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
Our method
• For quick and easy design of trees, we propose
– Sketch-based modeling
2D sketch
3D model
– Example-based modeling
Sparse
Dense
• Introduction
• User Interface
– Modeling Process
– Demonstration
• Details
• Result
• Discussion
Modeling Process
(a) 2D Sketch
(b) 3D Construction
(d) Leaf-arrangement
(c) Multiplication
(e) Propagation
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
Creating a 3D Tree from a 2D Sketch
• 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
2D Convex Hull
3D Hull
Extension of the Basic Algorithm
• Problem of the described algorithm
– Front view is kept
– Side view is strange
People omit branches spreading backward or forward
front
view
side
view
Extension of the Basic Algorithm
• simple ad hoc trick
90 degrees
basic
algorithm
rotated version
(by 90 degrees)
merging
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]
Calculate yi so that
(a)
(b)
(c)
Resulting 3D Trees
• 2D sketch  resulting 3D tree models
Example-based Leaf Arrangements
• Three types of leaf arrangements
Geminatus
Alternating
Whorled
Example-based Leaf Arrangements
Whorled
Geminatus
Alternating
•
•
•
•
Introduction
User Interface
Details
Result
– Designed by Experts
– Designed by Test Users
– Comparison to Other Systems
• Discussion
Designed by Experts
(a) young tree
7,900 nodes
(b) zelkova
30,000 nodes
(c) maidenhair
4,300 nodes
Designed by Test Users
(a) 6 min
(b) 8 min
(c) 7 min
(d) 9 min
(e) 6 min
(f) 6 min
Comparison to Other Systems
• 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
Photograph
L-system ( 60 min )
XFrog ( 30 min )
Comparison to Other Systems
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
•
•
•
•
•
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 ([email protected])
• 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