1. A device for 3D-originated cardiac roadmapping, comprising: a processor configured to receive 3D+t image data of a vascular structure of an object; and to receive 2D image data of the object, the 2D image data comprising at least one 2D image; and a display; wherein the processor is further configured to project the vascular structure, thereby generating a plurality of mask images based on the 3D+t image data; perform a registration of the at least one 2D image with one of the plurality of the mask images by finding a maximum of a similarity factor between the plurality of mask images and the at least one 2D image; and generate, according to the registration, a combination of the at least one 2D image and a projection of the vascular structure based on the 3D+t image data; wherein the display is configured to display the combination as a guiding vessel tree projection, wherein an element is located inside a vessel of the vascular structure, wherein the element is visible in the 2D image data, and wherein the display is further configured to display the combination as the guiding vessel tree projection having sub-branches, wherein sub-branches of the sub-branches that do not include the element are attenuated based on a distance from the element for greater fading as the distance increases.