Field viewer

The Field Viewer tab shows what a run wrote inside the domain: surface current on a conductor layer in 2D, and the 3D E, H, and energy volumes. Two mode buttons at the top of the toolbar switch between them.

Both views share one toolbar. A slider with prev and next buttons scrubs frames, the colormap and geometry-overlay controls sit on the second row, and the corner freshness badge reads Latest results when the view matches the current project or a stale warning once you edit after the run.

Surface currents

Surface Currents is the default mode. It draws the current-density magnitude |J| on one conductor layer as a heatmap, with a colorbar in A/m and the layer name in the status bar. The conductor outline is overlaid as a white contour.

Frequency and Time switch the domain. Frequency shows the steady-state current at each DFT point, labelled in GHz, and is the default. Time steps through the recorded time-domain frames, labelled in picoseconds, and Play auto-advances them. Play is hidden in the frequency domain, which is a static sweep. Each domain keeps its own scrub position.

Range sets how the colour scale is chosen: Local rescales to the current frame, Global spans every frame in the domain, and Ref-based pins the scale to one reference frequency or frame that you pick. Cmap selects the colormap. Drag to pan, scroll to zoom.

To record surface currents, turn on enable_surface_currents and name the conductor layer in surface_current_layer. The run refuses if that layer is not a conductor. Time-domain frames are written every surface_current_interval steps, or at an automatic stride of about ten samples per period at f_max when the auto interval is on. The frequency-domain DFT accumulates every step regardless of the frame interval, over surface_current_num_freqs points (default 63).

E/H fields

E/H Fields renders the 3D field as a volume: a translucent glow over the whole domain with a lit hot core where the field is strongest, drawn over the geometry mesh. It is a time-domain view that plays through the exported frames.

Three quantities can be exported and viewed, each written as one frame per step:

export_e_mag is the default content. H is time-centered to the E level before the magnitude, and energy density combines the aligned E and H at each cell. The Source selector appears when a run wrote more than one of them, and picks which the volume shows. A run that wrote E alone keeps the plain toolbar.

Range sets the colour scale: Local for the current frame, Global across all frames, or Frame-based pinned to a reference frame you pick. Global scans every frame off the main thread, so the view holds the local scale until it finishes. Cmap selects the colormap, Geometry toggles the structure overlay, and the opacity slider sets its transparency.

Export cost and cleanup

Field export is heavy. A VTK run writes one volume per exported quantity per frame, so files reach hundreds of MB or more with a matching disk and runtime cost. Two settings bound the volume of data:

• The capture interval, dense for smooth playback or sparse to save disk.
• The step-range window (field_export_range_enabled with a start and end step), which drops warm-up frames. The solver still runs every step, only the disk write outside the window is skipped.

FDTD tips covers when the fields are worth exporting. The on-disk frame formats are on File formats and outputs.

export_vdb writes OpenVDB volumes instead of VTK, in the format on that same page. VDB carries |E| only, so the Source selector is E-only for a VDB run.