Abstract

Two approaches, image-space and object-space, exist for non-photorealistic rendering (NPR). The object-space approach has an advantage that it is able to access the 3D shape information of the scene with a 3D model. In this paper, we present a non-stroke based image-space technique that has the strength similar to that of the object-space approach, but without involving explicit 3D models. The basic idea is to factorise the Lambertian model to obtain the shape and texture information implicitly contained in the image. We also develop a specific anisotropic low-pass image filter, which can smooth an image without blurring important features. With the developed techniques, we present two NPR styles, the sketching style and the painting style. Although our work does not aim to mimic any specific existing art form, the sketching style can generate effects similar to those of the pen-and-ink and the painting style is able to produce the colour permeating effects of watercolour.