1. How Do Humans Sketch Objects? SIGGRAPH 2012 Mathias Eitz @ Technische Universität Berlin ( 柏林工业 )Technische Universität Berlin James Hays @ Brown UniversityBrown University Marc Alexa @ Technische Universität BerlinTechnische Universität Berlin Speaker: Xiaohua Xie

2. Mathias Eitz M.Eng. degree from Shanghai Jiao Tong UniversityShanghai Jiao Tong University PhD student at Technische Universität BerlinTechnische Universität Berlin Research on sketch: -How Do Humans Sketch Objects? SIGGRAPH 2012 -Sketch-based Shape Retrieval. SIGGRAPH 2012 -Learning to classify human object sketches. ACM SIG. Talks -Photosketcher: interactive sketch-based image synthesis. IEEE CGA -Sketch-based image retrieval: benchmark and bag-of-features descriptors. IEEE TVCG -An evaluation of descriptors for large-scale image retrieval from sketched feature lines. CG ……..

3. #1:A large dataset of human object sketches 20,000 sketches of 250 object categories Using Amazon Mechanical Turk (AMT) - paid “Human Intelligence Tasks (HIT)” to work

4. #2:Human Recognition AMT again Each HIT identifies 4 sketches. Each worker takes no more than 100 HITs. Categories are organized in 3-level hierarchy. Average accuracy: 73.1%. Usually confusions between semantically similar categories (e.g. ‘panda’ and ‘bear’) Easy tasks Difficult tasks

5. #3:Machine Recognition “ Bag-of-word” + ”SIFT” + “soft SVM” works best! Average accuracy: 56%. Extension to semantic sketch-based retrieval and the recognition of artistic sketches. Semantic search Recognizing artistic sketch

6. Some middle conclusions Humans tend to follow a coarse-to-fine drawing strategy: -first outlining with longer strokes and then adding detail. People seem to have more than one iconic (representation) for each category of objects.

7. Conclusions Pay for collecting a sketch dataset. Pay for a study for human recognition on sketches. Study the computer recognition for sketches. Title question: How do humans sketch objects? How? How? How?.....

8. Open questions How to exploit the temporal order of strokes. How could the computer generate distinctive sketches that are immediately recognizable by humans? How universal sketching and sketch recognition is among humans. (different cultures, ages, genders, artistic expertise, etc.)

9. Thank you!!