Interstellar rendering references

The Kerr-Schild Hamiltonian ray integrator is an independent implementation
of general-relativistic equations. NPGS BlackHole_common.glsl was inspected
as a reference for adaptive ray integration and staged rendering; no NPGS
source code is included in this distribution. NPGS is licensed under GPL-3.0.
Reference: https://github.com/baopinshui/NPGS/blob/master/NPGS/Sources/Engine/Shaders/BlackHole_common.glsl

The Page-Thorne thin-disk flux expression in physics.js was adapted from
grtrans kerr.f90/krolikc and fluid_model_thindisk.f90.
Reference: https://github.com/jadexter/grtrans
Please cite: Dexter (2016), arXiv:1602.03184; Dexter & Agol (2009), arXiv:0903.0620.
This site does not include the grtrans Fortran runtime, geokerr elliptic
integrator, full polarized transfer solver, or GRMHD simulation data.

Further reading for the visual model (inspected for method; no source code
included in this distribution):
- Mummery, Ingram, Davis & Fabian (2024), arXiv:2405.09175 - finite ISCO
  stress, plunging four-velocities, invariant frequency shifts, and the
  radiation-pressure temperature law (equations 3, 47 and 59).
  https://arxiv.org/abs/2405.09175
  The live-particle model uses delta_J=0.02 and an injected proper radial
  speed of 0.01c. Its E is solved from the timelike radial potential at
  ISCO with circular-orbit L retained. This finite-inflow regularization
  is not the paper's complete atmosphere or GRMHD model.
- James, von Tunzelmann, Franklin & Thorne (2015), Class. Quantum Grav. 32
  065001, arXiv:1502.03808 - DNGR ray-bundle rendering of spinning black holes.
- Gralla, Holz & Wald (2019), Phys. Rev. D 100, 024018, arXiv:1906.00873 -
  shadow, lensing ring and photon ring image decomposition.
- Bruneton (2020), arXiv:2010.08735 - real-time shader via precomputed
  deflection tables; alternative performance route.
- Luminet (1979), Astronomy & Astrophysics 75, 228 - first computed image of
  a spherical black hole with a thin accretion disk.
- Event Horizon Telescope Collaboration (2019), ApJL 875 L6 (Paper VI) -
  observed ring asymmetry from relativistic Doppler beaming.
- oseiskar/black-hole (GPL) and rantonels/starless (MIT) - background lensing
  and multiple star-image presentation references; physics write-up at
  https://oseiskar.github.io/black-hole/docs/physics.html

Current volume / polarised renderer (2026-10-05):
- Gammie, McKinney & Toth (2003), HARM, arXiv:astro-ph/0301509.
- Numerical GRMHD movie generated locally by running AFD-Illinois/iharm2d_v3,
  pinned commit bfa06d2cbabf2c8cd94c1711d04fd468397e9aee. Only numerical
  fluid records and provenance are distributed; upstream C source/executables
  are not included. Parameters, checksum and measured errors are in
  data/grmhd-torus.json; the reproducible recipe is tools/generate-grmhd.py.
- The browser continuation ABI is an independent Rust implementation in
  tools/grmhd-runtime.rs, compiled from the same source for native and
  wasm32. It restores the published GRMHDCP1 float64 checkpoint and provides
  the conservative scalar finite-volume continuation described in PHYSICS.md;
  it is not a redistribution of iharm2d_v3 and is not claimed to be a
  complete upstream GRMHD restart. Build commands, compiler version and hashes
  are recorded in solver/grmhd-runtime.json.
- Dexter (2016), equations 93-101, 136 and 145-147: thermal synchrotron,
  absorption and Faraday coefficients. Independently implemented formulae,
  not the complete grtrans solver or atmosphere.
- Wyman, Sloan & Shirley (2013), Simple Analytic Approximations to the CIE XYZ
  Color Matching Functions, JCGT 2(2), 1-11.
  https://jcgt.org/published/0002/02/01/
- Bronzwaer et al. (2018), RAPTOR I, arXiv:1801.10452: time-dependent
  radiative transfer reference. No RAPTOR source is included.

The renderer has finite resolution/history and approximate atmosphere and
thermal-emission coefficients. Its illustrative masses/accretion rates,
electron heating prescriptions and display gains are not observational fits.

A full per-effect derivation trail lives in PHYSICS.md at the repository root.

The applicable grtrans MIT notice follows:

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