Walk-Through Illustrations

Frame-Coherent Pen-and-Ink Style

in a Game Engine

Walk-Through Illustrations

Frame-Coherent Pen-and-Ink Style

in a Game EngineBert Freudenberg

Maic Masuch Thomas Strothotte

Institut für Simulation und Graphik

Universität Magdeburg

Walk-Through IllustrationsWalk-Through Illustrations

Overview•Project background

•Games & NPR

•Our pen-and-ink style

•Outlining

•Surfaces

•Future directions

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Excavation in 60ies

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Virtual reconstruction since 1997

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Visualizing uncertainty NPR

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New challenge: Museum exhibition

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Three projectors in spherical room

5.8 m

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Real-time visualization?•Usual answer: Multi-pipe Onyx + Performer

•Big $$$

•Boring

•Our answer: 3 PCs + Game Engine

•Much cheaper

•More fun

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3D Game Engine provides•Efficient 3D content rendering

•Networking for different views

• Interaction

Just need real-time NPR in that engine!

Games & NPRGames & NPR

Pencil Whipped

Games & NPRGames & NPR

NPRQuake

Games & NPRGames & NPR

Why no commercial real-time NPR games?•Must support wide range of hardware

•Processor speed

•Graphics board

•Rather new field

•Probably soon

Pen-and-InkPen-and-Ink

Elements•Outlines

•Silhouettes

•Discontinuities

•Surfaces

•Hatching

•Detail

New idea: 42 = 18 + 16 + 8

Draw? No Yes Maybe

OutlinesOutlines

Modeling edges• sharp or smooth

Preprocess•determine convexity

Draw edge if• sharp, or

• smooth & convex & silhouette

OutlinesOutlines

Determining convexity

convex(e) v · N < 0

OutlinesOutlines

N

v

e

Drawing edges•GL_LINES

•Display list for sharp edges

•Silhouettes immediate

OutlinesOutlines

SurfacesSurfaces

Textures•Nothing else is fast enough

SurfacesSurfaces

Plain texture on a single quad

SurfacesSurfaces

Conventional mipmapping (average filtering)

SurfacesSurfaces

Average-filtering an ink texture

All gray!

SurfacesSurfaces

Solution•Hatch Maps

•Abuse mipmapping

Hatch MapsHatch Maps

Mipmap levels for hatch maps

Mostly b/w!

Hatch MapsHatch Maps

Mipmapping with hatch maps

Hatch MapsHatch Maps

Mipmapping with hatch maps, trilinear

SurfacesSurfaces

Uniform Hatching•Hatch Maps

Detail / Structure• Ink Maps

Ink MapsInk Maps

Idea•Use hand-drawn maps

Problem•How to generate mipmap levels

Ink MapsInk Maps

Average filtering

Ink MapsInk Maps

Average filtering

Ink MapsInk Maps

Minimum filtering

Ink MapsInk Maps

Minimum filtering

Ink MapsInk Maps

Intelligent filtering?

Ink MapsInk Maps

Intelligent filtering?•Vectorize

•Draw each level for constant width

•Select lines to maintain tone and texture in a pleasing way

How?

Ink MapsInk Maps

Intelligent filtering?•Let an artist do it!

Ink MapsInk Maps

Hand drawn

Walk-Through Illustrations Walk-Through Illustrations

What else?•Color + Shading

Walk-Through Illustrations Walk-Through Illustrations

What else?•Hybrid scenes

Walk-Through IllustrationsWalk-Through Illustrations

Results•Extended a game engine for NPR

•Faster silhouettes

•Mipmap-based pen-and-ink textures

•Frame-coherent

•Constant line width

•Constant density

Walk-Through IllustrationsWalk-Through Illustrations

Prototype implementation (2000)

•Actual exhibition looks different

Walk-Through Illustrations Walk-Through Illustrations

Exhibition

Museum of Cultural History, MagdeburgOpen now until 2nd December 2001

Walk-Through Illustrations Walk-Through Illustrations

Future directions•Add shading

•Use colored lines

•LOD

Walk-Through IllustrationsWalk-Through Illustrations

Acknowledgements •Co-Authors

•Maic Masuch, Thomas Strothotte

•Programming, Modelling

•Niklas Röber, Thomas Fuchs

•Museum of Cultural History, Magdeburg

•Sebastian Kreiker, Babette Ludowici