这篇文章主要介绍多段线实现布尔运算的方法
先上代码
function getOperatedCurves(sourceCurs: Curve[], targetCus: Curve[]) { let source: Polyline | Circle = (sourceCurs[0] instanceof Circle) ? sourceCurs[0] as Circle : new Polyline().Combine(sourceCurs)[0]; let target: Polyline | Circle = (targetCus[0] instanceof Circle) ? targetCus[0] as Circle : new Polyline().Combine(targetCus)[0]; try { if (!source.IsClose || !target.IsClose) throw new Error("不是封闭曲线"); } catch (err) { console.log(err); } let interPts = source.IntersectWith(target, IntersectOption.OnBothOperands); let sourceContainerTarget = isTargetCurInSourceCur(source, target); let targetContainerSource = isTargetCurInSourceCur(target, source); let isContainer = sourceContainerTarget || targetContainerSource; let intersectionList: Curve[] = []; //交集 let unionList: Curve[] = []; //并集 let subList: Curve[] = []; //补集 /* *两封闭区域有交点并且不是包含关系,则通过交点把区域分割 */ if (interPts.length && !isContainer) { let pars1 = interPts.map(p => source.GetParamAtPoint(p)).sort((a, b) => a - b); let pars2 = interPts.map(p => target.GetParamAtPoint(p)).sort((a, b) => a - b); let cus1: Array<Polyline | Arc> = source.GetSplitCurves(pars1); cus1.forEach(pl => { if (isTargetCurInSourceCur(target, pl)) { intersectionList.push(pl); } else { subList.push(pl); unionList.push(pl); } }) let cus2: Array<Polyline | Arc> = target.GetSplitCurves(pars2); cus2.forEach(pl => { if (isTargetCurInSourceCur(source, pl)) { intersectionList.push(pl); subList.push(pl); } else { unionList.push(pl); } }) } else { if (isContainer) { if (sourceContainerTarget) { intersectionList.push(target); subList.push(source, target); unionList.push(source); } else { unionList.push(target); intersectionList.push(source); } } else { unionList.push(source, target) subList.push(source); } } return { intersectionList, unionList, subList } }
由于一些曲线类实现方法不一，这里主要说一些实现布尔运算的思路
判断2封闭曲线是否是被包含的关系
获取2封闭曲线的所有交点，这里交点可能是圆和线，线和线，圆和圆的，求交点的方法网上应该很多，以后有时间也会写写用JavaScript实现方式
根据所有的交点把2封闭曲线分割为多个部分
对分割后的线段进行整理，其中相交部分是曲线在对方曲线内部的部分，合并是互不在对方曲线内部的部分，相减类似不想说了，具体看代码，如果是被包含状态则更加就简单了