Dynamic Sky & Reality Sky

Dynamic Sky & Reality Sky are a series of two demos by Spooky Iluha which showcase some interesting environments and a day/night cycle. Dynamic Sky was released on 7 Feb 2025 and Reality Sky was released on 02 August of the same year.

You can get the demos from their download page by using the password reachtheskybox. You can also find the source code for Dynamic Sky on Github, Reality Sky is TBD.

About Dynamic Sky & Reality Sky

Both demos follow the same format of being an environment that you can look at and explore. Let’s have a look at each on in order of release.

Dynamic Sky

This is a demo which displays a 3D city that you can explore. There are tall buildings and short buildings throughout, and you can travel between them and through them.

The main purpose of the demo is to demonstrate the idea of a sky dome – pretty much just a sky box (3D object to represent the background) but round rather than a six-sided cube. It gives it a more natural feel at the expense of having to draw more polygons. It’s not quite practical, given that there are 2,178 vertices and 736 triangles which would take up a significant amount of time to process.

I couldn’t get it working on a real N64 since it crashed withing a few seconds of booting, so I only got it to work on an emulator.

Reality Sky

With the N64, the sky is the limit. And so once again I was thinking on how to render it better and made an improved RealitySky™.

I’ve combined a physically-based way of calculating the volumetric Rayleigh/Mie scattering with real-time lit rendering for the volumetric clouds. And I made it performant enough to just cost 500-2000 usec per frame on CPU depending on the movement.

You can play with the demo attached, D-Pad to move the camera, C-Buttons to move the sun, hold L/R to change sun’s speed, there’s still some stuff to improve.

Spooky Iluha

I think that puts it best. It’s trying to simulate the effects of atmospheric particles on how they disperse and diffuse light.

Unlike the other demo, you can only rotate your camera, not translate it. Not that there’s much to discover given that it’s an infinite plain of sea.

Review and Conclusion

Both Dynamic Sky and Reality Sky demonstrate that you can have complex sky graphics on the Nintendo 64. Most games at the time had static skies with scattered clouds that were meant to look plausible without being distracting.

These demos flip the script by giving us a true environment in which to wrap ourselves in, a sunset to grow drowsy in and a sunrise to admire wistfully.