5 octaves of 3D simplex noise generated
on fly in GLSL shader are used to create a 3D static cloud volume
Then time is used as the third coordinate for animation.
Clouds are matched to your browser window.
"Flat" clouds are much faster on Nexus 10
(5 and 15 fps).
by Ricardo Cabello (Mr.doob) are made of many textured bilboards (to the left).
Similar to the fire demo.