Manipulation of CAD surface models with haptics based on shape control functions
Introduction
With traditional two-dimensional (2D) based interfaces, e.g. a mouse, many CAD surface models, such as automobile bodies, industrial products, and ship hulls, are difficult to design and edit due to their 3D nature. Interactively designing a surface is often an inefficient and tedious process. Haptic devices provide a powerful new interface that allows engineers to use their sense of touch to interact with digital models, and modify it by pushing, pulling and dragging its surfaces in a natural 3D environment. They show great promise for use in CAD. A haptic-based CAD system, Virtual DesignWorks, has been developed [12]. It works directly on the native boundary-representation (B-Rep) CAD models. The system provides a haptic-based method for designing CAD models. This paper discusses a technique for the deformation of CAD surface models with haptic interaction based on geometric constraints. The deformation is governed by shape control functions. By using the shape control functions, designers can directly manipulate and deform a selected region of a surface to the desired shape in real-time, and generate complex geometry with simple operations. Fig. 1 shows Virtual DesignWorks in operation.
The remainder of the paper is organized as follows. Section 2 presents a review of the related research in the surface design and haptic fields. Section 3 gives a brief description of the Virtual DesignWorks system. Section 4 discusses the deformation of CAD surface models with haptic interaction based on shape control functions. Section 5 compares haptic-based surface design with traditional CAD operations. Finally, Section 6 conveys our conclusions.
Section snippets
Review of related research
This section is organized as 2.1 The existing surface design method, 2.2 Haptic interface. Section 2.1 reviews research concerning surface design. Section 2.2 describes the current research status of haptics.
Overview of Virtual DesignWorks
Recent work on haptic for CAD has led to the development of Virtual DesignWorks, which integrates haptics with CAD [12]. Virtual DesignWorks is a CAD system with dual model representations. It maintains two independent models: a native CAD model (B-Rep) and a haptic geometry model. The two models exist in two relatively independent subsystems or programs. The CAD model in Virtual DesignWorks is the kernel CAD model used in many commercial CAD systems, such as SolidWorks and Unigraphics, etc.
Haptic-based surface manipulation
Virtual DesignWorks combines physically and geometrically based surface manipulation with haptics. From a designer's perspective, the haptic-based deforming operations are similar for both these methods: a designer touches a surface, clicks the haptic button down, pulls, pushes, and drags the surface, and then releases the haptic button. During the operation, the system updates the graphics of the deformed surface in real-time using the method discussed in Section 3.1. The deformed surface will
A comparison of haptic-based surface design with traditional CAD operations
Our assessment of the haptic interface is that, for some CAD operations that are easily expressed in terms of regular shape/feature operations, a haptic interface is not the right interface for the task. However, for some CAD operations, such as free-form based surface operations, haptics does provide a powerful new tool for the design and manipulation of CAD surface models as predicted by the CAD/CAM industry. As discussed in Section 2, with traditional 2D interfaces, interactively designing
Conclusion
With the haptic-based deforming approach, designers can use a haptic interface to directly touch a native B-rep CAD model, and deform it in real-time by simply pushing, pulling and dragging its surfaces. It gives designers greater flexibility for the manipulation of complex CAD surfaces. By using the shape functions, designers can specify the area of deformation, and also have greater controls on the shape of deformation. The technique is numerically efficient, and can deform complex surface
Xiaodong Liu is currently a PhD candidate at Virtual Engineering Center, Queen's University Belfast. He has more than 8 years of industrial experience in the CAD/CAM fields before joining the Virtual Engineering Center. He has served as a session chair/co-chair at several international conferences, e.g. CAD04 and ASME DETC/CIE 2004. His current research interests include geometric modeling, deformable modeling, haptics for CAD, and NURBS.
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2010, CAD Computer Aided DesignCitation Excerpt :Recently, a number of investigations have been proposed to integrate other human–computer interactions into the CAD modeling environments. For instance, Liu et al. [4,5] proposed to use haptic devices to aid surface and solid modeling in their virtual DesignWorks system; designers can use a haptic interface to touch a B-rep CAD model for direct surface manipulations [5]. Diniz and Branco [6] proposed a direct freehand drawing system, which tracks the movement of two LED lights attached to the designer’s hands.
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Xiaodong Liu is currently a PhD candidate at Virtual Engineering Center, Queen's University Belfast. He has more than 8 years of industrial experience in the CAD/CAM fields before joining the Virtual Engineering Center. He has served as a session chair/co-chair at several international conferences, e.g. CAD04 and ASME DETC/CIE 2004. His current research interests include geometric modeling, deformable modeling, haptics for CAD, and NURBS.
Gordon Dodds is a Senior Lecturer and Member of the Steering Group of the Virtual Engineering Center at Queen's University Belfast. His interests include multi-modal virtual reality, image processing, visualisation, sensor fusion, ergonomics and robotic systems. His recent work has involved the combination of CAD and sensed data in a combined representation of artefacts. He is an editor of IFAC Control Engineering Practice and a committee member of the IEEE Robotics and Automation and Intelligent Robots and Systems conferences. He received his PhD and BSc degrees in Electrical and Electronics Engineering from Queens University Belfast. He is a Senior Member of the IEEE. He is presently Chair of the United Kingdom and Republic of Ireland Section of the IEEE.
Jim McCartney holds the post of senior lecturer in the School of Mechanical and Manufacturing Engineering at the Queens University Belfast. He has considerable experience in the development of 3D CAD systems for clothing and shoes. In particular he is interested in the processes of flattening 3D surfaces into 2D patterns and the reverse process of draping 2D patterns onto 3D templates. He has been involved in many government and industrial funded projects that have investigated these areas of research and is currently concentrating on the performance of materials during flattening and draping.
Brendan Hinds is currently a senior lecturer in the School of Mechanical and Manufacturing Engineering at the Queens University Belfast. His academic interests include the modeling of fabric deformation, production process modeling, haptic modeling within the computer-aided design environment. He has participated in several collaborative research projects investigating the use of fabric drape modeling as a means of determining the fit and appearance of garments.