Reading 17

Citation:

Paulson, Brandon, and Tracy Hammond. "PaleoSketch: accurate primitive sketch recognition and beautification." Proceedings of the 13th international conference on Intelligent user interfaces. ACM, 2008.Publication Link:http://dl.acm.org/citation.cfm?id=1378775

Summary:

This paper aims to recognize low level primitves and then hierarchically construct higher level shapes. As part of pre-recognition this paper has introduced two features: NDDE and DCR. NDDE is calculated as (stroke length between highest and lowest direction points/Total stroke length). DCR is calculated as (maximum change in direction/Average change in direction). NDDE is higher for curves and lower for polylines. This is vice versa for DCR. 

The algorithm determines whether stroke is overtraced or not by computing total number of revolutions the stroke makes diving by 2π. It performs recognition for following shapes:

1) Line

2) Polyline

3) Ellipse

4) Circle

5) Arc

6)Spiral

7) Helix

8) Complex shape

It also assigns hierarchy for all these shapes where it assigns rank for the primitive shapes. Rank of line is 1, arc is 3 and all others have rank of 5. Algorithm suggests the shape with lowest rank.

Discussion:

This paper introduces a lot of threshold values without providing any insight on how they have been derived. The number of threshold values should have been either less, or explained more about. Correct shapes were determined 99.89% of times, which is pretty impressive. Integration with LADDER could have been given more explanation.