Function cutPolygonByGrid

docs/app/js/sanddance-app.js:102311–102371

(positions, holeIndices = null, options)

    return arr1;
}
function cutPolygonByGrid(positions, holeIndices = null, options) {
    if (!positions.length) return [];
    const { size =2 , gridResolution =10 , gridOffset =[
        0,
        0
    ] , edgeTypes =false  } = options || {};
    const result = [];
    const queue = [
        {
            pos: positions,
            types: edgeTypes ? new Array(positions.length / size).fill(TYPE_BORDER) : null,
            holes: holeIndices || []
        }
    ];
    const bbox = [
        [],
        []
    ];
    let cell = [];
    while(queue.length){
        const { pos , types , holes  } = queue.shift();
        getBoundingBox(pos, size, holes[0] || pos.length, bbox);
        cell = getGridCell(bbox[0], gridResolution, gridOffset, cell);
        const code = (0, _lineclip.bitCode)(bbox[1], cell);
        if (code) {
            let parts = bisectPolygon(pos, types, size, 0, holes[0] || pos.length, cell, code);
            const polygonLow = {
                pos: parts[0].pos,
                types: parts[0].types,
                holes: []
            };
            const polygonHigh = {
                pos: parts[1].pos,
                types: parts[1].types,
                holes: []
            };
            queue.push(polygonLow, polygonHigh);
            for(let i = 0; i < holes.length; i++){
                parts = bisectPolygon(pos, types, size, holes[i], holes[i + 1] || pos.length, cell, code);
                if (parts[0]) {
                    polygonLow.holes.push(polygonLow.pos.length);
                    polygonLow.pos = concatInPlace(polygonLow.pos, parts[0].pos);
                    if (edgeTypes) polygonLow.types = concatInPlace(polygonLow.types, parts[0].types);
                }
                if (parts[1]) {
                    polygonHigh.holes.push(polygonHigh.pos.length);
                    polygonHigh.pos = concatInPlace(polygonHigh.pos, parts[1].pos);
                    if (edgeTypes) polygonHigh.types = concatInPlace(polygonHigh.types, parts[1].types);
                }
            }
        } else {
            const polygon = {
                positions: pos
            };
            if (edgeTypes) polygon.edgeTypes = types;
            if (holes.length) polygon.holeIndices = holes;
            result.push(polygon);
        }