Ouais peut être, ça me semble plus logique 
Sinon je viens de voir ça sur le même site, ça explique en détails le système météo (en fait le mec est chargé de la météo)
Real-time Dynamic weather systems
Lit-Animated cloud formations for planar and 3D cloud systems in full day/night cycles
Temperature based environments (Snow, ice, rain, wind, fog)
Precipitation accumulation (rolling fogs, varied snow, ice, rain, & mist)
Server side and client side manager class systems developed from scratch
Communicated with internal render manager, virtual body simulator, BattleRoyale systems, sky and satellite rendering systems, audio, and particle systems
3D-effect masking system
Rendering technique implemented to mask off areas in 3D on the GPU per pixel
Implemented to be nearly undetectable in millisecond frame cost (< 0.1ms)
Used to mask rain and snow surface effects from covered and non-covered areas
Used to mask particles like rain drops and snow flakes from falling indoors
Iris/Exposure Effect
This effect was an integration into our HDR exposure system in order to adjust exposure based on the visible scene
Accomplished by accumulating frame buffer luma/brightness over time and fed into our tonemapping and lighting algorithms
Weather tools
Developed weather integration and control into 3 different art tools
Developed a 2D HUD display including tabs, sliders, and radio buttons to control the weather in real-time for debug and design purposes
The Snow effects
The snow I developed comes in 3 parts: surface, systems, and particles
The surface effects were done in a separate render pass which modified the gBuffers for specular channels, albedo, and normals
The systems work was managing temperatures, communication with outside systems which read the temperatures, determining whether it was snowing, icey, or a static temperature and snow condition
The particles for the snow system was simple, where I kicked off a snow particle effect created by our artists whenever it snowed or stopped snowing
The Rain effects
The rain system and rendering was much more complex than snow and included many parts which make up the symphony of the rain system
One system watched over and calculated the difference of rain to snow ratios and blends and kicked off the appropriate effects
Another system received calculations from the rain-clouds to determine the amount and intensities of rain per 3D position on the map
Surface rendering was generally simple, but had to be streamlined for performance sake, where modifications were made to the gBuffers similar to snow but included surface normal and specular animations, patterns, puddling, and albedo adjustments for water saturation
Prototyping - The rain drops were probably the most difficult and time consuming part of the rain system. There were multiple prototypes and experiments done to find ways to acheive realistic rain while not impacting performance. A few screenspace attempts were made, but the best prototype turned out to be a CPU controlled layer-cycle of rain drop particles.
The rain drop particles themselves were simple with some animation, scaling, some transforms, alpha blending and clipping, coloring, lighting, and splash effects (refractive lighting did not appear realistic so it was removed)
The Rain-Clouds
3D upside-down screen-facing T posed quads with real-time generated normals and lighting
Animation and coloring incorporating in-game env-mapping, sky, fog, exposure and polarizing values
Calculated positioning, dimensions, rain-fall, and pathing on the CPU (server & client side)
http://ryanfavale.wix.com/portfolio#!h1z1-details/c1ljl
Regardez les autres screen il y en a des super beau, si ils nous réserves ça pour les agrandissement de map ça annonce du lourd 
