Walk-Through Illustrations Frame-Coherent Pen-and-Ink Style in a Game Engine Bert Freudenberg Maic Masuch Thomas Strothotte Institut für Simulation und Graphik Universität Magdeburg

Walk-Through Illustrations Overview Project background Games & NPR Our pen-and-ink style Outlining Surfaces Future directions

Project background Excavation in 60ies

Project background Virtual reconstruction since 1997

Project background Visualizing uncertainty  NPR

Project background New challenge: Museum exhibition

Project background Three projectors in spherical room 5.8 m

Project background Real-time visualization? Usual answer: Multi-pipe Onyx + Performer Big $$$ Boring Our answer: 3 PCs + Game Engine Much cheaper More fun

Project background 3D Game Engine provides Efficient 3D content rendering Networking for different views Interaction Just need real-time NPR in that engine!

Games & NPR Pencil Whipped

Games & NPR NPRQuake

Games & 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-Ink Elements Outlines Silhouettes Discontinuities Surfaces Hatching Detail

New idea: 42 = Draw?NoYesMaybe Outlines

Modeling edges sharp or smooth Preprocess determine convexity Draw edge if sharp, or smooth & convex & silhouette Outlines

Determining convexity convex(e)  v · N < 0 Outlines N v e

Drawing edges GL_LINES Display list for sharp edges Silhouettes immediate Outlines

Surfaces Textures Nothing else is fast enough

Surfaces Plain texture on a single quad

Surfaces Conventional mipmapping (average filtering)

Surfaces Average-filtering an ink texture All gray!

Surfaces Solution Hatch Maps Abuse mipmapping

Hatch Maps Mipmap levels for hatch maps Mostly b/w!

Hatch Maps Mipmapping with hatch maps

Hatch Maps Mipmapping with hatch maps, trilinear

Surfaces Uniform Hatching Hatch Maps Detail / Structure Ink Maps

Idea Use hand-drawn maps Problem How to generate mipmap levels

Ink Maps Average filtering

Ink Maps Average filtering

Ink Maps Minimum filtering

Ink Maps Minimum filtering

Ink Maps Intelligent filtering?

Ink Maps Intelligent filtering? Vectorize Draw each level for constant width Select lines to maintain tone and texture in a pleasing way How?

Ink Maps Intelligent filtering? Let an artist do it!

Ink Maps Hand drawn

Walk-Through Illustrations What else? Color + Shading

Walk-Through Illustrations What else? Hybrid scenes

Walk-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 Illustrations Prototype implementation (2000) Actual exhibition looks different

Walk-Through Illustrations Exhibition Museum of Cultural History, Magdeburg Open now until 2 nd December 2001

Walk-Through Illustrations Future directions Add shading Use colored lines LOD

Walk-Through Illustrations Acknowledgements Co-Authors Maic Masuch, Thomas Strothotte Programming, Modelling Niklas Röber, Thomas Fuchs Museum of Cultural History, Magdeburg Sebastian Kreiker, Babette Ludowici