ParaView outputs

This project can export results to VTK XML formats so you can inspect them in ParaView (or any VTK-capable tool) without running the interactive GUI.

File formats

We use a minimal, dependency-free writer (torus_solver.paraview) that produces ASCII VTK XML files:

• .vtu: UnstructuredGrid (used for winding-surface meshes, point clouds, and polylines)

• .vtm: vtkMultiBlockDataSet (a lightweight “scene” file that references multiple .vtu blocks)

In most runs, you only need to open:

• scene.vtm

What gets exported

Exact content depends on the script, but common blocks include:

• winding_surface*.vtu

  • Quad mesh of the circular torus winding surface

  • Typical point data:

    • V: surface electric potential (electrode model)

    • s: injected current density (electrode model)

    • K: surface current density vector (A/m)

    • Ktheta, Kphi, |K|: decomposed components/magnitude

    • Phi: current potential (current-potential / REGCOIL-like model)

• electrodes*.vtu

  • Point cloud of electrode locations on the winding surface

  • Typical point data:

    • I_A: projected electrode currents (A) with net current constrained to zero

    • sign_I: sign(I_A) for quick thresholding/selection

• target_points.vtu

  • Point cloud of target surface points (e.g. a VMEC boundary)

  • Typical point data:

    • Bn_over_B: normalized normal field on the target surface

    • n_hat: unit normals

    • weight: area weights (discrete surface Jacobian)

• fieldlines*.vtu

  • Polyline cells representing traced field lines

  • Often includes line_id and s_index as point data for coloring

  • Some examples optionally superpose an external ideal toroidal field \(B_\phi\propto 1/R\) in the tracer. In that case, the exported field lines correspond to the total field used for tracing.

Recommended ParaView workflow

1. Open scene.vtm

2. For surfaces:

   • Use Color By → |K|, V, or Bn_over_B

   • Add Contour filters to visualize level sets

3. For field lines:

   • Use Tube to get publication-quality 3D lines

   • Color by line_id or by a scalar you compute in ParaView

Notes

• Outputs are intended to be lightweight, portable, and scriptable.

• The interactive GUIs use VTK for rendering; the exporters do not require vtk to be installed.