在 d3.js 中查找路径的切线 [英] Find tangent of path in d3.js

问题描述

我想沿路径放置 svg 元素(例如椭圆)，例如使用 d3.js 生成的曲线 带 B 样条插值的线生成器.虽然使用 path.getPointAtLength() 可以轻松找到沿路径点的坐标，但我无法弄清楚如何找到线上任何点的切线.如果我能得到切线(或导数)，我就可以相应地旋转元素，使它们看起来好像沿着线定位.

I'd like to position svg elements (say, ellipses) along a path, for instance a curve generated with a d3.js line generator with B-spline interpolation. While finding the coordinates of points along the path is easy using path.getPointAtLength(), I can't figure out how to find the tangent of any point on the line. If I could get the tangent (or the derivative), I would be able to rotate the elements accordingly to make them look as if they are positioned along the line.

推荐答案

在靠近的两个点调用 path.getPointAtLength().微积分告诉我们区别在于那个点的斜率/切线.

Call path.getPointAtLength() at two points close together. Calculus tells us the difference is the slope/tangent at that point.

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