# 2D dielectric cylinder forward-T vs Tidy3D

<span class="validation-badge">validated · 2026-08-28</span>

<div class="case-meta"><span>forward</span><span>resolution 1</span><span>parity</span><span>p1</span><span>mie</span><span>scattering</span><span>tidy3d_golden</span></div>

This case compares a local FDTDX result with pinned reference data generated by Tidy3D.

```{figure} ../../_static/generated/dipole_field.png
:alt: Technical schematic associated with 2D dielectric cylinder forward-T vs Tidy3D

Representative radiating-field structure.
```

## What is exercised

Forward flux ratio with/without eps=2.25 cylinder (r=0.25µm). Loose tol for staircasing.

This case runs at its declared full benchmark resolution (resolution factor 1.0).



## Recorded result

| Metric | Observed / error | Reference / limit | Error | Effective budget | Result |
|---|---:|---:|---:|---:|---:|
| `T_through` | 0.798438 | 0.892698 | 0.0942596 | 0.187124 | <span class="metric-pass">PASS</span> |

The table is rendered from `progress.json`; it is not a hand-written success claim. For metrics that report an error directly, the “observed” column repeats that error and the reference column is the acceptance threshold.

## Reproduce

```bash
uv run fdtdx-bench run --case parity_mie2d_cylinder
```

Implementation and provenance: `benchmarks/cases/parity_mie2d_cylinder/case.yaml`, `benchmarks/cases/parity_mie2d_cylinder/run.py`, `benchmarks/goldens/parity_mie2d_cylinder.npz`.

[Return to the example atlas](../index.md)