Systems and methods for annotating pages of a 3D electronic document

摘要: To annotate a three-dimensional electronic object, eg, docu ment, a user specifies, on a two-dimensional Screen, a portion of a page of a three-dimensional document as a specified page area to be annotated by making a stroke. The annotation may be displayed to the user by a hybrid technique where the annotation is displayed by a 3D polyline segment placed behind the near clipping plane of a virtual camera frustrum. At the same time, previous annotations are displayed by another technique, such as, for example, the texture coloring technique. During the intermittent time between the stroke and another stroke the 3D polyline segment is removed from behind the near clipping plane and the page texture is updated with the annotation data. The display techniques Support highlighting annotations, free-form annotations, and text annotations.