Importance

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Abstract

A method for removing hidden lines in a two-dimensional surface chart disclosing an image of a three-dimensional surface, includes storing the X, Y and Z co-ordinates of selected points (A, B, C, D, E) of the surface as a first matrix, transforming the first matrix into a second matrix indicating the drawing sequence through the selected points, rotating the points of the second matrix around the Z-axis a first angle .alpha., rotating the second matrix points a second angle .beta. and drawing the two-dimensional surface chart in accordance with the indicated sequence using the X and Y co-ordinate values of the rotated points. The drawing sequence comprises a drawing operation of X-traces, an X-trace being defined as a line passing through points having substantially the same Y values in the first matrix, the drawing operation of one X-trace being followed by a plurality of .DELTA. Y -trace drawing operations between the last drawn X-trace and the next to be drawn X-trace, an Y-trace being defined as a line passing through points having substantially the same X values in the first matrix and a .DELTA.Y-trace being defined as the part of an Y-trace falling between two adjacent X-traces, said sequential drawing operation proceeding in sequence from low Y value X-traces toward high value X-traces. No lines are drawn inside a forbidden area being defined as an area surrounded by an upper horizon and a lower horizon.

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First Claim