Study On The Strokes Of3D Sketching For Automotive Styling

For the automotive styling, the frames have been created consciously with3Dfreehand strokes. These frames could express the designers’ inspiration in minds, and theyare different from those created by CAS/CAD (Computer Aided Styling/Computer AidedDesign) technology. In this paper, the study focuses on the combination of strokes in aplane or in space. The traditional automotive sketching with paper and pen is free, fast andsimple. However, it has some weaknesses. For example, styling has been constrained byenvironment, the sketches are difficult to be saved and modified, and these sketches can notbe used directly to establish the3D model for the downstream processing in the industrialsoftware such as Catia, UG or ProE. Therefore, the fitting of strokes has been developed asa bridge between the traditional2D sketching and3D digital modeling. The designers coulduse digital tablet and pen to sketch a vehicle’s frame in3D. These3D frames could be usedin engineering software for establishing the surfaces in CAD. Finally, it would shorten thedevelopment period of vehicle.This paper aims to study the fitting of3D strokes. It can be divided into four steps:Firstly, this paper aims to study the single stroke including the nature andcharacteristics. The processes of single stroke include the compression and storage of thepoints, the identification of stroke separating and closing, and the direction of strokes andtheir standardization. The algorithms of fitting include the monomial fitting, theleast-squares fitting and the parametric fitting.Secondly, the real-time multi-stroke fitting has been developed from a single stroke totwo adjacent strokes, and more strokes that will meet the nature habits of styling. Theresearch will focus on the relationship between the adjacent strokes, in order to find areal-time and effective method to do the multi-stroke fitting. The whole points in twostrokes are used for the interpolation based on the methods of the choral ratios and thehybrid weight. In addition, the methods of real-time fitting and modifying by using thepartial points of strokes have also been proposed for the local modification, named λ-fittingalgorithm and modification algorithm. However, it found that using part points tointerpolate would match the original curve shape better. Thirdly, from2D to3D, this study aims to create the3D strokes by reducing thedimension. There are two planes. One is parallel to the computer screen. Another isperpendicular to it. The strokes located in the two planes would fit together into a spatialstroke.Fourthly, from plane to surface, the spatial stroke is created by two surfaces, which isactually the intersectional line of the two surfaces. The shape of two surfaces could becontrolled by the strokes in the screen and the working plane. If the shape of the twostrokes has been modified, the shape of the surfaces would be modified too. So that the3Dstrokes could be modified in the same time. As a result, the3D strokes have been used toestablish the3D frames of vehicle.