FDTDX vs Step
FDTDX
fdtdx.readthedocs.ioStep
apps.kde.orgSide by side
| Figure | FDTDX | Step |
|---|---|---|
| Price from | Free | Free |
| Free plan | Yes | Yes |
| Free trial | — | — |
| Open source | — | — |
| Linux | Yes | Yes |
| Self-hosted | Yes | — |
| Plans published | 1 | 1 |
| Spec score · Physics Simulation Software | 8.6 (#12) | 8.2 (#22) |
| Authoring tools | Yes | Yes |
| Delivery mode | desktop | desktop |
| Free plan | Yes | Yes |
| Lesson library | No | Yes |
| Purpose | FDTDX is an open-source Python package for simulating and designing three-dimensional photonic nanostructures with the Finite-Difference Time-Domain method. | Step is an interactive physical simulator for exploring the physical world through simulations. |
| Support | The FAQ invites users to open GitHub discussions for unanswered questions and issues for suspected bugs, and says the maintainers regularly check discussions. | Help is available through the Step Handbook, KDE forum, the kde-edu mailing list, and the #kde-edu Libera.chat channel. |
| 3D visuals | Yes | No |
Plans
In their own words
Step
Step is a free Linux desktop application for exploring physical systems through interactive simulations. Users can change body and force properties while a simulation runs. Supported models include two-dimensional classical mechanics, molecular dynamics, sound waves, and deformable bodies, with particles, damped springs, gravitational and Coulomb forces, rigid bodies, and collision handling. Step calculates unit conversions, expressions, error propagation, and solver error estimates. Explicit and implicit solvers reach 8th order, with optional adaptive timesteps; most require GSL. Graph, meter, and tracer tools visualize results, while a controller changes properties using keyboard shortcuts. Tutorials, example experiments, object information, and an integrated Wikipedia browser provide learning material. More examples can be downloaded through KNewStuff. Expression calculations such as unit conversion require libqalculate. Step is GPL-2.0+ software, and its StepCore library can be used separately. The listed release is Step 26.08.2, released 2026-10-08.