A system for visualizing a 3D volume, in particular for medical applications, includes an input 1010 for receiving a three-dimensional set of data representing voxel values of the 3D volume. The data set is stored in a storage 1030. A processor projects the volume onto an imaginary 2D projection screen from a predetermined viewpoint. For each pixel of the 2D projection image a ray is cast through the pixel and through the volume. A protocol is used that, while traversing along ray positions within the volume, determines a rendering algorithm and/or rendering parameters in dependence on the ray position. For each ray position the determined rendering algorithm/parameters are used to calculate a contribution to a pixel value of the pixel based on at least one voxel value within a predetermined range of the ray position. An output 1040 is used for providing pixel values of a 2D image for rendering on a display.