We present the usage of a non-discrete degree of interest (DOI) function, obtained by brushing multi-valued 3D simulation data in information visualization views, to define opacity, color, and geometrical transfer functions for 3D rendering in a scientific visualization view via linking. To reflect the smooth nature of features in flow simulation data, smooth brushing was chosen. Different available views and interaction methods of a prototype system are discussed, and examples from 3D flow simulation are shown.