Function isNestedRingClosed

docs/app/js/sanddance-app.js:103685–103689

(simplePolygon)

    return polygon.length >= 1 && polygon[0].length >= 2 && Number.isFinite(polygon[0][0]);
}
function isNestedRingClosed(simplePolygon) {
    var p0 = simplePolygon[0];
    var p1 = simplePolygon[simplePolygon.length - 1];
    return p0[0] === p1[0] && p0[1] === p1[1] && p0[2] === p1[2];
}
function isFlatRingClosed(positions, size, startIndex, endIndex) {
    for(var i = 0; i < size; i++){
        if (positions[startIndex + i] !== positions[endIndex - size + i]) return false;