How to creat a plane according 2 points

Community
1

Dear friends

I know there are many ways in slicer to creat a plane

Then how to use two points to create a plane that passes through the middle point of these two points and is perpendicular to the line formed by the two points?

any way or script will be useful!

thankyou!

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2

It should be doable with vtkMath::Perpendiculars() with a direction vector relative to the middle point.

Calculate

  • the middle point,
  • a direction vector with either point relative to the middle point,
  • the perpendiculars at the middle point using the direction vector.

By adding the perpendiculars to the middle point, you have the 3 points of a plane.

3

I would really appreciate it if you could help me write this slicer script

4

This should work when pasted in the Python console.

Add a fiducial node named ‘F’ with 2 points, and a plane named ‘P’ before.

def findMiddleCrossSectionPlane(p1, p2):
    middlePoint = ((p1[0] + p2[0]) / 2.0, (p1[1] + p2[1]) / 2.0, (p1[2] + p2[2]) / 2.0)
    directionVector = [0.0, 0.0, 0.0]
    vtk.vtkMath().Subtract(p2, middlePoint, directionVector)
    
    perpendicular1 = [0.0, 0.0, 0.0]
    perpendicular2 = [0.0, 0.0, 0.0]
    vtk.vtkMath().Perpendiculars(directionVector, perpendicular1, perpendicular2, 0.0)
    
    planePoint1 = [0.0, 0.0, 0.0]
    planePoint2 = [0.0, 0.0, 0.0]
    vtk.vtkMath().Add(middlePoint, perpendicular1, planePoint1)
    vtk.vtkMath().Add(middlePoint, perpendicular2, planePoint2)
    
    return (middlePoint, planePoint1, planePoint2)
    

# Add a fiducial node named 'F', and a plane named 'P'
f = slicer.util.getNode("F")
p1 = [0.0, 0.0, 0.0]
p2 = [0.0, 0.0, 0.0]
f.GetNthControlPointPositionWorld(0, p1)
f.GetNthControlPointPositionWorld(1, p2)

planePoints = findMiddleCrossSectionPlane(p1, p2)

# Just for visualisation.
plane = slicer.util.getNode("P")
plane.SetPlaneType(slicer.vtkMRMLMarkupsPlaneNode.PlaneType3Points)
plane.SetNthControlPointPositionWorld(0, planePoints[0])
plane.SetNthControlPointPositionWorld(1, planePoints[1])
plane.SetNthControlPointPositionWorld(2, planePoints[2])
5

thankyou very much! it works well!

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6

Sorry to disturbe you,Mr！

In the last version slicer，the script does not work.

It shows the errors.

Would you like to help solve the problem?

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7

Hi, I checked with 5.3.0-2023-07-23 r31895 / 98f1a5a on Linux and the script does work.

The error messages mean that the plane P is found but does not have any control point. I could reproduce the errors by adding a plane without any control point to the scene. Use one that you can see and interact with normally.

8

can you give me a script about creating a plane through point N and perpendicular to P1,thank you very much.

9

The plane node has a mode where you can define the plane with a point and a normal, see PlaneTypePointNormal
https://apidocs.slicer.org/main/classvtkMRMLMarkupsPlaneNode.html#af83a7dac83b04668a4f2bae10245a7baa5bce04cda74677cd6404657aa0868783

10

I’m really sorry, but I can’t understand that code and I’m not sure which part of the text I should copy. Could you please provide me with the specific text that I can copy directly? Thank you so much!

11

I asked Copilot this question:
“Write me a brief code snippet that creates a vtkMRMLMarkupsPlaneNode from a point and a normal vector using the PlaneTypePointNormal mode.”

It gave me the answer in a few seconds. It looks correct:

import slicer
import numpy as np

# Define the point and normal vector
point = np.array([10.0, 20.0, 30.0])
normal = np.array([0.0, 0.0, 1.0])

# Create a new vtkMRMLMarkupsPlaneNode
planeNode = slicer.mrmlScene.AddNewNodeByClass('vtkMRMLMarkupsPlaneNode')
planeNode.SetName('PlaneNode')

# Set the plane type to PlaneTypePointNormal
planeNode.SetPlaneType(slicer.vtkMRMLMarkupsPlaneNode.PlaneTypePointNormal)

# Set the point and normal vector
planeNode.SetOrigin(point)
planeNode.SetNormal(normal)
1 Like
12

thank you very much :rose: