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cutPolygonByGrid

From-v3.2

Subdivides a polygon by intersecting with a uniform grid.

import {cutPolygonByGrid} from '@math.gl/polygon';

cutPolygonByGrid([0, 15, 15, 0, 0, -15, 0, 15], {size: 2, gridResolution: 20});
// returns [
//   [15, 0, 0, -15, 0, 0, 15, 0],
//   [15, 0, 0, 0, 0, 15, 15, 0]
// ]
]

Usage​

cutPolygonByGrid(positions, holeIndices, [options]);

Arguments:

  • positions (Array|TypedArray) - a flat array of the vertex positions that define the polygon's rings.
  • holeIndices (Array|TypedArray|null) - the indices in positions where each hole starts. If null, the polygon has no holes.
  • options (Object, optional)
    • size (Number) - the number of elements in each vertex. Size 2 will interpret positions as [x0, y0, x1, y1, ...] and size 3 will interpret positions as [x0, y0, z0, x1, y1, z1, ...]. Default 2.
    • gridResolution (Number, optional) - the grid size. Default 10.
    • gridOffset (Array, optional) - the grid offset in [x, y]. Default [0, 0] i.e. the grid starts from the coordinate origin.
    • edgeTypes (Boolean) - if true, returns an additional array for each polygon that describes the nature of each vertex. See "returns" below.

Returns:

An array of polygons. Each polygons is represented by an object with the following fields:

  • positions (Array|TypedArray) - a flat array of the vertex positions that define the polygon's rings.

  • holeIndices (Array|TypedArray) - the indices in positions where each hole starts. Not present if the polygon has no holes.

  • edgeTypes (Array) - describes the nature of each vertex in positions:

    • 0 - the segment connecting this vertex to the next is inside the original polygon
    • 1 - the segment connecting this vertex to the next is on the border of the original polygon