A real-time three-dimensional display device particularly suited for medical imaging is disclosed. The device includes a plurality of individual processing elements each having an image memory for storing a mini-image of a portion of the object as viewed from any given direction and a merge control means for generating a combined image of the object including the depth thereof by selection on a pixel-by-pixel basis from each of the mini-images. In two different embodiments, priority codes are assigned to each of the processing elements reflecting the relative significance of a given pixel of the mini-image produced by a given processing element as compared to the pixels of mini-images produced by other processing elements. In one embodiment, the combined image is generated in accordance with the priority codes. In another embodiment, a Z buffer is used to provide for hidden surface removal on a pixel-by-pixel basis. Improved shadow, shading and gradient processors are provided to provide three-dimensional imaging as well as an improved scan conversion means for generating a coherent image from the combined images merged from all of the processing elements.