A Simple Method to Animate Vegetation in Images Using Simulation-Guided Grid-Based Warping

In this paper, we propose a simple method to animate vegetation in images. The proposed method enables users to interactively animate vegetation in real-time. It can be used to enhance a vegetation photograph or painting with animated motions as well as to help animators to create cartoon animation of vegetation. Our method is suitable for simulating vegetation-wind interaction for a dense vegetation field which exhibit non-rigid property, especially in cartoon style images. In our method, wind field is modeled using fluid simulation. We adopt a harmonic oscillator based on wave simulation as the numerical model for the dynamics of vegetation. The velocity generated from the wind field is used to drive the wave simulation to determine the velocity of vegetation. Based on the velocity of vegetation, we employ a grid-based warping approach to animate different types of vegetation such as grass and trees. As a result, for vegetation in images, we can simulate grass and trees swaying in wind as well as under water plants swaying in water. Our method can produce natural-looking output motions comparable with real cartoons. Users can interactively control the location of the source, direction and strength of the wind or water flow and the property of vegetation on the fly.