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The making of Cosmosis: Remix
by merlucin | Chapter 4: Sky and clouds
There are lots of ways of generating clouds and simulate their evolution along time. We were in need of the following:

1. Wathever we do, it must be realtime
2. We want an entire evolving sky, not a single cloud

So instead of generating a cloud, we used a pre-rendered one as a particle. The cloudy sky is then reduced to an equation for the particle system, defining the source, size, position and alpha of the clouds along time.

  
For the cloud sources position we used a simple plane, that was defining the skyline. The clouds limit was blended with a sundown skybox, by simply reducing the clouds' alpha to zero when they were far enough from the viewer.

For the clouds particle, there are lots of them to choose from. We chose one with a white base and a gradual fade to black (black means transparent, with the blending parameters we used). This texture was static along all the effect. However, changing the clouds texture results in interesting effects that could be explored in future productions.

  
Xphere, Isaac2 and I were working in this scene while watching the evoke demos through the video stream that demoscene.tv kindly provides. Then xphere said that the demos appear better in an stream that in the computer's screen.

I don't know why, but the demos or games you play with an oldschool machine like a msx or the amiga, always with a tv instead a monitor, have a really good appearance despite of the low resolution. Perhaps it is because the pixels aren't perfect squares like now in the tft monitors, and appear blurred. Isaac2 started to work in a shader designed to slightly distort the scenes with noise, simulating a video stream.

  
The final version of the shader didn't convert the appearance to the one you can appreciate in a stream but was adding dirt enough to the scene to cover the small errors you always have. We liked the result, so most of the scenes are painted with this shader. The shader uses a texture as deformation information that is applied to the scene, with a configurable offset and intensity. I think that we will use it in future prods. There is potential there :)
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