1. A three dimensional (3D) drawing method for immersing a user in an interactive 3D experience, comprising: in response to first signals from a controller, projecting a 3D image of the user on a projection screen; with a position tracking mechanism, determining 3D positions of a drawing instrument positionable by the user, during a drawing time period, relative to the 3D image and proximate but spaced apart from the projection screen; storing the set of determined 3D positions in memory accessible by a controller; with the controller, generating a 3D drawing image based on the set of determined 3D positions; in response to second signals from the controller, projecting a mixed 3D image, on the projection screen, that comprises a blending of the projected 3D image of the user and the 3D drawing image, wherein the projected 3D image of the user comprises a first set of left and right eye images and wherein the projected mixed 3D image comprises a second set of left and right eye images differing from the first set of left and right images; wherein the projecting of the mixed 3D image is performed concurrently with the tracking of the 3D positions of the drawing instrument; wherein the determining of 3D positions is performed only after the controller receives a start drawing signal from the drawing instrument and is terminated after the controller receives a stop drawing signal from the drawing instrument, whereby the user selectively starts and stops 3D drawing with the drawing instrument; wherein the method further comprises capturing the 3D image of the user and wherein the projected 3D image of the user is mixed with a 3D background image; wherein the capturing of the 3D image of the user includes capturing a left eye image with a first camera and a right eye image with a second camera spaced apart from the first camera by an interocular distance and further includes processing the left and right eye images to key out an image of the user from background images; and wherein the projecting of the 3D image of the user mixed with the 3D background image comprises projecting with one projector or with two projectors the processed left eye images with left eye images of the 3D background image and the processed right eye images with right eye images of the 3D background image.