A system and corresponding method for flexible generation of digitally reconstructed radiograph (DRR) images on a graphics processing unit (GPU) are provided, the system including a processor, an imaging adapter in signal communication with the processor for receiving volumetric data, an integration unit in signal communication with the processor for integrating the volumetric data into incremental line integrals, and a modeling unit in signal communication with the processor for modeling composite line integrals from the incremental line integrals; and the corresponding method including receiving three-dimensional (3D) volumetric data into a graphics pipeline, integrating the 3D volumetric data into incremental line integrals along a plurality of viewing rays, modeling composite line integrals from the incremental line integrals, and adding the incremental line integrals for each composite line integral to form pixels of the DRR image.