I’ve been working on a lot of various things recently, which I will post-up soon. For the time being, here are some screenshots outlining the workflow (thus far) for a procedural sky system. I stress the word ‘procedural’ because no photographs have been used anywhere in the process.The idea here is to develop a highly robust and dynamic sky shader that will be aesthetically sensitive to the time of day. That is to say, as the sun/moon travels across the sky, the clouds, atmosphere and so forth will be lit accordingly. For this reason, I decided that using Maya’s fluid simulation system would be a good option for cloud generation, as I could create special texture maps that wouldn’t be possible using traditional photography techniques. Two such maps are included below; the first is an up/down map in which white signifies upwardness, and the second is simply an opacity map. I have also created diffuse and normal maps but these are for experimental purposes and may not be used.
There are three primary layers that are to be taken into account by the shader. In order of stacking, they are: the star layer, the atmosphere layer and the cloud layer. I haven’t decided yet if the time of day will be driven by the light vector direction or by an arbitrary counter, but ultimately it will manifest as a value modulating between 0.0 and 1.0. This value will then be broken down into quadrants and used to interpolate between lighting conditions for sunrise, midday, sunset and midnight.
I have included a screenshot of the sky material’s UDK node network but this is by no means representative of the final thing; some of the shader currently exists only as scribbles in my notepad.