Progressive surface modeling scheme from unorganised curves

This paper presents a novel surface modelling scheme to construct a freeform surface progressively from unorganised curves representing the boundary and interior characteristic curves. The approach can construct a base surface model from four ordinary or composite boundary curves and support incremental surface updating from interior characteristic curves, some of which may not be on the final surface. The base surface is first constructed as a regular Coons surface and upon receiving an interior curve sketch, it is then updated. With this progressive modelling scheme, a final surface with multiple sub-surfaces can be obtained from a set of unorganised curves and transferred to commercial surface modelling software for detailed modification. The approach has been tested with examples based on 3D motion sketches; it is capable of dealing with unorganised design curves for surface modelling in conceptual design. Its limitations have been discussed

Incremental simulation modelling for Internet collaborative design

In order to support Web-based collaborative design in terms of transferring or updating models dynamically and efficiently, new incremental modelling and local updating strategies have been developed for simulation modelling application since simulation is more focused on visualisation effects than on geometry details. Based on an assembly connection concept, a drag-and-drop assembly method has also been proposed in simulation assembly. An assembly connection is defined as a group of assembly constraints and it makes assembly easier. A case study example is given to show the content of the proposed research

Novel method of capturing static and dynamic anthropometric data for home design

This paper presents a novel method for capturing and measuring both static and dynamic anthropometric data of people. These data can be then used for barrier-free home design based on a concept of ergonomic design with motion. This new approach utilized a 3D motion capture system as a tool to simultaneously obtain anthropometric information based on body motion analyses. This paper reports the experimental system design, data collection and analysis techniques on body motions

Applying scenarios in user-centred design to develop a sketching interface for human modelling and animation

This paper presents our user and usability studies for applying scenarios in user-centred design to develop a sketching interface for virtual human modelling and animation. In this approach, we utilise the User Centred System Design (UCSD) strategy and spiral lifecycles to ensure system usability and functionalities. A series of usability techniques were employed. After the initial conceptual design, a preliminary user study (including questionnaires and sketching observations) was undertaken to establish the formal interface design. Second, an informal user test was conducted on the first prototype: a “sketch-based 3D stick figure animation interface”. Finally, a formal user evaluation (including performance tests, sketching observations, and interviews) was carried out on the latest version: a “sketch-based virtual human builder”. During this iterative process, various paper-based and electronic-based sketching scenarios were created, which were acted-out by users to help designers evoke and verify design ideas, identify users’ needs, and test the prototype interfaces in real contexts. Benefiting from applying the UCSD strategy and scenario-based design to develop a natural and supportive sketching interface, our investigation can be a useful instantiation for the design of other sketching interfaces where these techniques have not been widely acknowledged and utilised in the past

A sketch-based gesture interface for rough 3D stick figure animation

This paper introduces a novel gesture interface for sketching out rough 3D stick figure animation. This interface can allow users to draw stick figures with the system automatic assistance in figure proportion control. Given a 2D hand-drawn stick figure under a parallel view, there is a challenge to reconstruct a unique 3D pose from a set of candidates. Our system utilizes figure perspective rendering, and introduces the concept of ‘thickness contrast’ as a sketch gesture combined with some other constraints/assumptions for pose recovery. The resulting pose can be further corrected, based on physical constraints of human body. Once obtaining a series of 3D stick figure poses, user can easily sketch out motion paths and timing, and add their preferable sound/background. The resulting 3D animation can be automatically synthesized in VRML. This system has been tested on a variety of input devices: electric whiteboard, tablet PC, as well as a standard mouse

From on-line sketching to 2D and 3D geometry: A fuzzy knowledge based system

The paper describes the development of a fuzzy knowledge based prototype system for conceptual design. This real time system is designed to infer user’s sketching intentions, to segment sketched input and generate corresponding geometric primitives: straight lines, circles, arcs, ellipses, elliptical arcs, and B-spline curves. Topology information (connectivity, unitary constraints and pairwise constraints) is received dynamically from 2D sketched input and primitives. From the 2D topology information, a more accurate 2D geometry can be built up by applying a 2D geometric constraint solver. Subsequently, 3D geometry can be received feature by feature incrementally. Each feature can be recognised by inference knowledge in terms of matching its 2D primitive configurations and connection relationships. The system accepts not only sketched input, working as an automatic design tools, but also accepts user’s interactive input of both 2D primitives and special positional 3D primitives. This makes it easy and friendly to use. The system has been tested with a number of sketched inputs of 2D and 3D geometry

