Fix vtkCutter and add test for ContourLoopExtraction - #3637
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finetjul
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Sep 7, 2026
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| // Remove duplicate points |
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you only remove duplicate cells, not duplicate points, do you ? (when you remove a cell, you are not removing its associated points)
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intersectedEdgesList lists intersected edges of the current cell, with associated intersection point. So I'm removing a point of this list so that it's treated as a line and not as a poly with a duplicated point.
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Does it mean the VTK C++ implementation also has the problem ? If so, please report a bug in VTK |
Fix bug in vtkCutter where the output would be invalid if the cutting plane intersecting a point of the input mesh
Change initial values and bounds of example's parameters to allow exploring the mesh properly
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I didn't look into the C++ implementation but it does not produce this invalid result, I used a local python vtk as a truth test. |
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Context
vtkCutter yields invalid results if the plane intersects a point of the cut mesh. This is visible on vtkContourLoopExtraction's example where the loop extraction returns 8 loops (visibly 3: pink, green, pink but each actually has multiple layers under).
Results
By properly handling cases where the plane intersects a point, we can fix the issue and have only 2 loops (red and green):
Changes
Properly differentiate the 3 cases: negative sign, null sign (on plane) and positive sign
Dedupe points, result of a same point being counted twice.
For the green triangle, intersected in one of its vertices by the red plane, 2 edges will be counted as intersected on the same position.
Added a non-regression test on ContourLoopExtraction
Modified ContourLoopExtraction example's parameters to fit with the model's bounds.
PR Checklist