Feature-based Product Modelling in a Collaborative Environment

Ph.DDOCTOR OF PHILOSOPH

Integration between Creativity and Engineering in Industrial Design

The objective of the paper is to illustrate which are the key issues today in the industrial design workflow, paying particular attention to the most creative part of the workflow, highlighting those nodes which still make hard the styling activities and giving a brief survey of the researches aimed at smoothing the transfer of the design intent along the whole design cycle and at providing tools even more adhering at the mentality of creative people. Based on the experience gained working in two different European projects, through the collaboration with industrial designers in the automotive and the household supplies fields, a general industrial design workflow will be depicted, highlighting the main differences between the automotive and non-automotive sectors; the problems still present in the design activity will be also illustrated. The paper includes short surveys, in relation to the aesthetic design, in matter of research activities aimed at - identifying the links between shape characteristics of a product and the transmitted emotions - better supporting, in a digital way, the 2D sketching phase and the automatic interpretation and transfer of the 2D sketches into a 3D surface model - improving the 3D Modeling phase

HairBrush for Immersive Data-Driven Hair Modeling

International audienceWhile hair is an essential component of virtual humans, it is also one of the most challenging digital assets to create. Existing automatic techniques lack the generality and flexibility to create rich hair variations, while manual authoring interfaces often require considerable artistic skills and efforts, especially for intricate 3D hair structures that can be difficult to navigate. We propose an interactive hair modeling system that can help create complex hairstyles in minutes or hours that would otherwise take much longer with existing tools. Modelers, including novice users, can focus on the overall hairstyles and local hair deformations, as our system intelligently suggests the desired hair parts. Our method combines the flexibility of manual authoring and the convenience of data-driven automation. Since hair contains intricate 3D structures such as buns, knots, and strands, they are inherently challenging to create using traditional 2D interfaces. Our system provides a new 3D hair author-ing interface for immersive interaction in virtual reality (VR). Users can draw high-level guide strips, from which our system predicts the most plausible hairstyles via a deep neural network trained from a professionally curated dataset. Each hairstyle in our dataset is composed of multiple variations, serving as blend-shapes to fit the user drawings via global blending and local deformation. The fitted hair models are visualized as interactive suggestions that the user can select, modify, or ignore. We conducted a user study to confirm that our system can significantly reduce manual labor while improve the output quality for modeling a variety of head and facial hairstyles that are challenging to create via existing techniques

Toolpath interpolation and smoothing for computer numerical control machining of freeform surfaces : a review

Driven by the ever increasing demand in function integration, more and more next generation high value-added products, such as head-up displays, solar concentrators and intra-ocular-lens, etc., are designed to possess freeform (i.e., non-rotational symmetric) surfaces. The toolpath, composed of high density of short linear and circular segments, is generally used in computer numerical control (CNC) systems to machine those products. However, the discontinuity between toolpath segments leads to high-frequency fluctuation of feedrate and acceleration, which will decrease the machining efficiency and product surface finish. Driven by the ever-increasing need for high-speed high-precision machining of those products, many novel toolpath interpolation and smoothing approaches have been proposed in both academia and industry, aiming to alleviate the issues caused by the conventional toolpath representation and interpolation methods. This paper provides a comprehensive review of the state-of-the-art toolpath interpolation and smoothing approaches with systematic classifications. The advantages and disadvantages of these approaches are discussed. Possible future research directions are also offered

Towards recovery of complex shapes in meshes using digital images for reverse engineering applications

When an object owns complex shapes, or when its outer surfaces are simply inaccessible, some of its parts may not be captured during its reverse engineering. These deficiencies in the point cloud result in a set of holes in the reconstructed mesh. This paper deals with the use of information extracted from digital images to recover missing areas of a physical object. The proposed algorithm fills in these holes by solving an optimization problem that combines two kinds of information: (1) the geometric information available on the surrounding of the holes, (2) the information contained in an image of the real object. The constraints come from the image irradiance equation, a first-order non-linear partial differential equation that links the position of the mesh vertices to the light intensity of the image pixels. The blending conditions are satisfied by using an objective function based on a mechanical model of bar network that simulates the curvature evolution over the mesh. The inherent shortcomings both to the current holefilling algorithms and the resolution of the image irradiance equations are overcom

Interactive freeform editing techniques for large-scale, multiresolution level set models

Level set methods provide a volumetric implicit surface representation with automatic smooth blending properties and no self-intersections. They can handle arbitrary topology changes easily, and the volumetric implicit representation does not require the surface to be re-adjusted after extreme deformations. Even though they have found some use in movie productions and some medical applications, level set models are not highly utilized in either special effects industry or medical science. Lack of interactive modeling tools makes working with level set models difficult for people in these application areas.This dissertation describes techniques and algorithms for interactive freeform editing of large-scale, multiresolution level set models. Algorithms are developed to map intuitive user interactions into level set speed functions producing specific, desired surface movements. Data structures for efficient representation of very high resolution volume datasets and associated algorithms for rapid access and processing of the information within the data structures are explained. A hierarchical, multiresolution representation of level set models that allows for rapid decomposition and reconstruction of the complete full-resolution model is created for an editing framework that allows level-of-detail editing. We have developed a framework that identifies surface details prior to editing and introduces them back afterwards. Combining these two features provides a detail-preserving level set editing capability that may be used for multi-resolution modeling and texture transfer. Given the complex data structures that are required to represent large-scale, multiresolution level set models and the compute-intensive numerical methods to evaluate them, optimization techniques and algorithms have been developed to evaluate and display the dynamic isosurface embedded in the volumetric data.Ph.D., Computer Science -- Drexel University, 201

