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poly2fv

Convert polygon coordinates to patch faces and vertices

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    Syntax

    [F,V] = poly2fv(x,y)

    Description

    [F,V] = poly2fv(x,y) converts the polygon coordinates defined by x and y into the triangular polygon regions defined by V and F, where V contains the vertices and F determines the vertices to connect.

    You can use the outputs of this function to display polygon regions by using the patch function.

    example

    Examples

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    Open Live Script

    Specify the xy-coordinates of three polygons:

    • A rectangle with vertices in a clockwise order.

    • A square with vertices in a counterclockwise order.

    • A triangle with vertices in a counterclockwise order.

    x1 = [0 0 6 6 0];
y1 = [0 3 3 0 0];
x2 = [1 2 2 1 1];
y2 = [1 1 2 2 1];
x3 = [4 5 4 4];
y3 = [1 1 2 1];

    Convert the coordinates to patch faces and vertices.

    [F,V] = poly2fv({x1,x2,x3},{y1,y2,y3});

    Display the patch.

    figure
patch("Faces",F,"Vertices",V,"FaceColor","r","EdgeColor","none")
axis equal

    Figure contains an axes object. The axes object contains an object of type patch.

    Input Arguments

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    x-coordinates of the polygon, specified as a numeric vector or a cell array of numeric vectors.

    • Define one polygon by specifying a vector, such as [39 45 19 39].

    • Define multiple polygons by using one of these options:

      • Specify a vector and separate the polygons using NaN values, such as [37 46 31 20 37 NaN 45 49 35 32 45 NaN 35 40 42 35]. The NaN values in x must correspond to the NaN values in y.

      • Specify a cell array of vectors, such as {[37 46 31 20 37],[45 49 35 32 45],[35 40 42 35]}. The size of the vector in each cell of x must match the size of the vector in the corresponding cell of y.

    The size and type of x must match the size and type of y.

    y-coordinates of the polygon, specified as a numeric vector or a cell array of numeric vectors.

    • Define one polygon by specifying a vector, such as [-113 -49 -100 -113].

    • Define multiple polygons by using one of these options:

      • Specify a vector and separate the polygons using NaN values, such as [69 90 105 79 69 NaN 6 52 43 14 6 NaN 18 32 22 18]. The NaN values in y must correspond to the NaN values in x.

      • Specify a cell array of vectors, such as {[69 90 105 79 69],[6 52 43 14 6],[18 32 22 18]}. The size of the vector in each cell of y must match the size of the vector in the corresponding cell of x.

    The size and type of y must match the size and type of x.

    Output Arguments

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    Polygon face definitions, returned as a three-column matrix that determines which vertices in V to connect. The poly2fv function creates triangular faces.

    Data Types: double

    Polygon vertices, returned as a two-column matrix. Each row of the matrix contains the xy-coordinates of a vertex.

    Data Types: double

    Tips

    Most Mapping Toolbox™ functions assume that clockwise-ordered vertices define external polygon edges and counterclockwise-ordered vertices define internal polygon edges. Although the poly2fv function ignores vertex order, you can ensure consistency with other functions by following this convention.

    Version History

    Introduced before R2006a

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    See Also

    Functions

    Objects

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