ve 15-bit integer range x = ( x - minX ) * invSize | 0; y = ( y - minY ) * invSize | 0; x = ( x | ( x << 8 ) ) & 0x00FF00FF; x = ( x | ( x << 4 ) ) & 0x0F0F0F0F; x = ( x | ( x << 2 ) ) & 0x33333333; x = ( x | ( x << 1 ) ) & 0x55555555; y = ( y | ( y << 8 ) ) & 0x00FF00FF; y = ( y | ( y << 4 ) ) & 0x0F0F0F0F; y = ( y | ( y << 2 ) ) & 0x33333333; y = ( y | ( y << 1 ) ) & 0x55555555; return x | ( y << 1 ); } // find the leftmost node of a polygon ring function getLeftmost( start ) { let p = start, leftmost = start; do { if ( p.x < leftmost.x || ( p.x === leftmost.x && p.y < leftmost.y ) ) leftmost = p; p = p.next; } while ( p !== start ); return leftmost; } // check if a point lies within a convex triangle function pointInTriangle( ax, ay, bx, by, cx, cy, px, py ) { return ( cx - px ) * ( ay - py ) >= ( ax - px ) * ( cy - py ) && ( ax - px ) * ( by - py ) >= ( bx - px ) * ( ay - py ) && ( bx - px ) * ( cy - py ) >= ( cx - px ) * ( by - py ); } // check if a diagonal between two polygon nodes is valid (lies in polygon interior) function isValidDiagonal( a, b ) { return a.next.i !== b.i && a.prev.i !== b.i && ! intersectsPolygon( a, b ) && // dones't intersect other edges ( locallyInside( a, b ) && locallyInside( b, a ) && middleInside( a, b ) && // locally visible ( area( a.prev, a, b.prev ) || area( a, b.prev, b ) ) || // does not create opposite-facing sectors equals( a, b ) && area( a.prev, a, a.next ) > 0 && area( b.prev, b, b.next ) > 0 ); // special zero-length case } // signed area of a triangle function area( p, q, r ) { return ( q.y - p.y ) * ( r.x - q.x ) - ( q.x - p.x ) * ( r.y - q.y ); } // check if two points are equal function equals( p1, p2 ) { return p1.x === p2.x && p1.y === p2.y; } // check if two segments intersect function intersects( p1, q1, p2, q2 ) { const o1 = sign( area( p1, q1, p2 ) ); const o2 = sign( area( p1, q1, q2 ) ); const o3 = sign( area( p2, q2, p1 ) ); const o4 = sign( area( p2, q2, q1 ) ); if ( o1 !== o2 && o3 !== o4 ) return true; // general case if ( o1 === 0 && onSegment( p1, p2, q1 ) ) return true; // p1, q1 and p2 are collinear and p2 lies on p1q1 if ( o2 === 0 && onSegment( p1, q2, q1 ) ) return true; // p1, q1 and q2 are collinear and q2 lies on p1q1 if ( o3 === 0 && onSegment( p2, p1, q2 ) ) return true; // p2, q2 and p1 are collinear and p1 lies on p2q2 if ( o4 === 0 && onSegment( p2, q1, q2 ) ) return true; // p2, q2 and q1 are collinear and q1 lies on p2q2 return false; } // for collinear points p, q, r, check if point q lies on segment pr function onSegment( p, q, r ) { return q.x <= Math.max( p.x, r.x ) && q.x >= Math.min( p.x, r.x ) && q.y <= Math.max( p.y, r.y ) && q.y >= Math.min( p.y, r.y ); } function sign( num ) { return num > 0 ? 1 : num < 0 ? - 1 : 0; } // check if a polygon diagonal intersects any polygon segments function intersectsPolygon( a, b ) { let p = a; do { if ( p.i !== a.i && p.next.i !== a.i && p.i !== b.i && p.next.i !== b.i && intersects( p, p.next, a, b ) ) return true; p = p.next; } while ( p !== a ); return false; } // check if a polygon diagonal is locally inside the polygon function locallyInside( a, b ) { return area( a.prev, a, a.next ) < 0 ? area( a, b, a.next ) >= 0 && area( a, a.prev, b ) >= 0 : area( a, b, a.prev ) < 0 || area( a, a.next, b ) < 0; } // check if the middle point of a polygon diagonal is inside the polygon function middleInside( a, b ) { let p = a, inside = false; const px = ( a.x + b.x ) / 2, py = ( a.y + b.y ) / 2; do { if ( ( ( p.y > py ) !== ( p.next.y > py ) ) && p.next.y !== p.y && ( px < ( p.next.x - p.x ) * ( py - p.y ) / ( p.next.y - p.y ) + p.x ) ) inside = ! inside; p = p.next; } while ( p !== a ); return inside; } // link two polygon vertices with a bridge; if the vertices belong to the same ring, it splits polygon into two; // if one belongs to the outer ring and another to a hole, it merges it into a single ring function splitPolygon( a, b ) { const a2 = new Node( a.i, a.x, a.y ), b2 = new Node( b.i, b.x, b.y ), an = a.next, bp = b.prev; a.next = b; b.prev = a; a2.next = an; an.prev = a2; b2.next = a2; a2.prev = b2; bp.next = b2; b2.prev = bp; return b2; } // create a node and optionally link it with previous one (in a circular doubly linked list) function insertNode( i, x, y, last ) { const p = new Node( i, x, y ); if ( ! last ) { p.prev = p; p.next = p; } else { p.next = last.next; p.prev = last; last.next.prev = p; last.next = p; } return p; } function removeNode( p ) { p.next.prev = p.prev; p.prev.next = p.next; if ( p.prevZ ) p.prevZ.nextZ = p.nextZ; if ( p.nextZ ) p.nextZ.prevZ = p.prevZ; } function Node( i, x, y ) { // vertex index in coordinates array this.i = i; // vertex coordinates this.x = x; this.y = y; // previo