Convolution filtering of continuous signed distance fields for polygonal meshes

Signed distance fields obtained from polygonal meshes are commonly used in various applications. However, they can have C1 discontinuities causing creases to appear when applying operations such as blending or metamorphosis. The focus of this work is to efficiently evaluate the signed distance function and to apply a smoothing filter to it while preserving the shape of the initial mesh. The resulting function is smooth almost everywhere, while preserving the exact shape of the polygonal mesh. Due to its low complexity, the proposed filtering technique remains fast compared to its main alternatives providing C1-continuous distance field approximation. Several applications are presented such as blending, metamorphosis and heterogeneous modelling with polygonal meshes

High-performance geometric vascular modelling

Image-based high-performance geometric vascular modelling and reconstruction is an essential component of computer-assisted surgery on the diagnosis, analysis and treatment of cardiovascular diseases. However, it is an extremely challenging task to efficiently reconstruct the accurate geometric structures of blood vessels out of medical images. For one thing, the shape of an individual section of a blood vessel is highly irregular because of the squeeze of other tissues and the deformation caused by vascular diseases. For another, a vascular system is a very complicated network of blood vessels with different types of branching structures. Although some existing vascular modelling techniques can reconstruct the geometric structure of a vascular system, they are either time-consuming or lacking sufficient accuracy. What is more, these techniques rarely consider the interior tissue of the vascular wall, which consists of complicated layered structures. As a result, it is necessary to develop a better vascular geometric modelling technique, which is not only of high performance and high accuracy in the reconstruction of vascular surfaces, but can also be used to model the interior tissue structures of the vascular walls.This research aims to develop a state-of-the-art patient-specific medical image-based geometric vascular modelling technique to solve the above problems. The main contributions of this research are:- Developed and proposed the Skeleton Marching technique to reconstruct the geometric structures of blood vessels with high performance and high accuracy. With the proposed technique, the highly complicated vascular reconstruction task is reduced to a set of simple localised geometric reconstruction tasks, which can be carried out in a parallel manner. These locally reconstructed vascular geometric segments are then combined together using shape-preserving blending operations to faithfully represent the geometric shape of the whole vascular system.- Developed and proposed the Thin Implicit Patch method to realistically model the interior geometric structures of the vascular tissues. This method allows the multi-layer interior tissue structures to be embedded inside the vascular wall to illustrate the geometric details of the blood vessel in real world

The Application of Zeeko Polishing Technology to Freeform Femoral Knee Replacement Component Manufacture

The purpose of this study was to develop an advanced 7-axis Computer Numerical Controlled (CNC) Polishing Machine from its successful original application of industrial optics manufacture into a process for the manufacture of femoral knee components to improve wear characteristics and prolong component lifetimes. It was indentified that the successful manufacture of optical components using a corrective polishing procedure to enhance their performance could be applied to femoral knee implant components. Current femoral knee implants mimic the natural shape of the joint and are freeform (no axis of symmetry) in nature hence an advanced CNC polishing machine that can follow the contours associated with such shapes could improve surface finish and conformity of replacement femoral knee bearing surfaces, leading to improved performance. The process involved generating machine parameters that would optimize the polishing procedure to minimize wear of materials used in femoral knee implant manufacture. Secondly a design of a Non-Uniform Refind B-Spline (NURBS) model for control of the Polishing Machine over the freeform contours of the femoral component. Completing the process involved development of a corrective polishing process that would improve form control of the components. Such developments would improve surface finish and conformity which are well documented contributors to wear and hence the lifeline of orthopaedic implants. By the means of comparison of this technique to that of a conventional finishing technique using pin-on-plate disc testing it was concluded that performance of the CNC polished components was an improvement on that of the conventional technique. In the case of form control their were slight indications through small decreases in peak to valley (PV) error that the process helped reduce form error and could increase the lifetime of femoral knee replacement components. The overall study provided results that indicate the the Zeeko process could be used in the application of polishing of hard-on-hard material combinations to improve form control without compromising surface finish hence improving lifetimes of the implant. The results have their limitations in the fact that the wear test performance was only carried out on orthopaedic implant materials using a pin-on-plate wear test rig. Due to the time limitations on the thesis it can be said that further analysis of correcting form without compromising surface finish on entire implant systems under full joint simulator testing which would provide mre realistic contitions would a more definitive answer be achieved