Interactive Design of Botanical Trees using Freehand Sketches and Example-based Editing Makoto Okabe 1, Shigeru Owada 1,2, Takeo Igarashi 1,3 The University of Tokyo 1, Sony CSL 2, JST PRESTO 3

Introduction –Motivation –Previous Work –Our method User Interface Details Result Discussion

Motivation 3D trees are important in –Cityscape design –Virtual reality –Consumer games 3D tree modeling is difficult –Enormous structural complexity

Previous Work Rule-based approaches –L-systems –Xfrog –SpeedTree Difficult for novices 3D tree libraries –Maya - Paint Effects Difficult to design an arbitrary tree

2D sketch3D model SparseDense For quick and easy design of trees, we propose –Sketch-based modeling Our method –Example-based modeling

Introduction User Interface –Modeling Process –Demonstration Details Result Discussion

Modeling Process (a) 2D Sketch (b) 3D Construction(c) Multiplication (e) Propagation(d) Leaf-arrangement

Demonstration

Introduction User Interface Details –Creating a 3D Tree from a 2D Sketch –Extension of the Basic Algorithm –Creating a Branch with Spiral Structure –Example-based Leaf Arrangements Result Discussion

Creating a 3D Tree from a 2D Sketch Decide depths of branches Keep the appearance from the view point Resulting shape has infinite possibility

Creating a 3D Tree from a 2D Sketch Observation of natural trees –A natural tree spreads their branches to absorb sun light as efficiently as possible –The distances between a branch and other branches tend to be as large as possible

Creating a 3D Tree from a 2D Sketch Decide depths of branches one by one Compute distances between branch shadows Maximize distances among branches

Other constraints –A 3D hull obtained from the 2D convex hull Keep the overall shape of a tree –Length of a branch –Angle between two branches Creating a 3D Tree from a 2D Sketch 2D Convex Hull3D Hull

Extension of the Basic Algorithm Problem of the described algorithm –Front view is kept –Side view is strange side view front view People omit branches spreading backward or forward

Extension of the Basic Algorithm simple ad hoc trick basic algorithm rotated version (by 90 degrees) merging 90 degrees

Extension of the Basic Algorithm The resulting 3D tree –Front and side views look similar front view side view

Creating a Branch with Spiral Structure Decide depth values so that the branch stroke has a constant 3D curvature –[Floral diagrams and inflorescences, Ijiri et al, SIGGRAPH 2005] (a)(b) (c) Calculate y i so that

Resulting 3D Trees 2D sketch  resulting 3D tree models

Three types of leaf arrangements AlternatingGeminatusWhorled Example-based Leaf Arrangements

Geminatus Whorled Alternating Example-based Leaf Arrangements

Introduction User Interface Details Result –Designed by Experts –Designed by Test Users –Comparison to Other Systems Discussion

Designed by Experts (a) young tree(b) zelkova(c) maidenhair 7,900 nodes30,000 nodes4,300 nodes

Designed by Test Users (d) 9 min(e) 6 min(f) 6 min (a) 6 min(b) 8 min(c) 7 min

L-system, Xfrog and our system Recruited 3 novice users (A, B, C) –L-system (A and B together) –Xfrog (C) –Our system (A, B, C individually) Photograph of a target tree Comparison to Other Systems

PhotographL-system ( 60 min )XFrog ( 30 min )

Photograph Our method (10 min) Comparison to Other Systems

Our system –The major branching structures by sketching The other systems –Detailed structures produced by rules Comparison to Other Systems

Introduction User Interface Details Result Discussion –Summary –Limitations and Future Work

Summary We proposed a system for quick and easy design of 3D trees –Creating a 3D Tree from a 2D Sketch –Example-based modeling The user can design a tree intuitively, especially major branching structures –User Tests –cf) Rule-based systems

Limitations and Future Work Incorporating more natural phenomena –e.g.) Tropisms from user-defined branches Construction of forest Editing operations –move, rotate, or bend

Thanks contact information –Makoto Okabe www for this project – Thanks very much –This work was funded in part by the Japanese Information-Technology Promotion Agency (IPA) –Eurographics reviewers