问使用PaperJS我在PaperJS中有一个切点和一个法点-我如何计算所需的点(见下图)

EN

var normal = this.strecke.getNormalAt(offset)

    var normalOffset = normal.multiply(Math.random() * (this.bubbleOffsetX -  (-1)*this.bubbleOffsetX + 1) + (-1)*this.bubbleOffsetX)
    var tanOffset = tangent.multiply(this.bubbleOffsetY)

    var bubblePosition = normalOffset.add(tanOffset).add(point)

    var bubble = new Path.Circle({
      center: bubblePosition,
      radius: Math.floor(Math.random() * (this.bubbleMaxSize - this.bubbleMinSize + 1) + this.bubbleMinSize),
      fillColor: '#A4F2FB',
      opacity: Math.random > 50 ? .5 : .3,
    })

    setTimeout(() => {
      bubble.remove()
    }, this.bubbleLifespan);