scholarly journals What the Back of the Object Looks Like: 3D Reconstruction from Line Drawings without Hidden Lines

2008 ◽  
Vol 30 (3) ◽  
pp. 507-517 ◽  
Author(s):  
Liangliang Cao ◽  
Jianzhuang Liu ◽  
Xiaoou Tang
Keyword(s):  
3D Reconstruction ◽  
Line Drawings

scholarly journals Tolerance Zone-Based Grouping Method for Online Multiple Overtracing Freehand Sketches

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Shuxia Wang ◽  
Shouxia Wang ◽  
Weiping He ◽  
Shengfeng Qin
Keyword(s):  
3D Reconstruction ◽  
Prototype System ◽  
Polygonal Approximation ◽  
Tolerance Zone ◽  
Line Segments ◽  
Line Drawings ◽  
Stroke Group ◽  
Grouping Method ◽  
Screen Space ◽  
Geometric Primitives

Multiple overtracing strokes are common drawing behaviors in freehand sketching; that is, additional strokes are often drawn repeatedly over the existing ones to add more details. This paper proposes a method based on stroke-tolerance zones to group multiple overtraced strokes which are drawn to express a 2D primitive, aiming to convert online freehand sketches into 2D line drawings, which is a base for further 3D reconstruction. Firstly, after the user inputs a new stroke, a tolerance zone around the stroke is constructed by reference to its polygonal approximation points obtained from the stroke preprocessing. Then, the input strokes are divided into stroke groups, each representing a primitive through the stroke grouping process based on the overtraced ratio of two strokes. At last, each stroke group is fitted into one or more 2D geometric primitives including line segments, polylines, ellipses, and arcs. The proposed method groups two strokes together based on their screen-space proximity directly instead of classifying and fitting them firstly, so that it can group strokes of arbitrary shapes. A sketch-recognition prototype system has been implemented to test the effectiveness of the proposed method. The results showed that the proposed method could support online multiple overtracing freehand sketching with no limitation on drawing sequence, but it only deals with strokes with relatively high overtraced ratio.

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