Customizable Strokes for Localized Stylization of View-Dependent Lines Extracted from 3D Models

Abstract

We propose a method to stylize individual lines and preserve their properties as the viewpoint is modified. As the camera position changes and view-dependent lines move across the surface, we track each line in order to extract and store the areas of the surface in which they appear. Each line has an unique reference that we use to check an indexed table from which we can recover its stylization after arbitrary camera movements. We call this region the tracked area of the line. Additionally, we provide a method for line segmentation of occluding contours. In our algorithm, we divide the contour lines at inflection points in order to segment them in a way that is suited for localized stylization as well as to better approximate artist strokes. We also optimize the line tracking process by making use of the Gaussian curvature to separate the elliptic and hyperbolic areas of the surface. In this paper we show how each line only appears in a limited area of the surface corresponding to its tracked area. We also discuss how to eliminate the over-segmentation caused by numerical instability of the approximations in polygonal surfaces as well as how smoothing can be used in order to deal with highly detailed models. Finally, we highlight the achievements of our system for localized stylization of the contour lines of 3D models.

A Survey of Surface‐Based Illustrative Rendering for Visualization

“…For this purpose, Neumann et al . [NIC07] as well as Cardona and Saito [CS15] combine object‐space and image‐space methods to allow illustrators to interactively apply local stroke stylization, for example for technical and medical illustrative visualization (e.g. [NIC07]).…”

Temporally Coherent and Artistically Intended Stylization of Feature Lines Extracted from 3D Models

“…Figure 9 shows the result for a complex animated sequence that combines rotation along two different axis and radical close-up. For comparison purposes, we also provide the results obtained by directly using the stylization goal of a previous localized stylization method [CS15], which is by nature discontinuous in time. Unfortunately, the impact of stylization discontinuities and temporal coherence is difficult to convey in static images.…”

“…Image-space algorithms tend to produce reasonably appealing line drawings but are prone to noise problems and are not suited for complex stylization [ST90,Dec96,Her99,LMLH07]. As stated by Cardona et al [CS15], a common problem of line extraction algorithms is that they usually produce either too many lines that would not be drawn by artists or not enough to convey the shape of the objects being depicted. A particularly relevant category is object-space methods for extracting viewdependent feature lines such as occluding contours [K * 84], suggestive contours [DFRS03,DFR04] and apparent ridges [JDA07].…”

“…In this paper, we assume that the goal style parameterization g(t, s) is already defined using a localized stylization method such as Cardona et al [CS15]. In this paper, we assume that the goal style parameterization g(t, s) is already defined using a localized stylization method such as Cardona et al [CS15].…”

“…Localized stylization methods may produce additional events of stylization discontinuities. In our case, we use Cardona et al method [CS15], which is based on line matching and produces the following additional types of events:…”