Question PlaneNode Normal

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1

I am currently creating planes based on 3 control points as follows:

planeNode = slicer.mrmlScene.AddNewNodeByClass(“vtkMRMLMarkupsPlaneNode”, “myPlaneNode")

planeNode.SetPlaneType(2) # PlaneTypeThreePoints

planeNode.AddControlPoint(p1[0], p1[1], p1[2])

planeNode.AddControlPoint(p2[0], p2[1], p2[2])

planeNode.AddControlPoint(p3[0], p3[1], p3[2])

However, sometimes the normal points correctly following right hand rule of order of points

i.e. it matches the normal that I can compute in python:

n1 = np.cross(p2 - p1, p3 - p1) # Normal direction for the plane

but other times the normal is flipped.

I see I can also set the plane by normal as a solution, but I want to understand how the normal is assigned for the 3 point based plane method (does it follow the right hand rule based on order of control points or not?).

Thank you.

2

The code is opensource so you can check out the implementation:

HIH

3

Thank you!

That answers my question, the bug must be somewhere else on my end.

Best,

Eva