Grass Mapping: Realistic Real Time Grass Rendering

Current real time grass implementations are ill-suited for the task of rendering short lawns effectively and cheaply. We present a method using dynamic texture creation. We represent a patch of grass by a special bitmap termed the Grass Source Map . Much the same way height maps supply the information used to generate a terrain, this map effectively supplies the blueprints for building the geometry we use for a square patch of lawn. We propose a method for building, sorting and rendering the geometry this map represents using vertex shaders. Instead of rendering the geometry to our scene however, we render to an off screen target surface, producing a tiling 2D texture termed the Grass Map.” This texture map is mapped over an arbitrary terrain, giving the illusion that countless blades of grass are being rendered. Our method combines the visual quality of rendering the correct geometric orientation and lighting of individual grass blades, while maintaining the low overhead of texture tiling. We thus provide a novel grass rendering option where we render a small number of grass blades at a fixed cost, and reuse that work to build an effective grass simulation