SYSTEM AND METHOD FOR MULTI-VOLUME RENDERING

System (100), method and computer program product for direct multi-volume rendering. 3D data specify a three-dimensional scene with a plurality of volumes (290). Each voxel of a particular volume has a scalar value being the result of an imaging procedure for the measurement of a physical property of an imaging subject. A multi-ray generator (230) generates a view multi-ray in the direction of a particular pixel of a projection image, wherein the particular pixel represents a 2D projection of all scene voxels intersecting with the view multi-ray behind the projection image. A volume ray marching processor (240) processes each view ray in its associated volume using volume ray marching, wherein, at each ray marching step, the scalar value of the corresponding voxel is mapped to a color value and a transparency value of said corresponding voxel. A projection image updater (250) updates the value of the particular pixel in the projection image by combining the respective voxel color and transparency values of the individual view rays. Updating with the values of a particular voxel intersecting with a particular view ray is performed after the updating with all intersecting voxel values of voxels closer to the viewing point than the particular voxel.