As you see in Figure 4, The solution to the point-in-polygon problem is to draw a horizontal line starting at the point in question.
如图 4 中所示，点包容问题的解决方案是绘制一条从所关注的点开始的水平线。
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Each point of the polygon is added to the temporary shape on line 23, and if it's the first point in the polygon, its location is recorded as the placement for the text annotating that piece.
First it shows the finished hand rotating in 3d space, then explains how the computer built the image using polygon points placed on Catmull's left hand.