Geometry-based shading for shape depiction enhancement

Abstract

Recent works on Non-Photorealistic Rendering (NPR) show that object shape enhancement requires sophisticated effects such as: surface details detection and stylized shading. To date, some rendering techniques have been proposed to overcome this issue, but most of which are limited to correlate shape enhancement functionalities to surface feature variations. Therefore, this problem still persists especially in NPR. This paper is an attempt to address this problem by presenting a new approach for enhancing shape depiction of 3D objects in NPR. We first introduce a tweakable shape descriptor that offers versatile functionalities for describing the salient features of 3D objects. Then to enhance the classical shading models, we propose a new technique called Geometry-based Shading. This technique controls reflected lighting intensities based on local geometry. Our approach works without any constraint on the choice of material or illumination. We demonstrate results obtained with Blinn-Phong shading, Gooch shading, and cartoon shading. These results prove that our approach produces more satisfying results compared with the results of previous shape depiction techniques. Finally, our approach runs on modern graphics hardware in real time, which works efficiently with interactive 3D visualization.

Exhibition and Evaluation of Two Schemes for Determining Hypersurface Curvature in Volumetric Data

“…For example, curvature has been used in segmentation, object recognition, geometric modeling, and analysis of images and volumes [Bib16,Bes86,Bel12,Bag16,Lef18,Sou16], to perform reconstruction in images [Lef17], for biometrics [Sya17], for computer vision-based quality control in manufacturing [Kot18], etc. Other examples include emphasizing features in renderings of meshes [AR18] and images [Hau18], mesh parameterization [Vin17], highlighting shapes in volume renderings [Kin03], and visualization of medical data [Pre16]. In summary, curvature has been quite useful in computer graphics, visualization, and computer vision.…”