Interactive Design of Botanical Trees using Freehand Sketches and Example-based Editing

Makoto Okabe1, Shigeru Owada1,2 , Takeo Igarashi1,3

The University of Tokyo1, Sony CSL2,

JST PRESTO3

• 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 sketch 3D model

Sparse Dense

• 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 Hull 3D 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)

mergingmerging

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 yi so that

Resulting 3D Trees

• 2D sketch resulting 3D tree models

• Three types of leaf arrangements

AlternatingGeminatus Whorled

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 nodes 30,000 nodes 4,300 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

Comparison to Other Systems

Photograph L-system ( 60 min ) XFrog ( 30 min )

Photograph Our method (10 min) 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 (makoto21@ui.is.s.u-tokyo.ac.jp)

• www for this project– http://www-ui.is.s.u-tokyo.ac.jp/~makoto21

• Thanks very much– This work was funded in part by the Japanese

Information-Technology Promotion Agency (IPA)– Eurographics reviewers