Context-preserving display system using a perspective sheet

A method for presenting an interactive navigation of an image where context and detail information are preserved even when the image contains too much detail to be displayed all at once on a display surface, the method comprising the steps of:

• a) defining a display extent on the display surface within which extent the image is to be displayed;
• b) defining a 3-D space and a viewpoint in the 3-D space;
• c) accepting user input to determine an extent and a position of a focus panel in the 3-D space wherein said focus panel is a panel positioned within boundaries of a representation of the display surface;
• d) calculating a transform matrix for each of said focus panel, four edge panels and four corner panels, wherein an edge panel is a rectangle in the 3-D space with one edge coincident with the focus panel and an opposite edge coincident with an edge of the display extent and wherein a corner panel is a parallelogram in the 3-D space with two adjacent edges coincident with edges of two edge panels, thereby forming a continuous, nine-panel surface in the 3-D space with a transformation matrix for a panel defining a mapping of points on the image to points on the nine-panel surface;
• wherein calculating the transform matrix for each of said four corner panels comprises the steps of:
• (1) calculating a shearing transform of a corner panel from a rectangle to a quadrilateral, said shearing transform resulting in an angle between side edges of said corner panel equal to a fitting angle for said quadrilateral, wherein said fitting angle is an angle formed by edges of the two side panels adjacent to the corner panel for which the shearing transform is calculated;
• and
• (2) calculating a rotation transform of the quadrilateral in said layout plane, the rotation transform being a transform of a rotation by a rotation angle which would rotate the quadrilateral into alignment with the two side panels;
• e) rendering a display image of the continuous, nine-panel surface from the viewpoint using the transformation matrices calculated in step d), the step of rendering using as its input a plurality of object representations providing the context and detail information;
• and
• f) repeating at least steps c), d) and e) in real-time to provide interactive navigation of the image by a user inputting the user input.