A simulation on grass swaying with dynamic wind force

Abstract

Grass swaying simulation with respect to wind force plays an important role in the outdoor scene design of video games and animations. However, the complex and dynamic interactions between grass and wind largely hinder the existing approaches from generating physically plausible simulation in real-time performance. Therefore, common approaches compromise by either rendering still meadow or simply adopting a procedural method for simulating the grass motion. In this work, we present a simple yet effective grass model that enables the real-time simulation of grass swaying mimicking real-world grass motions under dynamic wind force. We characterize each individual grass using a simple polyline model with four vertices derived from the control knots of a cubic Bezier curve describing the real grass shape. The grass dynamics is modeled by applying a combination of swinging, bending and twisting motions to the polyline model in response to the input wind force. The deformed grass model is then passed to the shader pipeline to synthesize grass blades for the rendering. Experimental results show that our system not only achieves real-time performance in simulation and rendering, but also scales well to large grass field such as a meadow.