I have a helper script that might be helpful.
################# Create points at 4, 7, 10mm
import numpy as np
Given points
P0 = np.array([-95.807, 86.787, -0.063])
P1 = np.array([-96.027, 87.707, -4.015])
Direction vector
v = P1 - P0
Normalize
v_hat = v / np.linalg.norm(v)
Distances you want (mm)
distances = [4, 7, 10]
print("Unit direction vector:", v_hat, "\n")
for d in distances:
P = P0 + d * v_hat
print(f"Point at {d} mm:", P)
#####Create horizontal planes at 4, 7, 10mm
def createPlanes(f, plane2Center=None, angle=None, useBinormal=True,
plane1Name="Plane1", plane2Name="Plane_7mm"):
"""
f: vtkMRMLMarkupsFiducialNode (or any markups node with >=3 control points)
plane2Center: [x,y,z] world coords where plane2 passes through (default: p1)
angle: rotation (degrees) to spin perpendicular choice around plane1 normal (default: 0)
useBinormal: True -> use binormal as plane2 normal, False -> use tangent
"""
# --- Read 3 points from markups node f ---
p1 = [0.0, 0.0, 0.0]
p2 = [0.0, 0.0, 0.0]
p3 = [0.0, 0.0, 0.0]
f.GetNthControlPointPositionWorld(0, p1)
f.GetNthControlPointPositionWorld(1, p2)
f.GetNthControlPointPositionWorld(2, p3)
rotationOfPerpendiculars = float(angle) if angle is not None else 0.0
plane2Coordinates = plane2Center if plane2Center is not None else p1
# --- Create Plane1 (3-point plane) ---
plane1 = slicer.mrmlScene.AddNewNodeByClass("vtkMRMLMarkupsPlaneNode", plane1Name)
plane1.CreateDefaultDisplayNodes()
plane1.SetPlaneType(slicer.vtkMRMLMarkupsPlaneNode.PlaneType3Points)
plane1.AddControlPointWorld(p1)
plane1.AddControlPointWorld(p2)
plane1.AddControlPointWorld(p3)
# --- Get Plane1 normal (world) ---
plane1Normal = [0.0, 0.0, 0.0]
plane1.GetNormalWorld(plane1Normal)
vtk.vtkMath.Normalize(plane1Normal)
# --- Compute perpendicular directions to plane1Normal ---
plane1Binormal = [0.0, 0.0, 0.0]
plane1Tangent = [0.0, 0.0, 0.0]
vtk.vtkMath.Perpendiculars(plane1Normal, plane1Binormal, plane1Tangent, rotationOfPerpendiculars)
n2 = plane1Binormal if useBinormal else plane1Tangent
vtk.vtkMath.Normalize(n2)
# --- Create Plane2 (point + normal) ---
plane2 = slicer.mrmlScene.AddNewNodeByClass("vtkMRMLMarkupsPlaneNode", plane2Name)
plane2.CreateDefaultDisplayNodes()
plane2.AddControlPointWorld(plane2Coordinates)
plane2.SetNormalWorld(n2)
print("Plane1 points:", p1, p2, p3)
print("Plane1 normal:", plane1Normal)
print("Plane2 origin:", plane2Coordinates)
print("Plane2 normal:", n2)
return plane1, plane2
f = slicer.util.getNode("F_1") # replace "F" with your fiducials node name
plane1, plane2 = createPlanes(
f,
plane2Center=[-96.348, 89.051, -9.788],
angle=0.0,
useBinormal=False
)
#useBinormal = True create another perpendicular plane
This is for another work so the naming and some parts were a bit confusing. You could pretty much ignore lines 1-23.
You need to first create a fiducial markup F_1 or your preferred name (you need to change line 82 getNode("F_1")) with three points to define a plane. You can place the three points along your mid-sagittal plane. It will create a plane called Plane
Then you need to define plane2Center=[-96.348, 89.051, -9.788]at line 85. You can probably switch the numbers to the coordinates of your sagittal plane’s center.
It will create a perpendicular plane named as Plane_7mm according to the normal of plane1.GetNormalWorld(plane1Normal).
Hopefully it works for your case.
