Hiromasa Suzuki

Making papercraft toys from meshes using strip-based approximate unfolding

We propose a new method for producing unfolded papercraft patterns of rounded toy animal figures from triangulated meshes by means of strip-based approximation. Although in principle a triangulated model can be unfolded simply by retaining as much as possible of its connectivity while checking for intersecting triangles in the unfolded plane, creating a pattern with tens of thousands of triangles is unrealistic. Our approach is to approximate the mesh model by a set of continuous triangle strips with no internal vertices. Initially, we subdivide our mesh into parts corresponding to the features of the model. We segment each part into zonal regions, grouping triangles which are similar topological distances from the part boundary. We generate triangle strips by simplifying the mesh while retaining the borders of the zonal regions and additional cut-lines. The pattern is then created simply by unfolding the set of strips. The distinguishing feature of our method is that we approximate a mesh model by a set of continuous strips, not by other ruled surfaces such as parts of cones or cylinders. Thus, the approximated unfolded pattern can be generated using only mesh operations and a simple unfolding algorithm. Furthermore, a set of strips can be crafted just by bending the paper (without breaking edges) and can represent smooth features of the original mesh models.

Frontal geometry from sketches of engineering objects: is line labelling necessary?

A tool which can quickly interpret line drawings (with hidden lines removed) of engineering objects as boundary representation CAD models would be of significant benefit in the process of engineering design. Inflation of the drawing to produce a frontal geometry, a geometric realisation of that part of the object visible in the drawing, is an important stage of this process. Previous methods of producing frontal geometries have relied on the technique of line labelling (labelling edges as convex, concave or occluding). Although restricted subsets of the line-labelling problem have known solutions, reliable methods have not been found for the general line-labelling problem, and traditional methods, when adapted to drawings with non-trihedral junctions, are unacceptably slow. Many other papers assume that line labelling is an essential step. Here, we show this is not necessarily true, and that comparable results can be obtained by a novel alternative approach. Firstly, we consider what outputs from line labelling are essential to the production of frontal geometry. Secondly, we investigate by what other means these outputs can be produced. Our work indicates that the only essential output from line labelling for frontal geometry is the determination of which T-junctions in a drawing are occluding and which are non-occluding. This information is required for inflation, and also for detection of symmetry and for constructing hidden topology. Thus, we propose and analyse a new method which, in the absence of line labels, simultaneously inflates a drawing to produce the frontal geometry and attempts to determine whether each T-junction is occluding or not. For drawings of objects with holes or pockets, and for cases where line labelling is particularly unreliable, our new method can provide a better alternative.

A two-stage approach for interpreting line drawings of curved objects

We describe a two-stage approach for interpreting line drawings of curved objects. In the first stage, the user enters a natu-ral line drawing of a polyhedral template; this is automatically interpreted as the corresponding polyhedral object. In the second stage, the user enters freehand curves; by relating these to the template, a curved object can be constructed

Computer aided design for Origamic Architecture models with polygonal representation

An Origamic Architecture (OA) is a folded sheet of perforated paper from which a three-dimensional structure pops up when it is opened. It is similar to a pop-up story book, but its unique feature is that it is made purely by cutting a single piece of paper. Because of this limitation, designing an OA requires considerable experience. We propose a computerised method which assists design of OAs. An OA is modelled using a set of planar polygons. This model must satisfy the conditions required of a valid, realisable OA. A unique point of our method is the application of Boolean set operations to the polygons on the unfolded pattern to guarantee that the model can be made from a single sheet of paper. We also present a procedure for checking the models validity. Additionally, we propose methods for creating openings, for generating unfolded patterns, and for displaying folding animation. We have implemented a system based on these methods and demonstrated its usefulness for creating OA. Our system allows designers to intuitively design OA models and to easily generate the unfolded patterns

Can machines interpret line drawings

Engineering design would be easier if a computer could interpret initial concept drawings. We outline an approach for automated interpretation of line drawings of polyhedra, and summarise what is already possible, what developments can be expected in the near future, and which areas remain problematic. We illustrate this with particular reference to our own system, RIBALD, summarising the published state of the art, and discussing recent unpublished improvements to RIBALD. In general, successful interpretation depends on two factors: the number of lines, and whether or not the drawing can be classified as a member of special shape class (e.g. an extrusion or normalon). The state-of-the-art achieves correct interpretation of extrusions of any size and most normalons of 20—30 lines, but drawings of only 10—20 lines can be problematic for unclassified objects.Despite successes, there are caseswhere the desired interpretation is obvious to a human but cannot be determined by currently-available algorithms. We give examples both of our successes and of typical caseswhere human skill cannot be replicated.

