A lot of research went into the SilverLining Sky, 3D Cloud, and Weather SDK, and today it’s powering realistic skies in virtual reality simulators across the world. This is high-tech stuff!
But, a lot of old-school scientific work went into SilverLining. SilverLining’s sky is basically a physical simulation of how light scatters through the atmosphere, and those physics were around long before we were.
One problem we ran into was simulating twilight conditions. There was existing research on creating real-time daytime skies where the sun is above the horizon, and for nighttime scenes past twilight. But nobody had a good model for quickly simulating twilight skies that we could find.
We found the answer in an unlikely place: the 1961 nautical atlas pictured above.
This book is long out of print – we bought it through a specialty bookseller online. It’s one of those books that makes you sneeze when you open it up – it just reeks of “old book smell,” something you don’t often get in this age of e-readers and tablets. Buried inside we found this graph:
This gives us experimental data on how much sunlight there is at a given sun altitude. We use this curve to interpolate between our daytime and nighttime sky models in a realistic manner.
It’s just a good reminder that some research really stands the test of time, and few people are out there even trying to replicate much of it today. The theory of Rayleigh scattering that so much of SilverLining is based upon dates back to the 1800’s. We also use a model of cloud size distribution that dates back to experimental data from the 1940’s taken from some guy who flew over Florida as storms started to form in the afternoon and meticulously measured the size and position of every cloud in scores of photographs. Even our atmospheric scattering model is derived from typewritten research from the now-defunct Solar Energy Research Institute in 1984, and it holds up to anything today.
The Triton Ocean SDK also has a few old-school roots in it. One of our references is the 3-volume Shore Protection Manual from the US Army from the early 80’s, and it is absolutely filled with useful equations for real-time simulations of oceans:
This bad boy is marked up, beat up, and held together with scotch tape. Inside, the pages are typewritten and the graphs created by hand. It’s fun to imagine how it was used before it fell into our hands.
It’s always best to search for the most recent research on a topic, but sometimes going back in time a bit yields information that’s even more thorough and practical to apply. We like to think that our modern era has the highest scientific standards, but in reality, there was some amazing work a few decades ago that’s as complete as anything you’d see today – perhaps even more so. The fact that such a complete understanding of natural phenomena existed without the benefits of ubiquitous computers and satellite data makes it all the more impressive.