Abstract: Clouds are an important visual element of any natural scene and computer artists often wish to create specific cloud shapes (for example in the film Amélie, as depicted in Fig 1). We describe a sketch based interface for modeling cumulous clouds. This interface allows rapid construction of a 3D cloud surface representation (mesh) using an underlying point based implicit surface representation. This mesh is rendered using the technique [BNM*08], resulting in a realtime cloud modeling and rendering system.