1The Sketch L-System: Global Control of Tree Modeling Using Free-form StrokesTakashi Ijiri, Shigeru Owada, Takeo IgarashiPublished in 6th International Symposium SmartGraphics 2006Reviewed byAjit Hakke PatilOutline Introduction Related Work L-Systems User Interface Discussion Conclusion Extensions Questions2Introduction The paper proposes a new Tree modeling system based on L-systems. It allows the user to control the overall appearance and the depth of recursion User can model a new tree just by drawing a single strokeRelated Work L-system Defines structure and rewriting rules Plant modeling L-system based L-String for defining structure Sketch-based interface for 3D modeling Sketch, Teddy, flower modeling system.3L-System A formal grammar Constructs fractal structure by applying rewriting rules sequentially Most famously used to model plant development Introduced by a biologist from Hungary , Lindenmayer in 1968L-System4Sketch L-system Manipulation of the generating rule and its parameters Geometry creation by drawing a strokeManipulation of generating rule and parameters5Rules Terminology Top apex – “a” Lateral Apices – “c” Inter-node – “b” Central Axis – User drawn strokeManipulation Parameters A – Length and the orientation about the Central Axis B – Orientation about its own vertical axis C – Width of the node6Geometry Creation A Free-form user drawn strokeCamera/View Rotation: Barrel button + pen move Zoom In/Out: Middle Mouse button + pen/mouse move7Discussion Most current systems don’t allow to specify global structure and local parameter manipulation E.g Typical L-system structures are defined by strings as “F -> F+[F+F-]”where F is the branch and +,- are rotations, they either used random values for parameters or they are fixed valuesDiscussion Contd. Sketch-Lsystem allows for global control by allowing the user to specify the direction and the depth of the growth It also allows for local parameter manipulation8ResultsApplications/User Study Implemented as a digital art tool for handheld devices9Limitations Predefined rules The central axis/user stroke will always lie in a single plane User study missingConclusion A simple, intuitive interface Ability to manipulate while your drawing Could be used a learning tool for understanding use of L-systems for modeling of trees Lot of room for improvement using gesture based interface10Extensions Support for drawing the rules instead of having predefined rules Generic L-system modeling tool; Visualizing other L-system based fractal structures Multi-stroke
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