Nobuyuki Umetani

Guided exploration of physically valid shapes for furniture design

Geometric modeling and the physical validity of shapes are traditionally considered independently. This makes creating aesthetically pleasing yet physically valid models challenging. We propose an interactive design framework for efficient and intuitive exploration of geometrically and physically valid shapes. During any geometric editing operation, the proposed system continuously visualizes the valid range of the parameter being edited. When one or more constraints are violated after an operation, the system generates multiple suggestions involving both discrete and continuous changes to restore validity. Each suggestion also comes with an editing mode that simultaneously adjusts multiple parameters in a coordinated way to maintain validity. Thus, while the user focuses on the aesthetic aspects of the design, our computational design framework helps to achieve physical realizability by providing active guidance to the user. We demonstrate our framework on plank-based furniture design with nail-joint and frictional constraints. We use our system to design a range of examples, conduct a user study, and also fabricate a physical prototype to test the validity and usefulness of the system.

Sensitive couture for interactive garment modeling and editing

We present a novel interactive tool for garment design that enables, for the first time, interactive bidirectional editing between 2D patterns and 3D high-fidelity simulated draped forms. This provides a continuous, interactive, and natural design modality in which 2D and 3D representations are simultaneously visible and seamlessly maintain correspondence. Artists can now interactively edit 2D pattern designs and immediately obtain stable accurate feedback online, thus enabling rapid prototyping and an intuitive understanding of complex drape form.

Cross-sectional structural analysis for 3D printing optimization

We propose a novel cross-sectional structural analysis technique that efficiently detects critical stress inside a 3D object. We slice the object into cross-sections and compute stress based on bending momentum equilibrium. Unlike traditional approaches based on finite element methods, our method does not require a volumetric mesh or solution of linear systems, enabling interactive analysis speed. Based on the stress analysis, the orientation of an object is optimized to increase mechanical strength when manufactured with 3D printing.

Pteromys: interactive design and optimization of free-formed free-flight model airplanes

This paper introduces novel interactive techniques for designing original hand-launched free-flight glider airplanes which can actually fly. The aerodynamic properties of a glider aircraft depend on their shape, imposing significant design constraints. We present a compact and efficient representation of glider aerodynamics that can be fit to real-world conditions using a data-driven method. To do so, we acquire a sample set of glider flight trajectories using a video camera and the system learns a nonlinear relationship between forces on the wing and wing shape. Our acquisition system is much simpler to construct than a wind tunnel, but using it we can efficiently discover a wing model for simple gliding aircraft. Our resulting model can handle general free-form wing shapes and yet agrees sufficiently well with the acquired airplane flight trajectories. Based on this compact aerodynamics model, we present a design tool in which the wing configuration created by a user is interactively optimized to maximize flight-ability. To demonstrate the effectiveness of our tool for glider design by novice users, we compare it with a traditional design workflow.

Bicuspid aortic valves undergo excessive strain during opening: A simulation study

OBJECTIVE The objective of this study was to examine the influence of the morphologic characteristics of the bicuspid aortic valve on its disease progression by comparing the motion, stress/strain distribution, and blood flow of normal and stenotic tricuspid valves using simulation models. METHODS Bicuspid, stenotic tricuspid with commissural fusion or thickened leaflet, and normal aortic valves were modeled with internal blood flow. Blood flow and the motion of aortic valve leaflets were studied using fluid-structure interaction finite element analysis, and stress/strain (curvature) distributions were calculated during the cardiac cycle. To mimic disease progression, we modified the local thickness of the leaflet where the bending stress was above a threshold. RESULTS Transvalvular pressure gradient was greater in the bicuspid valve compared with the stenotic tricuspid valve with a similar valvular area. The bending strain (curvature) increased in both stenotic tricuspid and bicuspid valves, but a greater increase was observed in the bicuspid valve, and this was concentrated on the midline of the fused leaflets. During disease progression analysis, severity of the stenosis increased only in the bicuspid aortic valve model in terms of valvular area and pressure gradient. CONCLUSIONS The characteristic morphology of the bicuspid valve creates excessive bending strain on the leaflets during ventricular ejection. Such mechanical stress may be responsible for the rapid progression of this disease.

