A Very Brief Overview of Non-Photorealistic Rendering Conrad Albrecht-Buehler Graduate Thesis Seminar September 24, 2001

What is Non-Photorealistic Rendering (NPR)? Rendering of an image to mimic media other than a photograph Gooch: provide info not readily apparent in a photo

NPR’s Usefulness New Artistic Tools Can provide more useful information than a photo might Lends attractiveness to visualizations New modes of visualization

NPR Applications Artist Tool Architecture Cinema Games Scientific Visualization Cartography

Types of NPR Image Space Effects Perspective Space Effects Data Mapped Visualization

Image Space Effects Techniques applied to an output image Style “filters” mimic a familiar artistic style by modifying the pixel image Some work has been done in automatic media generation based on an imput image, e.g. watercolor

From Teece

From Curtis et al.

Perspective Space Effects Techniques applied on input models Much work has been done recreating artistic styles using 3D models as subjects Toon Shaders typically highlight silhouettes based on the model Technical and Architectural sketch renderings are created from models as well

From Teece

From Buchanan and Sousa

From Teece

Data Mapped Techniques applied to input data and mapped to variables Cartography Scientific Visualization

From Agrawala and Stolte

From Healey

Implementing NPR techniques Pencil and Paper NPR for gaming Toon rendering in real-time NPR Quake

Pencil and Paper Rendering Simulating the interaction of paper, pencil lead, eraser, and blender based on an observational model

From Buchanan and Sousa

Cartoon Rendering Most cartoon rendering involves heavy, dark outlines and flat shading. Some work has been done in stylized cartoon rendering such as Dr. Suess

From Kawalski

From Sega’s Fur Fighters

Creating that Toon Look The silhouette is the edge between a front and back facing polygon For every front facing polygon XOR in 1 into the F field For every back facing polygon XOR in 1 into the B field

The Vertex Hash Table VertexVFB X X X00 5 x00 From Buchanan and Sousa

The Vertex Hash Table VertexVFB X X X00 5 x00 From Buchanan and Sousa P[1,2,3]

The Vertex Hash Table VertexVFB X X X00 5 x00 From Buchanan and Sousa P[1,3,4]

The Vertex Hash Table VertexVFB X X X00 5 x00 From Buchanan and Sousa P[3,4,5]

The Vertex Hash Table VertexVFB X X X00 5 x00 From Buchanan and Sousa Silhouette={(1,2),(2,3),(3,4),(1,4)} Note: (3,1) would not be drawn

NPR Quake Intercept OpenGL calls so that the rendering style can be implemented independent of the game engine