vtkCollisionDetectionFilter segfault

When running this script in Python, I get a segmentation fault (core dumped)

import itertools
from stl import mesh
import vedo
import vtk

fpath = vedo.download("https://ozeki.hu/attachments/116/Eiffel_tower_sample.STL")
your_mesh = mesh.Mesh.from_file(fpath)
verts = list(itertools.chain(*(your_mesh.vectors)))
faces = [[i*3, i*3+1, i*3+2] for i in range(len(verts)//3)]
vpoly = vedo.Mesh([verts, faces]).clean().polydata()
vpoly2 = vpoly

collide = vtk.vtkCollisionDetectionFilter()
collide.SetInputData(0, vpoly)
collide.SetInputData(1, vpoly2)
collide.SetBoxTolerance(0.1)
collide.SetCellTolerance(0.1)
collide.SetNumberOfCellsPerNode(2)
collide.SetCollisionModeToFirstContact()
collide.GenerateScalarsOn()
#collide.Update()

print(collide.GetNumberOfContacts())

If I uncomment collide.Update(), then it doesn't crash. In my opinion, a warning or exception should be thrown if Update was not called, to prevent your program from crashing.

This has also been mentioned in https://discourse.slicer.org/t/collision-detection-capabilities-in-3d-slicer/14854/13

changed the description

The change that is needed is in here: https://gitlab.kitware.com/vtk/vtk/-/blob/master/Filters/Modeling/vtkCollisionDetectionFilter.h#L236

if (!this->GetOutput(0) || !this->GetOutput(0)->GetFieldData() || !this->GetOutput(0)->GetFieldData()->GetArray("ContactCells"))
throw std::runtime_exception("...");
else
return this->GetOutput(0)->GetFieldData()->GetArray("ContactCells")->GetNumberOfTuples();

This security check could be better enabled in the function GetContactCells and then the GetNumberOfContacts function would just call return GetContactCells(0)->GetNumberOfTuples();

This looks like an easy fix, could you take care of it ?

Yes, I could do it. What is the recommended way for the error output?. I see that sometimes VTK issues a "[WARN]: ..." on stderr, but I am not sure of which function or format I should follow.

vtkWarningMacro

mentioned in commit ferdymercury/vtk@73b7aa6f

mentioned in merge request !8374 (merged)

mentioned in commit ferdymercury/vtk@1acddc24

mentioned in commit ferdymercury/vtk@fdca17a1

mentioned in commit ferdymercury/vtk@8b4ee221

mentioned in commit ferdymercury/vtk@ccbe9e1c

mentioned in commit 28acecb7

closed with commit ccbe9e1c

closed with merge request !8374 (merged)