The shoulders we stand on.

Gravitation would not exist without the elegant formulation of Schwarzschild spacetime created by Thomas Müller and Jörg Frauendiener described in their paper, Interactive visualization of a thin disc around a Schwarzschild black hole.

Additionally, Gravitation was inspired by the work of Kavan G in his video, Simulating Black Holes in C++. And by Eric Bruneton's phenomenal real-time WebGL renderer and paper Real-time High-Quality Rendering of Non-Rotating Black Holes.