Cylindrical to planar image mapping using scanline coherence

In a computer controlled display system, a method for displaying perspective views of a cylindrical environment map, said cylindrical environment map comprised of a plurality of pixel shading values, said method comprising the steps of:

• a) determining a viewpoint from which to view said cylindrical environment map;
• b) identifying a rotation direction;
• c) if said rotation direction is horizontal, performing the steps of:
• identifying a first portion of said cylindrical environment map to be viewed, said first portion having a plurality of vertical scanlines;
• identifying a first viewing plane;
• scaling said first portion vertically to said viewing plane by generating a first plurality of scaling factors and
• applying the scaling factor corresponding to each of said plurality of vertical scanlines to each of said plurality of vertical scanlines;
• mapping said first viewing plane to a coordinate system associated with a viewing device on which said perspective view will be displayed;
• d) if said rotation direction is vertical, performing the steps of:
• identifying a second portion of said cylindrical
• environment map to be viewed, said second portion having a plurality of scanlines;
• identifying a vertical plane corresponding to said second portion and said vertical rotation;
• scaling said second portion vertically to said vertical plane by generating a second plurality of scaling factors and applying the scaling factor corresponding to each of said plurality of scanlines to each of said plurality of scanlines;
• identifying a second viewing plane;
• scaling said vertical plane horizontally to said second viewing plane;
• mapping said second viewing plane to a coordinate system associated with a viewing device on which said perspective view will be displayed.

A computer controlled display system for generating perspective views of a cylindrical environment map, said system comprising:

• a) first storage means for storing said cylindrical environment map;
• b) second storage means for storing pixel shading values;
• c) a display means for displaying a perspective view, said display means coupled to said second storage means;
• d) means for identifying a portion of said cylindrical environment map to be displayed;
• e) horizontal scaling means coupled to said means for identifying a portion of said cylindrical environment map to be displayed and said second storage means, said horizontal scaling means for generating pixel shading values on a horizontal scanline by determining a plurality of horizontal scaling factors and applying the scaling factor corresponding to a horizontal scanline of said plurality of horizontal scanlines to each pixel shading value in said horizontal scanline;
• and
• f) vertical scaling means coupled to said means for identifying a portion of said cylindrical environment map to be displayed and said second storage means, said vertical scaling means for generating pixel shading values on a vertical scanline by determining a plurality of vertical scaling factors and applying the scaling factor corresponding to a vertical scanline of said plurality of vertical scanlines to each pixel shading value in said vertical scanline.