Train communication system using graded-index leaky plastic optical fiber

We propose a new train communication system using optical wireless communication. In the proposed system, graded-index (GI) leaky plastic optical fiber (POF) is used as the communication medium. Since this fiber has the structure where scatterers are mixed in the core of normal GI-POF, the light which is entered through the end of this fiber from laser diode (LD) can be leaked along the fiber. This GI leaky POF and a photo detector are installed in train and the ground, and the light which leaks from this fiber is received continuously by a photo detector. From the measurement results, we confirmed that new GI leaky POF has the broadband and low delay characteristics The experimental results show that this new train communication method using a leaky optical fiber is a very promising technology for the future high-speed data communication between trains and a ground.

Attentive Workbench: An Intelligent Production Cell Supporting Human Workers

We propose “Attentive Workbench (AWB),” a new cell production system in which an intelligent system supports human workers. Using cameras, projectors, self-moving trays driven by planar motors and so on, the system recognizes the worker’s condition and intention and supports the workers from both physical and informational aspects. In this paper, AWB is outlined. The control system for multiple self-moving parts trays in AWB is proposed. The results of simulation are shown demonstrating the present control system.

Separated medial surface extraction from CT data of machine parts

This paper describes a new method for extracting separated medial surfaces from CT (Computed Tomography) data of machine parts. Plate structures are common mechanical structures such as car body shells. When designing such structures in CAD (Computer Aided Design) and CAE (Computer Aided Engineering) systems, their shapes are usually represented as surface models associated with their thickness values. In this research we are aiming at extracting medial surface models of a plate structure from its CT data so as to be used in CAD and CAE systems. However, such a structure consist of many components which are adjacent each other. For example, car body shells are consist of many welded plates. CT imaging technology has some weak points in the area. One of them is that, if there are two or more objects made of same material, CT scanner cannot make the distinction between them. The problem is caused by the principles of CT imaging technology. Because CT image represents the mass distribution within a cross section, we cannot separate the objects only from image information. However, there are many requests for scanning assembled parts and separating objects made of same material. Therefore, we propose a method to separate each components. CT data has not enough information amount as has been metinoned, so we adopt other knowledge about model shapes. We conclude with experiments on welded mechine parts for effectiveness of our method.

Three-axis NC cutter path generation for subdivision surface

In this paper we propose methodologies and algorithms of NC cutter path generation for subdivision surfaces. We select Loop surface as the subdivision surface. A path plan including rough cut and finish-cut is developed based on LoD (level of detail) property of the subdivision surface. We generate a coarse mesh that covers the limit surface to implement rough cut. For finish-cut we use ball-end mills and offset cutter contact positions to generate cutter location. In these two steps we use a Z-map model and a collision detection and correction method is presented for the interference-free of these two steps. We implement our methods and present machining results. All of these two kinds of cutter paths are computed rapidly and automatically.

Contouring medial surface of thin plate structure using local marching cubes

This paper describes an algorithm for contouring a medial surface from CT (computed tomography) data of a thin plate structure. Thin plate structures are common in mechanical structures such as car body shells. When designing the thin plate structures in CAD (computer aided design) and CAE (computer aided engineering) systems, their shapes are usually represented as surface models associated with their thickness values. In this research we are aiming at extracting medial surface models of a thin plate structure from its CT data so as to be used in CAD and CAE systems. However, in such CT data, each voxel in region around the medial surface can not be classified inside or outside, so we can not easily apply iso-surfacing method to contour the medial surface. From the above motives, we first extract medial cells (cubes comprising eight neighboring voxels) from the CT data using a skeletonization method so as to apply marching cubes algorithm to extract the medial surface. It is not, however, guaranteed that the marching cubes algorithm can contour those medial cells (in short, not marching cubeable). We developed cell operations which correct topological connectivity so as to guarantee such marching cubeability. We then apply our method to assign virtual signs to the voxels to apply the marching cubes algorithm. And last, we map thicknesses of thin plate structure to the triangle meshes as textures. A prototype system is developed to show some experimental results.