Atomic Systems

In the snowy, and rainy modes in MSTS, the sky is textured in a gloomy white sort of colour. Does anybody know what the name of this file is please?

Is the same file associated with both rain and snow?

The sky layer details can be found in the route EnvFiles folder.
For EUROPE1 and 2 they are UKsun.env - UKrain.env and UKsnow.env
For JAPAN1 they are J1sun.env - J1rain.env and J1snow.env and for JAPAN2 J2sun.env - J2rain.env and J2snow.env
For USA1 they are USA1sun.env - USA1rain.env and USA1snow.env and for USA2 USA2sun.env - USA2rain.env and USA2snow.env
The basic structure of the rain / snow sky has three layers.
The top layers are starsky.ace with rainsky.ace or snowsky.ace
The bottom layer is either rainskylo.ace or snowskylo.ace
The ace files are kept in the route`s EnvFile`s Textures folder.
I suggest that you use have a look at the textures using TGATools, and see which one you need.
Cheers
Reg

Thanks for the information about the structuring. It opens an interesting can of worms.

I have been able to get a look at the upper part of the sky, by placing a track piece very high above the ground, and angling the camera sufficiently enough. My modified ace file does appear up the top, yet this mysterious whiteness in this screenshot below still appears coming immediately off the horizon.


It does not appear to be in the route's envfiles textures folder. Is it located somewhere else? Or have Kuju cropped a small portion of one of their textures to render the colour? It has me baffled.

Skies can be quite complicated, but fun to play about with, but remember to keep a copy of the original before you attempt any changes.
The default rain and snow environment skies have the top layer for daytime running as rainsky.ace and snowsky.ace, both are opaque. Confusingly, you will find rainsky.ace in the snow .env file and snowsky.ace in the rain.env file.
Below the top layers is rainskylo.ace and snowskylo.ace. these layers carry the images of the dense clouds, and are semi-transparent which allows some of the upper layer to show through, with glimpses of the sun and moon.
The sky layers do not reach down to the ground, and this can give a visible lower edge, I think the sim relies on the rain or snow affects to obscure this effect.
If you would like to get rid of this edge then you will need to modify the .env file like this.
Look for these lines

world_sky_layer_edge
(
world_sky_later_edge_steps
(
1
world_sky_layer_edge_steps_height ( 300 ) <------------- alter this figure to zero or even a negative value
world_sky_layer_edge_steps_radius ( 1950 )
)
)

This will apply to both the first and second layers
Hope this helps