Jun Mitani

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.

SketchChair: an all-in-one chair design system for end users

SketchChair is an application that allows novice users to control the entire process of designing and building their own chairs. Chairs are designed using a simple 2D sketch-based interface and design validation tools, and are then fabricated from sheet materials, cut by a laser cutter or CNC milling machine. This paper presents the concepts and details of SketchChair, and both miniature and full-sized chairs are designed using the application. We conclude with results and insights from a workshop in which novice users designed their own model chairs.

Converting 3D furniture models to fabricatable parts and connectors

Although there is an abundance of 3D models available, most of them exist only in virtual simulation and are not immediately usable as physical objects in the real world. We solve the problem of taking as input a 3D model of a man-made object, and automatically generating the parts and connectors needed to build the corresponding physical object. We focus on furniture models, and we define formal grammars for IKEA cabinets and tables. We perform lexical analysis to identify the primitive parts of the 3D model. Structural analysis then gives structural information to these parts, and generates the connectors (i.e. nails, screws) needed to attach the parts together. We demonstrate our approach with arbitrary 3D models of cabinets and tables available online.

3D sketch: sketch-based model reconstruction and rendering

We propose a new modeling and rendering system that enables users to construct 3D models with an interface that seems no different from sketching by hand, and that displays models in a sketch-like style, preserving the features of the users strokes. We call this system 3D SKETCH. To reconstruct 3D objects from sketches, we limit the domain of renderable sketches and prepare a template for interpreting sketches. As long as a sketch can be matched to such a template, the system can reconstruct a mesh model from the sketch. The system collects information about strokes made, and uses that information for our rendering scheme.

Modeling-in-context: user design of complementary objects with a single photo

The products that we use everyday are typically designed and produced for mass consumption. However, it is difficult for such products to satisfy the needs of individual users. We present a framework that allows the end-user to participate in the entire process of designing their own objects, from the initial concept stage to the production of a new real-world object that fits well with the existing complementary objects. We advocate using a single photo as a rough guide for the user to sketch a new customized object that does not exist in the photo. Our system provides a 2D interface for sketching the outline of the new object and annotating certain geometric properties of it directly on the photo. We introduce a Modified Lipson optimization method for generating the 3D shape. We design a variety of real-world everyday objects that are complementary to the existing objects and environment in the photo. We show that novice users can learn and create new objects with our system within minutes.

Spatial sketch: bridging between movement & fabrication

Spatial Sketch is a three-dimensional (3D) sketch application that bridges between physical movement and the fabrication of objects in the real world via cut planar materials. This paper explores the rationale and details behind the development of the Spatial Sketch application, and presents our observations from user testing and a hands-on lamp shade design workshop. Finally we reflect upon the relevance of embodied forms of human computer interaction for use in digital fabrication.

Retrieval and Visualization of Human Motion Data via Stick Figures

We propose 2D stick figures as a unified medium for visualizing and searching for human motion data. The stick figures can express a wide range or human motion, and they are easy to be drawn by people without any professional training. In our interface, the user can browse overall motion by viewing the stick figure images generated from the database and retrieve them directly by using sketched stick figures as an input query. We started with a preliminary survey to observe how people draw stick figures. Based on the rules observed from the user study, we developed an algorithm converting motion data to a sequence of stick figures. The feature‐based comparison method between the stick figures provides an interactive and progressive search for the users. They assist the users sketching by showing the current retrieval result at each stroke. We demonstrate the utility of the system with a user study, in which the participants retrieved example motion segments from the database with 102 motion files by using our interface.

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

Situated modeling: a shape-stamping interface with tangible primitives

Existing 3D sketching methods typically allow the user to draw in empty space which is imprecise and lacks tactile feedback. We introduce a shape-stamping interface where users can model with tangible 3D primitive shapes. Each of these shapes represents a copy or a fragment of the construction material. Instead of modeling in empty space, these shapes allow us to use the real-world environment and other existing objects as a tangible guide during 3D modeling. We call this approach Situated Modeling: users can create new real-sized 3D objects directly in 3D space while using the nearby existing objects as the ultimate reference. We also describe a two-handed shape-stamping technique for stamping with tactile feedback. We show a variety of doit-yourself furniture and household products designed with our system, and perform a user study to compare our method with a related AR-based modeling system.

Beady: interactive beadwork design and construction

Beadwork is the art of connecting beads together by wires. While common beadwork is two-dimensional (2D), three-dimensional (3D) beadwork is also popular in oriental regions such as Japan and China. However, the design and construction of 3D beadwork is very difficult. The final shape is defined by the complicated three-dimensional interaction between beads and wires, thus making it very difficult to design manually. One also needs to specify an appropriate wire path to hold the beads together and to manually insert the wire into the beads one by one following the path to construct the beadwork. Careful observation of existing beadwork structures shows several geometrically interesting problems, which make beadwork design an interesting technical challenge.