Gravitational Lensing by Spinning Black Holes in Astrophysics, and in the Movie Interstellar

TL;DR

This paper introduces DNGR, a rendering code that simulates realistic visualizations of spinning black holes for movies, providing new insights into gravitational lensing near black holes and demonstrating its use in the film Interstellar.

Contribution

The paper presents DNGR, a novel rendering technique for accurately depicting black holes in motion, and offers new insights into gravitational lensing effects near spinning black holes.

Findings

DNGR produces IMAX-quality images of black holes.

New equations for light propagation near Kerr black holes.

Application of DNGR to generate Interstellar's black hole visuals.

Abstract

Interstellar is the first Hollywood movie to attempt depicting a black hole as it would actually be seen by somebody nearby. For this we developed a code called DNGR (Double Negative Gravitational Renderer) to solve the equations for ray-bundle (light-beam) propagation through the curved spacetime of a spinning (Kerr) black hole, and to render IMAX-quality, rapidly changing images. Our ray-bundle techniques were crucial for achieving IMAX-quality smoothness without flickering. This paper has four purposes: (i) To describe DNGR for physicists and CGI practitioners . (ii) To present the equations we use, when the camera is in arbitrary motion at an arbitrary location near a Kerr black hole, for mapping light sources to camera images via elliptical ray bundles. (iii) To describe new insights, from DNGR, into gravitational lensing when the camera is near the spinning black hole, rather than far away as in almost all prior studies. (iv) To describe how the images of the black hole Gargantua and its accretion disk, in the movie \emph{Interstellar}, were generated with DNGR. There are no new astrophysical insights in this accretion-disk section of the paper, but disk novices may find it pedagogically interesting, and movie buffs may find its discussions of Interstellar interesting.