Function createPolygon

src/offset-polygon.ts:56–99

(vertices: Vector[])

}

function createPolygon(vertices: Vector[]): Polygon {
  const edges: Edge[] = [];
  let minX = vertices.length > 0 ? vertices[0].x : undefined;
  let minY = vertices.length > 0 ? vertices[0].y : undefined;
  let maxX = minX;
  let maxY = minY;

  for (let i = 0; i < vertices.length; i++) {
    const vertex1 = vertices[i];
    const vertex2 = vertices[(i + 1) % vertices.length];

    const outwardNormal = outwardEdgeNormal(vertex1, vertex2);

    const inwardNormal = inwardEdgeNormal(vertex1, vertex2);

    const edge: Edge = {
      vertex1,
      vertex2,
      index: i,
      outwardNormal,
      inwardNormal,
    };

    edges.push(edge);

    const x = vertices[i].x;
    const y = vertices[i].y;
    minX = Math.min(x, minX);
    minY = Math.min(y, minY);
    maxX = Math.max(x, maxX);
    maxY = Math.max(y, maxY);
  }

  const polygon: Polygon = {
    vertices,
    edges,
    minX,
    minY,
    maxX,
    maxY,
  };

  return polygon;
}

// based on http://local.wasp.uwa.edu.au/~pbourke/geometry/lineline2d/, edgeA => "line a", edgeB => "line b"