Real-time nonphotorealistic rendering

TLDR

Nonphotorealistic rendering (NPR) simplifies complex objects into comprehensible line drawings, yet current NPR is mainly a batch process. This paper introduces a real‑time NPR renderer that trades accuracy for speed and provides a tool to significantly improve system performance. The renderer determines visible lines and surfaces using a modified Appel hidden‑line algorithm grounded in the topology of singular maps, a technique applicable to any NPR system requiring visibility descriptions. The system supports multiple NPR styles and renders complex models at interactive frame rates. © CR.

Abstract

Nonphotorealistic rendering (NPR) can help make comprehensible but simple pictures of complicated objects by employing an economy of line. But current nonphotorealistic rendering is primarily a batch process. This paper presents a real-time nonphotorealistic renderer that deliberately trades accuracy and detail for speed. Our renderer uses a method for determining visible lines and surfaces which is a modification of Appel’s hidden-line algorithm, with improvements which are based on the topology of singular maps of a surface into the plane. The method we describe for determining visibility has the potential to be used in any NPR system that requires a description of visible lines or surfaces in the scene. The major contribution of this paper is thus to describe a tool which can significantly improve the performance of these systems. We demonstrate the system with several nonphotorealistic rendering styles, all of which operate on complex models at interactive frame rates. CR