The Plot Engine is a flexible plotting workbench. In 2D mode you overlay as many curves as you like, each with its own settings — for example T at 0° s-pol beside T at 45° p-pol beside R for the total system — on one chart. In 3D mode you map a single quantity over two swept variables as a rotatable surface or a heatmap, including the merit-function landscape your design sits in. The sidebar toggle switches modes, and each design’s plots are remembered as you move between windows.

Settings

2D curves

Add a curve and configure it:

X axis — wavelength (nm) or AOI (°), with a from/to range and step.

Y — the channel to plot: T, R or A.

Polarization — s, p or averaged.

Surface — front, back or total.

AOI fixed / λ fixed — the value held constant for whichever of AOI or wavelength is not the x-axis.

Dash / width / color — line appearance, and a visibility checkbox per curve.

3D surface

Quantity (Z) — what to map: T, R, A, or the Merit Function. For an optical quantity you also pick a polarization and surface mode. The merit function is exactly the quantity the optimizer minimizes, so the surface shows the basin your design occupies.

X axis / Y axis — each axis is built in two steps: choose the target (wavelength, AOI, or a specific layer, listed one per layer), then, for a layer, the property to vary (thickness, n or k). Set a from/to range and a step count. Sweeping a layer’s n or k temporarily substitutes a constant-index material for that layer. Merit-function axes must be layer parameters — wavelength and AOI are integrated out of the merit function and are rejected.

Fixed λ / AOI — shown only for whichever of wavelength or AOI is not on an axis.

Render — a 3D surface or a flat heatmap.

Colors — the colorscale (Viridis, Cividis, Jet, and others).

Compute surface — runs the grid. The point count is shown beneath the button, and a counter reports progress; large grids stay responsive while they compute. Per-axis steps and the total grid size are capped to keep runs manageable.

How to read it

In 2D, every visible curve is drawn on a shared T / R / A axis (fraction), so overlaying curves with different angles, polarizations or surface modes lets you compare them directly. Use it for angle-of-incidence sweeps (one curve per angle) or polarization comparisons.

In 3D, a T/R over wavelength × AOI surface is an angle-robustness map, while a merit function over two layer thicknesses is the optimization landscape — handy for confirming a refined design sits in a genuine basin or for spotting a better one nearby. You can export any plot as PNG or SVG from the chart’s built-in toolbar.

References

• H. A. Macleod, Thin-Film Optical Filters, 5th ed., Ch. 2.