Abstract: Generation of dynamic natural scenes is essential for real-time applications, such as simulators or video-games. This paper presents a method for animating and rendering a prairie in real time. The geometric model for the grass relies on three different levels of detail: 3D geometry, volumetric textures (called here 2.5D representation), and 2D textures. The animation of these LODs is controlled through procedural animation primitives that implement wind effects such as slight breeze, gust of wind, whirlwind, or blast of air due to a flying object. Smooth transitions between levels of de-tail are computed on the fly according to camera motion, without stopping the animation. We discuss real-time performance on two platforms: an SGI O2, and an ONYX 2 with an Infinite Reality board.