1. 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

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

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

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

5. 2D sketch3D model SparseDense For quick and easy design of trees, we propose –Sketch-based modeling Our method –Example-based modeling

6. Introduction User Interface –Modeling Process –Demonstration Details Result Discussion

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

8. Demonstration

9. 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

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

11. 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

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

13. 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

14. 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

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

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

17. 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

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

19. Three types of leaf arrangements AlternatingGeminatusWhorled Example-based Leaf Arrangements

20. Geminatus Whorled Alternating Example-based Leaf Arrangements

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

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

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

24. 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

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

26. Photograph Our method (10 min) Comparison to Other Systems

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

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

29. 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

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

31. Thanks contact information –Makoto Okabe (makoto21@ui.is.s.u-tokyo.ac.jp)makoto21@ui.is.s.u-tokyo.ac.jp www for this project –http://www-ui.is.s.u-tokyo.ac.jp/~makoto21http://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