Davidson CS 395 Advanced Graphics January 22, 2004.

NPR(Non-photorealistic

Rendering)

Billy Davidson

CS 395 Advanced Graphics

January 22, 2004

Non-photorealistic Rendering

Most computer graphics work strives for photorealism

Other types of depiction can be more expressive or artistic

Depict intrinsic or extrinsic properties?

Terminology

Image Picture Intrinsic/Invariant Extrinsic Constancy

Constancy

We do not experience some extrinsic properties of the image we see

3D -> 2D Mappings

Sketches by 7-year old children

Depiction

Depiction is the mapping of properties of the scene to properties of the picture

Traditional 3D -> 2D geometric projection is only one possible meaningful mapping

Projections

Different projections preserve different intrinsic properties

Vision as Inverse Problem

V() = “Visual reaction” function Not invertible due to ambiguity, emotional

factors, etc.

Primary vs. Secondary Space

Respect local rules but not global ones

Primary vs. Secondary Space

Tone mapping

Representation Systems

Spatial system Primitive system Attribute system Mark system

Painterly Rendering

Tarzan

Pen Strokes

Bones

Cel Shading

The Legend of Zelda: The Wind Waker