This paper considers 3D imaging of moving objects and introduces a technique that exploits visible and x-ray images to recover dense 3D models. While recent methods such as tomography from cone-beam x-ray can advantageously replace more expensive and higher-dose CT scanners, they still require specific equipment and immobilised patients. We investigate an alternative strategy that combines a single x-ray source and a set of colour cameras to capture rigidly moving samples. The colour cameras allow for coarse marklerless motion tracking, which is further refined with the x-ray information. Once the sample poses are correctly estimated, a dense 3D attenuation model is reconstructed from the set of x-ray frames. Preliminary results on simulated data compared to ground-truth as well as actual in-vivo experiments are presented.