3D Plotting"
In orbitr: A Tidy Physics Engine for Building and Visualizing Orbital Simulations

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  fig.width = 7,
  fig.height = 5
)

library(orbitr)

All simulations in orbitr run in full 3D — every body always has x, y, and z coordinates. When all motion happens in the XY plane (i.e., z = 0 and vz = 0 for every body), plot_orbits() produces a static 2D ggplot2 chart. The moment any body has non-zero Z motion, plot_orbits() automatically switches to an interactive 3D plotly visualization — no code changes needed.

You can also force 3D rendering for planar data with three_d = TRUE, which can be useful if you want the interactive rotation and zoom capabilities even for a flat system.

How the 2D/3D Dispatch Works

plot_orbits() checks whether any(sim_data$z != 0). If there's any Z-axis movement — or if you pass three_d = TRUE — it hands off to plot_orbits_3d(), which uses plotly for interactive 3D rendering. Otherwise it falls back to a static ggplot2 chart.

If plotly isn't installed, the function warns you and falls back to the 2D plot even for 3D data.

A Tilted Lunar Orbit

The Moon's real orbit is inclined about 5° to the ecliptic. You can approximate this by giving the Moon a small vz component:

create_system() |>
  add_body("Earth", mass = mass_earth) |>
  add_body("Moon",  mass = mass_moon,
           x = distance_earth_moon,
           vy = speed_moon * cos(5 * pi / 180),
           vz = speed_moon * sin(5 * pi / 180)) |>
  simulate_system(time_step = seconds_per_hour, duration = seconds_per_day * 28) |>
  plot_orbits()

Because vz is non-zero, plot_orbits() detects 3D motion and returns an interactive plotly widget. You can drag to rotate, scroll to zoom, and hover to see timestamps.

Forcing 3D for Flat Data

Even if your system is entirely planar, you can opt into the interactive 3D viewer:

create_system() |>
  add_body("Earth", mass = mass_earth) |>
  add_body("Moon",  mass = mass_moon, x = distance_earth_moon, vy = speed_moon) |>
  simulate_system(time_step = seconds_per_hour, duration = seconds_per_day * 28) |>
  plot_orbits(three_d = TRUE)