创建三角形UIRegions

Question

我需要将屏幕分成如下所示的区域（用黑线分隔）：

文档说Most regions are rectangular or elliptical in shape, but you can use the methods of this class to create more complex shapes by adding, subtracting, and intersecting other regions.我无法弄清楚如何创建它们。

对于上下文，我试图复制StickyCorners: Using UIFieldBehavior and other UIDynamicBehaviors演示，但添加4个粘性点，每个中点1个（用红色圆圈表示）。