Nobuyuki Umezu

Automatic detection of the optimal ejecting direction based on a discrete Gauss map

Abstract In this paper, the authors propose a system for assisting mold designers of plastic parts. With a CAD model of a part, the system automatically determines the optimal ejecting direction of the part with minimum undercuts. Since plastic parts are generally very thin, many rib features are placed on the inner side of the part to give sufficient structural strength. Our system extracts the rib features from the CAD model of the part, and determines the possible ejecting directions based on the geometric properties of the features. The system then selects the optimal direction with minimum undercuts. Possible ejecting directions are represented as discrete points on a Gauss map. Our new point distribution method for the Gauss map is based on the concept of the architectural geodesic dome. A hierarchical structure is also introduced in the point distribution, with a higher level “rough” Gauss map with rather sparse point distribution and another lower level “fine” Gauss map with much denser point distribution. A system is implemented and computational experiments are performed. Our system requires less than 10 seconds to determine the optimal ejecting direction of a CAD model with more than 1 million polygons.

Fast safety verification of interior parts of automobiles

A program for automatically verifying safety regulations specified on the interior part of the automobile is developed. In the ECE regulation, any surface of the interior part is requested to have roundness larger than R3.2 where a sphere of diameter 165mm can collide. Our developed program initially generates points sufficiently covering the visible surface of the model. For each point, sphere-object intersections associated with the regulations are evaluated. If the surface portion around the point cannot satisfy the geometric condition of the regulation, red color is painted to the point. As the result, corner shapes of the CAD model with possibly injuring the driver and passenger in the car crash are extracted and displayed.

Thickness and clearance visualization based on distance field of 3D objects

Abstract This paper proposes a novel method for visualizing the thickness and clearance of 3D objects in a polyhedral representation. The proposed method uses the distance field of the objects in the visualization. A parallel algorithm is developed for constructing the distance field of polyhedral objects using the GPU. The distance between a voxel and the surface polygons of the model is computed many times in the distance field construction. Similar sets of polygons are usually selected as close polygons for close voxels. By using this spatial coherence, a parallel algorithm is designed to compute the distances between a cluster of close voxels and the polygons selected by the culling operation so that the fast shared memory mechanism of the GPU can be fully utilized. The thickness/clearance of the objects is visualized by distributing points on the visible surfaces of the objects and painting them with a unique color corresponding to the thickness/clearance values at those points. A modified ray casting method is developed for computing the thickness/clearance using the distance field of the objects. A system based on these algorithms can compute the distance field of complex objects within a few minutes for most cases. After the distance field construction, thickness/clearance visualization at a near interactive rate is achieved.

GPU-based visualization of knee-form contact area for safety inspections

The United Nations defines a safety regulation based on the possible collision between the driver’s knee and an automobile’s instrument panel. The “knee-form” apparatus used to evaluate compliance with this regulation can be modeled as a Minkowski sum shape of a vertical equilateral triangle and a horizontal cylinder with a radius of 60 mm and a thickness of 120 mm. The knee form contacting condition is geometrically equivalent to that of an equilateral triangle contacting a Minkowski sum shape of the instrument panel and a horizontal cylinder. Based on this concept, we propose a novel algorithm for extracting the knee-form contacting area on the instrument panel. With the parallel computation capability of a Graphics Processing Unit, our system can detect and output the knee-form contacting area in a practical time period.

Shrinking sphere: A parallel algorithm for computing the thickness of 3D objects

AbstractAn interactive system is required to enable machine designers to precisely visualize the thickness of a machine part. The thickness of a 3D object at a surface point is given by the diameter of the maximum inscribed sphere (MIS) touching that point. In this paper, we propose a novel iterative algorithm, namely, the shrinking sphere algorithm, for computing the MIS at a specific surface point. The convergence speed of the proposed algorithm is very high, and several iterations are usually sufficient for obtaining the MIS. The parallel execution of the algorithm with a graphics processing unit (GPU) is presented for further improving the computation speed. On the basis of the proposed algorithm, an experimental thickness visualization system is implemented using Compute Unified Device Architecture (CUDA). This system can visualize the thickness of a complex object with nearly two million polygons in several minutes using a PC (Core i7 CPU, 32GB memory and GTX-980 GPU), which is sufficiently fast for...

Visualization of Potential Sink Marks using Thickness Analysis of Finely Tessellated Solid Model

Abstract Sink marks are unwanted shallow depressions on the molded plastic surface caused by localized shrinkage during the hardening process of injection molding. Sink marks appearing in the exterior impair the aesthetic quality of the product. In this study, a novel method for extracting potential sink marks that can occur on the part surface is proposed. The thicker portion of the part shrinks with a greater amount than that of the thinner portion. This difference in the shrinkage amount is the main cause of the sink mark. In the plastic part design practice, engineers often check the thickness distribution to predict potential sink marks in the part surface. Our method can be considered as an automated technique of such manual inspection task. A polyhedral solid model of the part with sufficiently small triangles of nearly the same size is prepared. The amount of shrinkage at each polygon is estimated based on its thickness and the shrinkage ratio of the part. The developed algorithm extracts the potential sink marks by analyzing the shrinkage distribution on the part surface.

Extraction of vertical cylinder contacting area for motorcycle safety verification

Japanese motorcycle manufacturers define a safety regulation regarding the motorcycle shape to prevent injury to pedestrians in the event of a crash. To satisfy the regulation, the external surface of the motorcycle must have a sufficient degree of roundness if there is any chance that it could contact a vertical cylinder having a diameter of 300 mm approximating the human body. In this paper, we propose a novel method for assisting in the safety regulation inspection. This method extracts the surface regions of the tessellated motorcycle body where the vertical cylindrical column contacts and the surface region radius is less than 4mm. The parallel processing capability of a graphics processing unit (GPU) is used to accelerate the extraction task of identifying the column contacting area. A systemusing our algorithm candetect surface areas on themotorcycle bodywhere the safety regulation is not satisfied.

Fast computation of accessibility cones for assisting 3 + 2 axis milling

In this paper, we propose an algorithm for computing all appropriate cutter postures in the 3 + 2 axis milling of the mold part. As a measure of the appropriateness of the cutter posture, the peak ...

Evaluating the visibility of presentation slides

Presentations using slide software such as PowerPoint are widely performed in offices and schools. The improvement of presentation skills among ordinary people is required because these days such an opportunity of giving presentation is becoming so common. One of the key factors for making successful presentation is the visibility of the slides, as well as the contents themselves. We propose an algorithm to numerically evaluate the visibility of presentation slides. Our method receives a presentation as a set of images and eliminates the background from the slides to extract characters and figures. This algorithm then evaluates the visibility according to the number and size of characters, their colors, and figure layouts. The slide evaluation criteria are based on the series of experiments with 20 participants to parameterize typical values for visual elements in slides. The algorithm is implemented on an iMac and takes 0.5 sec. to evaluate a slide image. The evaluation score is given as a value between 0 and 100 and the users can improve their slide pages with lower scores. Our future work includes a series of experiments with various presentations and extending our method to publish as a web-based rating service for learning presentation skills.

Prototype implementation of mirror with built-in display

People who are unfamiliar with digital equipments might have a feeling of inferiority in the coming ubiquitous computing age. Such a circumstance can be solved with equipments that never seem to be based on digital technology. In this paper, we propose a smart mirror with displays and cameras inside to offer various functions such as portrait logging, appearance self-check, and information display. A prototype implementation with an iMac and a Kinect sensor is presented as well as human detection with a depth template and motion detection to turn on instant logging. Our future work includes completing the development and conducting user experiments.