poly_poly_clip

poly_poly_clip calculates the intersections between a polygon (open polygon) and a data hull (closed polygon).

<rmXY, idx> = poly_poly_clip(nOpt, clip, poly)

Return Value

rmXY, idx: rmXY is a matrix with two columns. The first column contains the x-coordinates and the second column the y-coordinates of the result polygon. idx is an index vector with the end points of the polygons (see example).

Parameters

nOpt

nOpt specifies what result should be computed. nOpt can be one of the following values:

Value	Meaning
0	union (hull containing both polygons).
1	difference (part of the subject polygon that is inside the clip hull).
2	difference (part of the subject polygon that is inside the clip hull).
3	hull without subject polygon.

clip

clip are the x/y-coordinates of the clip polygon. The coordinates must be given as a complex vector (x + 1i*y) (see example).

poly

poly are the x/y-coordinates of the subject polygon. The coordinates must be given as a complex vector (x + 1i*y) (see example).

Example

def test(option)
{
    xhull = [1, 1, 2, 2, 1];
    yhull = [1, 2, 2, 1, 1];
    nh = len(xhull)
    h = plot(xhull,yhull)
    xp = [1.3, 1.3, 1.6, 1.6, 1.3];
    yp = [0.3, 2.6, 2.6, 0.3, 0.3];
    <xy, idx> = poly_poly_clip(option, xhull[1:nh] + 1i * yhull[1:nh], xp + 1i*yp);
    if (len(idx) == 1 && idx[1] == 0) {
        return TRUE;
    }
    nPoly = len(idx);
    if (len(xy) > 1) {
        idx = [0;idx];
        for (i in 2:nPoly+1) {
            h = plot(xy[idx[i-1]+1:idx[i]; 1], xy[idx[i-1]+1:idx[i];2], h[2]);
        }
    }
    return xy;
}

See also

poly_line_clip, poly_hull

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