Features from a Single Vector Pressure Stroke

Qiang Li,Xi Wang,Cuixian Xuan,Zhao Zhang,Changhai Yang,Yongjian Gong

doi:10.1155/2017/5636913

Abstract

Freehand sketching in a real-time 3D styling system presents a different way to create a 3D model from the traditional CAD system. Strokes are the most common and useful objects in the expression of a stylist’s intention by using the gesture commands and in the construction of geometries. Not only are they sketched freely as drawing on a paper with a pen, but also they can be converted automatically into spline curves and then can be used to form a surface. Therefore, it is necessary to investigate the features of stroke, the extraction and identification of these features, and the applications. Here, the features from a single vector pressure stroke have been discussed in detail according to their applications in an automotive freehand styling system in the early stage of conceptual design. The features have been divided into three parts: the input features, the calculable feature, and the added features. Over a hundred features have been defined and classified with the geometry or performance attributes. The features proposed have been applied in the identification of gesture commands, the expression of art vector stroke by pseudoantialiasing method, and a novel method to generate a spatial curve directly by the pressure of stroke in AutoSketch system.

Highlights

Strokes are used in the generation of geometries and applied in many related manipulations to assist sketching, which make the freehand sketching system more natural and suitable for creative design
The most direct application is that the strokes are converted into images in a raster graphics system, for example, in Painter or Photoshop, or transformed into curves in a vector graphic system, for example, TEDDY [1], I Love Sketch system [2], or AutoSketch [3] (Figure 1), which is quite different from the curve generations in the traditional CAD systems
More features have been applied into AutoSketch system for the requirement of real-time 3D sketching [7, 8], especially the pressure information of digital pen that has been used to creature the spatial curve and express the style of stroke, in which more features from the strokes are calculated [9]

Summary

Introduction

Strokes are used in the generation of geometries and applied in many related manipulations to assist sketching, which make the freehand sketching system more natural and suitable for creative design. There are five parts of related research works for the development of AutoSketch system: the combination of multistrokes, the identification of sketched gesture commands, the standardization of freehand sketched geometries, the transformation of curves or surfaces from 2D to 3D, and the application of pressure information. Input method of 3D freehand sketching in automotive styling (Science and Technology Plan Projects of Jinhua City (20111-045)), and 3D automotive freehand styling system based on the pressure of digital pen and the combination of strokes (Science and Technology Plan Projects of Zhejiang Province (2013C31085)). These features can be classified into three parts: input, calculable, and added ones

Input Features

Calculable Features

Number 1 2 3

Added Features

Validation of Features

Conclusions