This is an aurora landscape visual that I created with HLSL. The lake and forest background assets were created by Re-Logic.

This effect is multifaceted, with a variety of moving parts, including the aurora itself, the star backdrop, and the reflection effect on the lake below. Importantly, the background elements (aka the aurora and stars) are all drawn separately to a background render target. This acts as a canvas that can be used both for rendering the actual background itself, as well as something that can be sampled when performing reflections over the lake texture, adhering the idea that reflections are more noticeable the less close they are to the observer.

The aurora itself is colored via a gradient mapping, making it so that brighter values in the shader's results are mapped onto a palette (in this case teal, turquoise, and lime hues). In terms of the strands and colors, much of it was, candidly, messing around. Experimenting with raymarching, to be specific. But there was some planning that went into the concept. The central idea behind the aurora is that of a plane oriented in 3D space in the sky that serves as the area in which the aurora "rests" upon and is oriented by. Shapes and "strands" in the aurora are composed largely of warping noise, similar to the background of this website, albeit with far greater detail, and with the help of some sinusoidal functions that operate based on the Z position of the aurora's sample, to make it more wavy.

As for the stars, they were actually kind of easy. Just some good old GPU instancing on a precomputed buffer of quadrilaterals that compose the many stars in the sky. Twinkle pulsation effects are achieved via a shader that operates on the instances during rendering.