二次贝塞尔曲线:计算点 [英] Quadratic Bézier Curve: Calculate Points

问题描述

我想计算一个二次曲线上的点.要将其与HTML5的canvas元素一起使用.

I'd like to calculate a point on a quadratic curve. To use it with the canvas element of HTML5.

当我使用 quadraticCurveTo() 函数，我有一个源点，一个目标点和一个控制点.

When I use the quadraticCurveTo() function in JavaScript, I have a source point, a target point and a control point.

我如何在创建的二次曲线上以t=0.5在仅"知道这三个点的情况下计算一个点?

How can I calculate a point on the created quadratic curve at let's say t=0.5 with "only" knowing this three points?

推荐答案

使用二次Bézier公式，例如在Wikipedia页面上找到的

Use the quadratic Bézier formula, found, for instance, on the Wikipedia page for Bézier Curves:

在伪代码中，那是

t = 0.5; // given example value
x = (1 - t) * (1 - t) * p[0].x + 2 * (1 - t) * t * p[1].x + t * t * p[2].x;
y = (1 - t) * (1 - t) * p[0].y + 2 * (1 - t) * t * p[1].y + t * t * p[2].y;

p[0]是起点，p[1]是控制点，p[2]是终点. t是参数，从0到1.

p[0] is the start point, p[1] is the control point, and p[2] is the end point. t is the parameter, which goes from 0 to 1.

这篇关于二次贝塞尔曲线:计算点的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！