1. A computer-implemented method for automatically placing a new dimension annotation of a computer-aided design model representing a real-world object, the method comprising: having a computer-aided design model displayed on a computer screen, the displayed computer-aided design model including various entities; in a processor, receiving user selection of an entity to annotate in the displayed computer-aided design model, said user selection being by a user placing a cursor at the entity as displayed in the computer-aided design model on the computer screen; in response, in the processor, automatically determining at least one location in association with the selected entity in the displayed computer-aided design model for placement of the new dimension annotation based on dimension type of the selected entity, wherein the new dimension annotation is an additional dimension annotation relative to currently existing dimension annotations in the computer-aided design model, and the new dimension annotation is instructive of constructing the real-world object, and wherein the determining includes: creating one or more sets of the currently existing dimension annotations, wherein currently existing dimension annotations of any one or combination of a similar proximity range, a same dimension type, and a same orientation belong to a same set; and sorting the currently existing dimension annotations in the same set and the new dimension annotation having any one or combination of the similar proximity range, the same dimension type, and the same orientation as the currently existing dimension annotations in the same set; rendering the currently existing dimension annotations in the same set and the new dimension annotation on the computer screen in an arrangement, wherein the rendered arrangement of the currently existing dimension annotations in the same set and the new dimension annotation corresponds to an order resulting from the sorting; and displaying a user-interface widget near placement of the cursor as placed at the selected entity, the user-interface widget designating the locations determined for placement of the new dimension annotation, and upon the cursor hovering over the widget, displaying a preview of the rendered arrangement having the new dimension annotation placed in one of the determined locations in the displayed computer-aided design model.