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Freehand sketch is a natural and intuitive communication channel for idea expression. Lines are drawn one after another to create the outline before additional lines are often drawn over the existing ones to make a sketch clearer. Typically, the sketch is transformed to be a 3D CAD model by a designer for use in subsequent operations. Sketch-based modeling has been researched to support this transformation but mainly for an online sketch on a digital device. For an offline sketch on a paper, commonly found used in practice, sketch-based modeling remains a challenge because a scanned image conceals enriched information on the sketch in a batch of data points. This paper proposes an approach for reconstructing a 3D model from a paper-based overtraced freehand sketch. Two main modules in this approach are single-line drawing identification and 3D reconstruction. The first module where image processing technique is applied is for transforming a paper-based overtraced freehand sketch to be a single-line drawing in order to generate more information about the sketch (i.e., the number of lines and their starting points and endpoints). The second module where progressive reconstruction approach with cubic corner is applied is for reconstructing a 3D model from the obtained single-line drawing. Steps to be taken in both modules have been formalized. The approach has been successfully implemented on LabVIEW, and tested with several samples. [ABSTRACT FROM AUTHOR]

As a simple meaningful external illustration, a group of boundary contours is commonly used for representing the physical appearance of an object of interest on a 2D plane (e.g., a part drawing, CT scan image, a sliced layer, tile pattern). The illustration is understood from the composition of the contours and their attributes that include their shapes, sizes, locations and relationships. Therefore, not only is geometrical information important for contours to be useful in subsequent operations but their topological hierarchy relationships also are essential. Presented in this paper is a topological hierarchy-contour tracing algorithm that is capable of tracing nests of interconnected contours often found in practice and of identifying their topological hierarchy relationships automatically during contour tracing. The algorithm organizes contours by family rather than by group or as individual. However, contours are traced across families generation by generation instead of going deep with one family branch at a time. The outputs of the algorithm are ordered sequences of boundary pixels representing all closed contours and their topological hierarchy relationships. The algorithm has been implemented on LabVIEW, and tested with several samples to illustrate its applications. [ABSTRACT FROM AUTHOR]

Freehand sketching on a paper is commonly found to be used as it is a natural and intuitive communication channel for portraying ideas. Additional strokes are often drawn over the existing ones to make the sketch clearer. For its usefulness in subsequent steps, a sketch is transformed to be a 3D CAD model that is typically performed manually by a designer due to a lack of technology support. Geometrical reconstruction from an offline scanning of a sketch has been a challenge because enriched information obtained during sketching is reduced to a batch of data points. This paper presents an algorithm for identifying a single-line drawing from a paper-based overtraced sketch as it is the first important step towards geometrical reconstruction. Key activities in this approach are thick-line sketch creation, contour boundary extraction, segments identification, and line drawing creation. The algorithm has been successfully implemented on LabVIEW and tested with several samples. [ABSTRACT FROM AUTHOR]

The adaptive crosshatching concept has been introduced for better waste material removal process in Laminated Object Manufacturing. However, the existing approaches that involve a STereoLithography model require additional information from other sources for determining adaptive crosshatch patterns, and for determining the toolpath from intersection points between these customised patterns and cross-sectional contours on their associated layers. Visual representation, on the other hand, seems to be more logical in practice for generating an adaptive crosshatch toolpath. Therefore, the image processing technique has been applied in this research for ease of adaptive crosshatch toolpath generation. For this approach, a uniform crosshatch pattern is created first as a common platform for the entire model. The pattern is modified next for each layer before being mapped onto the layer to determine the toolpath. An algorithm has been developed, and successfully implemented in the LabVIEW program. Some examples are illustrated in this paper to demonstrate the proposed approach. [ABSTRACT FROM AUTHOR]

Boundary contour, a meaningful external representation of area of interest, is widely used in many manufacturing applications (e.g., part machining, rapid prototyping, cutting and packing of irregular shape patterns, and geometrical reconstruction), and appearing on an image, in many cases, are nests of interconnected contours that their information is typically required prior to subsequent manufacturing operations being performed. Presented in this paper is a new contour tracing algorithm for extracting nests of interconnected contours. The algorithm is capable of recognizing junctions between contours sharing common edges and of recommending, among alternatives, a path to proceed to obtain all interconnected contours. Morphological operations have been applied instead of component labeling to achieve the locations of nested contours on an image. The input to the algorithm is a binary image of 1-pixel-wide closed contours, and the outputs are ordered sequences of boundary pixels representing all closed contours. The algorithm has been implemented on LabVIEW, experimented with several contour patterns, and demonstrated its application in manufacturing. [ABSTRACT FROM AUTHOR]