2D animation style rendering of water

Abstract

We present a 2D animation style rendering method for water animation. As apparent from the traditional cartoon animations created by artists, 2D water often shows distinct features such as transparency, refraction, and reflection. In an effort to capture and represent the three crucial features in 2D water rendering, we propose a new shading method, cartoon water shader, which is a modified Phong illumination model augmented by the optical properties that ray tracing provides. We also devise a metric to automatically change between transparent refraction and reflection effects based on the angle and distance between the object and camera. This toggle conveniently produces the look and feel of typical 2D water animation. Another essential characteristic in 2D water animation is flow lines. As we assume that an input to our system is a result of any existing fluid simulation, the input mesh contains proper geometric properties. The flow lines can be recovered by computing Gaussian and mean curvature from the input geometry, with which the ridges and valleys are easily identified. We call it a water flow shader. We demonstrate the effectiveness of our method with various examples and discuss the strengths comparing to the previous approaches and prove those things in some analysis.