1. A method comprising: outputting to a display a first 2-D image rendered from a 3-D model of a 3-D object in a 3-D model space wherein points defining the 3-D model are at first 3-D locations in the 3-D model space when the first 2-D image is rendered; after the first 2-D image is output to the display, receiving a sequence of navigational inputs from at least one input source wherein the sequence of navigational inputs begins with a first navigational input; selecting a second navigational input from among the sequence of navigational inputs; based upon at least the second navigational input, determining second 3-D locations of the points defining the 3-D model in the 3-D model space; based upon the second 3-D locations, outputting to the display a second 2-D image rendered from the 3-D model in the 3-D model space; based upon one of i) a first change between the first navigational input and the second navigational input, ii) a second change between the first 3-D locations and the second 3-D locations or iii) combinations thereof, determining whether to increment a count; incrementing the count; after the count is incremented, determining the count exceeds a threshold value; in response to the count exceeding the threshold value, unlocking a second 3-D model of a second 3-D object; determining first 3-D locations of points defining the second 3-D model of the second 3-D object in the 3-D model space; and based upon the first 3-D locations of the points defining the second 3-D model, outputting to the display a third 2-D image rendered from the second 3-D model in the 3-D model space.