通过点击vtk的renderWindow，获取坐标点。

获取点的坐标有vtkCellPicker和vtkPointPicker两个方法，区别在于vtkCellPicker可以区分是否点击在模型上，推荐使用vtkCellPicker。
获取两点之间距离使用vtkMath的方法，vtkMath.distance2BetweenPoints(point1, point2), 结果需要开平方。

// 初始化vtk
import vtkFullScreenRenderWindow from '@kitware/vtk.js/Rendering/Misc/FullScreenRenderWindow'

const div = this.$refs.modelBox
const fullScreenRenderer = vtkFullScreenRenderWindow.newInstance({
  container: div,
  background: [0, 0, 0]
})
this.renderer = fullScreenRenderer.getRenderer()
this.renderWindow = fullScreenRenderer.getRenderWindow()
this.renderWindow.getInteractor().render()

import vtkInteractorStyleImage from '@kitware/vtk.js/Interaction/Style/InteractorStyleImage'

// 设置可点击
const interactorStyle = vtkInteractorStyleImage.newInstance()
this.renderWindow.getInteractor().setInteractorStyle(interactorStyle)
const mainInteractor = this.renderWindow.getInteractor()
// 鼠标左键点击
mainInteractor.onLeftButtonPress((callData) => {
  if (this.renderer !== callData.pokedRenderer) {
    return
  }
})

获取在模型上点击的点(vtkCellPicker)

import vtkCellPicker from '@kitware/vtk.js/Rendering/Core/CellPicker'

mainInteractor.onLeftButtonPress((callData) => {
	if (this.renderer !== callData.pokedRenderer) {
	  return
	}
	const pos = callData.position
	const screenPoint = [pos.x, pos.y, pos.z]
	const actor = ... // 模型
	const picker = vtkCellPicker.newInstance()
	picker.setPickFromList(1)
	picker.setTolerance(0)
	picker.initializePickList()
	picker.addPickList(actor)
	picker.pick(screenPoint, this.renderer)
	if (picker.getActors().length > 0) { // 在模型上点击
	  const pickedPoints = picker.getPickedPositions()[0]
	  // 获取模型当前点击的世界坐标
	  console.log(pickedPoints)
	} else { // 在模型外点击
		const pickedPoint = picker.getPickPosition()
	    // 获取模型当前点击的世界坐标
	    console.log(pickedPoint)
	}
})

获取点击vtkJs renderWindow的点(vtkPointPicker)

import vtkPointPicker from '@kitware/vtk.js/Rendering/Core/PointPicker'

mainInteractor.onLeftButtonPress((callData) => {
	if (this.renderer !== callData.pokedRenderer) {
	  return
	}
	const pointPicker = vtkPointPicker.newInstance()
    pointPicker.pick(screenPoint, this.renderer)
    const pickedPoints = pointPicker.getPickPosition()
    console.log(pickedPoints) // 点击的点世界坐标
})

获取两点之间的距离

import * as vtkMath from '@kitware/vtk.js/Common/Core/Math'

// point1、point2可通过点击获取
const point1 = [...] // 起始点（世界坐标）
const point2 = [...] // 结束点（世界坐标）
const pointLen = vtkMath.distance2BetweenPoints(point1, point2)

const distance = Math.sqrt(pointLen)
console.log(`两点之间的距离：${distance}mm`)