storm_cloud

A horizontal sheet of storm cloud. The sheet is a large flat plane; this shader turns it into weather. Fractal noise over world XZ, drifting with the wind, is thresholded into cloud and clear; the sheet fades out radially so its edge is never a straight line, fades out again as it approaches the camera's own altitude so a sheet the viewer is passing through never draws as a hard slice across the frame, and shades from a dark underside to a lit top with a warm rim where the low sun is behind it. Stack several at different heights and the result is a deck: overcast ceiling from below, whiteout inside, a floor of cloud from above.