Real-time example-based elastic deformation

We present an example-based elastic deformation method that runs in real time. Example-based elastic deformation was originally presented by Martin et al. [MTGG11], where an artist can intuitively control elastic material behaviors by simply giving example poses. Their FEM-based approach is, however, computationally expensive requiring nonlinear optimization, which hinders its use in real-time applications such as games. Our contribution is to formulate an analogous concept using the shape matching framework, which is fast, robust, and easy to implement. The key observation is that each overlapping local regions right stretch tensor obtained by polar decomposition is a natural choice for a deformation descriptor. This descriptor allows us to represent the pose space as a linear blending of examples. At each time step, the current deformation descriptor is linearly projected onto the example manifold, and then used to modify the rest shape of each local region when computing goal positions. Our approach is two orders of magnitude faster than Martin et al.s approach while producing comparable example-based elastic deformations.

Sketch-based Dynamic Illustration of Fluid Systems

This paper presents a lightweight sketching system that enables interactive illustration of complex fluid systems. Users can sketch on a 2.5-dimensional (2.5D) canvas to design the shapes and connections of a fluid circuit. These input sketches are automatically analyzed and abstracted into a hydraulic graph, and a new hybrid fluid model is used in the background to enhance the illustrations. The system provides rich simple operations for users to edit the fluid system incrementally, and the new internal flow patterns can be simulated in real time. Our system is used to illustrate various fluid systems in medicine, biology, and engineering. We asked professional medical doctors to try our system and obtained positive feedback from them.

FlatFitFab: interactive modeling with planar sections

We present a comprehensive system to author planar section structures, common in art and engineering. A study on how planar section assemblies are imagined and drawn guide our design principles: planar sections are best drawn in-situ, with little foreshortening, orthogonal to intersecting planar sections, exhibiting regularities between planes and contours. We capture these principles with a novel drawing workflow where a single fluid user stroke specifies a 3D plane and its contour in relation to existing planar sections. Regularity is supported by defining a vocabulary of procedural operations for intersecting planar sections. We exploit planar structure properties to provide real-time visual feedback on physically simulated stresses, and geometric verification that the structure is stable, connected and can be assembled. This feedback is validated by real-world fabrication and testing. As evaluation, we report on over 50 subjects who all used our system with minimal instruction to create unique models.

Motion Amplifiers: Sketching Dynamic Illustrations Using the Principles of 2D Animation

We present a sketching tool for crafting animated illustrations that contain the exaggerated dynamics of stylized 2D animations. The system provides a set of motion amplifiers which implement a set of established principles of 2D animation. These amplifiers break down a complex animation effect into independent, understandable chunks. Each amplifier imposes deformations to an underlying grid, which in turn updates the corresponding strokes. Users can combine these amplifiers at will when applying them to an existing animation, promoting rapid experimentation. By leveraging the freeform nature of sketching, our system allows users to rapidly sketch, record motion, explore exaggerated dynamics using the amplifiers, and fine-tune their animations. Practical results confirm that users with no prior experience in animation can produce expressive animated illustrations quickly and easily.

A Kinematic Approach for Efficient and Robust Simulation of the Cardiac Beating Motion

Computer simulation techniques for cardiac beating motions potentially have many applications and a broad audience. However, most existing methods require enormous computational costs and often show unstable behavior for extreme parameter sets, which interrupts smooth simulation study and make it difficult to apply them to interactive applications. To address this issue, we present an efficient and robust framework for simulating the cardiac beating motion. The global cardiac motion is generated by the accumulation of local myocardial fiber contractions. We compute such local-to-global deformations using a kinematic approach; we divide a heart mesh model into overlapping local regions, contract them independently according to fiber orientation, and compute a global shape that satisfies contracted shapes of all local regions as much as possible. A comparison between our method and a physics-based method showed that our method can generate motion very close to that of a physics-based simulation. Our kinematic method has high controllability; the simulated ventricle-wall-contraction speed can be easily adjusted to that of a real heart by controlling local contraction timing. We demonstrate that our method achieves a highly realistic beating motion of a whole heart in real time on a consumer-level computer. Our method provides an important step to bridge a gap between cardiac simulations and interactive applications.