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.

scholarly journals Multistroke Grouping of Online Freehand Axonometric Sketches for Mechanical Models

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Shouxia Wang ◽  
Shuxia Wang ◽  
Weiping He
Keyword(s):  
Conceptual Design ◽  
User Interfaces ◽  
Recognition System ◽  
Sketch Recognition ◽  
Line Drawings ◽  
Mechanical Models ◽  
Grouping Method

Multistroke drawing occurs frequently in conceptual design sketches; however, it is almost unsupported by the current sketch-based user interfaces. We proposed a sketch recognition system based on the multistroke primitive grouping method. Based on grouping the strokes that lie within the mutual boundaries between adjacent regions, we create line drawings from online freehand axonometric sketches of mechanical models. First, closed regions and their boundary bands of the sketch were extracted. Then, the strokes that cross the boundary bands of two or more closed regions are segmented, and the strokes that lie within the intersection of two adjacent boundary bands are grouped. Finally, grouped strokes are simplified into a new single stroke and then fitted as a geometric primitive; thus, the input sketches are recognized to the line drawings. We developed a prototype of the sketch recognition system to evaluate the proposed method. The results showed that the input sketches are simplified into the accurate line drawings efficiently. The proposed method can be applied to both multistroke overtracing and nonovertracing sketches.

scholarly journals Use of a 3D model to improve the performance of laser-based railway track inspection

2018 ◽  
Vol 233 (3) ◽  
pp. 337-355 ◽  
Author(s):  
Jiaqi Ye ◽  
Edward Stewart ◽  
Clive Roberts
Keyword(s):  
3D Reconstruction ◽  
3D Model ◽  
Surface Defects ◽  
Railway Track ◽  
Sensor Technology ◽  
Prototype System ◽  
Laser Sensor ◽  
Railway Systems ◽  
3D Data Processing ◽  
Inspection Techniques

In recent decades, 3D reconstruction techniques have been applied in an increasing number of areas such as virtual reality, robot navigation, medical imaging and architectural restoration of cultural relics. Most of the inspection techniques used in railway systems are, however, still implemented on a 2D basis. This is particularly true of track inspection due to its linear nature. Benefiting from the development of sensor technology and constantly improving processors, higher quality 3D model reconstructions are becoming possible which push the technology into more challenging areas. One such advancement is the use of 3D perceptual techniques in railway systems. This paper presents a novel 3D perceptual system, based on a low-cost 2D laser sensor, which has been developed for the detection and characterisation of physical surface defects in railway tracks. An innovative prototype system has been developed to capture and correlate the laser scan data; dedicated 3D data processing procedures have then been developed in the form of three specific defect-detection algorithms (depth gradient, face normal and face-normal gradient) which are applied to the 3D model. The system has been tested with rail samples in the laboratory and at the Long Marston Railway Test Track. The 3D models developed represent the external surface of the samples both laterally (2D slices) and longitudinally (3D model), and common surface defects can be detected and represented in 3D. The results demonstrate the feasibility of applying 3D reconstruction-based inspection techniques to railway systems.

Research on Extracting Skeleton of Mechanism

2011 ◽  
Vol 80-81 ◽  
pp. 1268-1272
Author(s):  
Tian Zhong Sui ◽  
Lei Wang ◽  
Pei Chao Jia
Keyword(s):  
Three Dimensional ◽  
Prototype System ◽  
Gear Pair ◽  
Product Model ◽  
Assembly Features ◽  
Digital Mockup ◽  
The Given ◽  
Geometric Primitives

The model of extracting a skeleton of mechanism is established from an existed three-dimensional CAD product model. Using assembly features, a recomposition of assembly information is carried out. At same time, geometric primitives are defined and classified. And according to the information, kinematic pairs are distinguished and matched. Using the given methods, a prototype system extracting and drawing a skeleton of mechanism is developed. Extracting a skeleton of mechanism from digital mockup has been realized primarily, which can deal with rotation pair, sliding pair, gear pair and multi-pair components consisting of these kinematic pairs. Finally, the paper demonstrates the feasibility of extracting a skeleton of mechanism by an application instances.

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