J.P. Pernot

AESTHETIC DESIGN OF SHAPES USING FULLY FREE-FORM DEFORMATION FEATURES

Geometric models, such as B-Rep or CSG, are often used as a shared reference representation of the product along the whole design process. However, they do not provide capabilities for conveying complex information related to the involved product development tasks. This also applies for the initial styling activity, in which the shape is described by complex mathematical models handled by tools still not sufficiently suited to the creative designer mentality. To overcome these limits, we introduce the so-called Fully Free-Form Deformation Features (δ–F4) concept and the related manipulation tools. Advantages of both the free-form surface deformation method and the feature-based approach are combined to define these high-level modelling entities enabling the direct shape-oriented modification of surfaces through a restricted set of parameters. They are mainly defined by characteristic curves in order to better cope with the curve-oriented designers’ way of working. In addition, a (δ–F4) classification is proposed to enable a fast access to the desired shape. The proposed approach is illustrated with some examples from our prototype software.Geometric models, such as B-Rep or CSG, are often used as a shared reference representation of the product along the whole design process. However, they do not provide capabilities for conveying complex information related to the involved product development tasks. This also applies for the initial styling activity, in which the shape is described by complex mathematical models handled by tools still not sufficiently suited to the creative designer mentality. To overcome these limits, we introduce the so-called Fully Free-Form Deformation Features (δ–F4) concept and the related manipulation tools. Advantages of both the free-form surface deformation method and the feature-based approach are combined to define these high-level modelling entities enabling the direct shape-oriented modification of surfaces through a restricted set of parameters. They are mainly defined by characteristic curves in order to better cope with the curve-oriented designers’ way of working. In addition, a (δ–F4) classification is p...

A hybrid models deformation tool for free-form shapes manipulation

This paper addresses the way models mixing various types of geometric representations (e.g. NURBS curves and patches, polylines, meshes), potentially immersed in spaces of different dimensions (e.g. NURBS patch and its 2D trimming lines), can be deformed simultaneously. The application domains range from the simple deformation of a set of NURBS curves in a 2D sketcher to the simultaneous deformation of meshes, patches as well as trimming lines lying in parametric spaces. The deformation itself results from the solution of an optimization problem defined by a set of geometric constraints and deformation behaviors. This new breakthrough on how geometric models can be manipulated has been made possible thanks to our linear mechanical model of deformation that can be coupled to manifolds of dimension zero (e.g. points, vertices) and one (e.g. edges, segments) whatever the spaces dimension. An extended constraints toolbox is also proposed that enables the specification of both characteristic points/curves and continuity conditions between the various geometric models. The link between the semantics of the deformation behaviors and the geometric models is ensured through the use of multiple minimizations. The approach is illustrated with several examples coming from our prototype software.Copyright

Insertion of Planar Areas Into Free-Form Surfaces in Early Product Design

Surfaces, like planes, cylinders or spheres, are basic primitive surfaces not only for mechanical engineering but also for aesthetic design, world of free-form surfaces, where they are essentially used to answer some functional constraints, like assembling and manufacturing ones, or to achieve specific light effects. The early design steps are characterised by the uncertainty in the definition of the precise geometry and most of the time, product constraints are only partially available. Unfortunately, until now, the insertion of primitive surfaces requires precise curve and surface specifications together with trimming operations, thus imposing that the free-form geometry is recreated each time a modification occurs. In this paper we present a method for the insertion of planar surfaces suitable to handle the uncertainty in the first draft of a product. The approach does not provide effective precise primitive surfaces, but it is able to introduce regions resembling such a behaviour in a free-form surface, without requiring trimming operations, so allowing more efficient shape alternative evaluations.Copyright