Feat: charts

[fjebaker]

Adds AbstractChart as a method for changing the integration domain flexibly. Also adds a chart that uses event_horizon to interpolate the shape of the inner horizon poloidally, allowing better visualisations of shadows for non spherical event horizons.

using Gradus
using Plots

m = JohannsenPsaltisMetric(1.0, 0.8831, 0.4)
u = SVector(0.0, 1000.0, π / 2, 0.0)

α, β, img = @time rendergeodesics(
    m,
    u,
    # max integration time
    2000.0,
    image_width = 1000,
    image_height = 1000,
    fov = 60.0 ,
    verbose = true,
    chart = event_horizon_chart(m, closest_approach = 1.001, resolution=200),
)