1. A computer-implemented method comprising: providing a 3-D drawing based on 2-D images of a scene taken from multiple different views, wherein the 3-D drawing has a plurality of 3-D drawing primitives; permitting the 3-D drawing primitives to be drawn on a computer screen overlaid on the 2-D images; using a computer, allowing a user to manipulate a 3-D drawing primitive in a view-locked mode, wherein in the view-locked mode, altering of an appearance of the 3-D drawing primitive occurs without changing its appearance on a selected input image; allowing the user to move the 3-D drawing primitive in 3-D under a locked constraint to match its appearance to corresponding features on other 2-D images; allowing view-locking of the 3-D drawing primitive on one 2-D image while aligning on the another 2-D image; and allowing moving of the 3-D drawing primitive on a 3-D plane parallel to a current viewing camera to match its appearance to the corresponding features on other images.