Neural networks based recognition of 3D freeform surface from 2D sketch

In this paper, the Back Propagation (BP) network and Radial Basis Function (RBF) neural network are employed to recognize and reconstruct 3D freeform surface from 2D freehand sketch. Some tests and comparison experiments have been made to evaluate the performance for the reconstruction of freeform surfaces of both networks using simulation data. The experimental results show that both BP and RBF based freeform surface reconstruction methods are feasible; and the RBF network performed better. The RBF average point error between the reconstructed 3D surface data and the desired 3D surface data is less than 0.05 over all our 75 test sample data

A novel updating modelling methodology for free-form surface modifications in the early stages of design

The paper describes the first implementation of a method in which an initial CAD model is updated from a physical model. The method is based on image-mapping in which an initial CAD model is updated from images of a soft rapid prototype model (RPM) which has been sculpted in order to carry out formal developments. The RP model is made by a 3Dimensional-colour printer, has a built-in contrasting grid composed by parallel planes in the X, Y and/or Z co-ordinates and has special consistency allowing it to be easily sculpted with hand modifications. During the sculpting process changes on the surface affect the lines on the RPM, which are the external presence of the internal grid planes and are corresponding to the initial CAD construction lines. These lines (profiles) then are visually contrasted by making use of identical perspective transformations and viewpoints for the virtual model and the RP model image. The initial CAD model is then updated by modifying the surface’s construction lines to match the lines on the RP image by moving control points, such as in the Z direction

A conceptual design tool: Sketch and fuzzy logic based system

A real time sketch and fuzzy logic based prototype system for conceptual design has been developed. This system comprises four phases. In the first one, the system accepts the input of on-line free-hand sketches, and segments them into meaningful parts by using fuzzy knowledge to detect corners and inflection points on the sketched curves. The fuzzy knowledge is applied to capture user’s drawing intention in terms of sketching position, direction, speed and acceleration. During the second phase, each segmented sub-part (curve) can be classified and identified as one of the following 2D primitives: straight lines, circles, circular arcs, ellipses, elliptical arcs or B-spline curves. Then, 2D topology information (connectivity, unitary constraints and pairwise constraints) is extracted dynamically from the identified 2D primitives. From the extracted information, a more accurate 2D geometry can be built up by a 2D geometric constraint solver. The 2D topology and geometry information is then employed to further interpretation of a 3D geometry. The system can not only accept sketched input, but also users’ interactive input of 2D and 3D primitives. This makes it friendly and easier to use, in comparison with ‘sketched input only’, or ‘interactive input only’ systems. Finally, examples are given to illustrate the system

A sketching interface for 3D modeling of polyhedron

We present an intuitive and interactive freehand sketching interface for 3D polyhedrons reconstruction. The interface mimics sketching with pencil on paper and takes freehand sketches as input directly. The sketching environment is natural by allowing sketching with discontinuous, overlapping and multiple strokes. The input sketch is a natural line drawing with hidden lines removed that depicts a 3D object in an isometric view. The line drawing is interpreted by a series of 2D tidy-up processes to produce a vertex-edge graph for 3D reconstruction. A novel reconstruction approach based on three-line-junction analysis and planarity constraint is then used to approximate the 3D geometry and topology of the graph. The reconstructed object can be transformed so that it can be viewed from different viewpoints for interactive design or as immediate feedback to the designers. A new sketch can then be added to the existing 3D object, and reconstructed into 3D by referring to the existing 3D object from the current viewpoint. The incremental modeling enables a 3D object to be reconstructed from multiple sketching sessions from different viewpoints. However, the interface is limited to reconstructing trihedrons from sketches without T-junctions to avoid ambiguity in the hidden topology determination