Hamlet has an article about Stevie Davros’ enhanced skies. In 2011 Firestorm added a feature that allows replacement of Second Life™ clouds. Thank you for the computer code, Cinder Roxley. Back then Vincent Nacon was creating new cloud images for this feature.
So, this feature is not new nor limited to Firestorm. JuicyBomb wrote a tutorial NEW CLOUDS FOR SECOND LIFE, May 2013, for those using the Linden Viewer. The instructions are good for any viewer.
Not much has changed since then. I just checked in the Linden Viewer 5.1.0 and there is still no provision for selecting a different cloud texture. So, it is still a manual change.
In Firestorm the change is available in Preferences->Firestorm->Windlight (tab)->Cloud Texture (drop).
The creative Photo Tools in Firestorm do not provide any means for making a quick cloud change. And it seems a viewer restart is required to use a change.
Davros is a RL photographer into dramatic skies. He has made a new set of cloud textures and is playing with them on his Mac. He published a video Jan 10, 2018. It shows the effect of using the textures. Pretty Awesome. Also, long and boring.
Notice that he selects the cloud texture before logging in. The subsequent changes are Windlight™ changes showing how the texture works with various WL settings.
These textures are expected to appear in the SL Marketplace. No ETA, but real soon now.
The tutorials are about adding TGA files into a folder: C:\Program Files\FirestormOS-Releasex64\app_settings\windlight\clouds.
In Stevie’s video, you see a large number of files listed in the Preferences Cloud texture drop down. It is at about the 02: 00-time mark. Placing files in the ‘clouds’ folder adds them to this drop down.
All the above will get you dramatic clouds now. But, changes are coming.
Rider Linden is working on the EEP… Enhanced Environment Project. This is an improvement the Lindens are adding to Second Life™. It will change how we work with Windlight (WL). Plus, it adds new settings to WL.
I expect EEP to make it way easier to change the cloud textures and likely let us make the changes on the fly. We, hopefully, will be able to change the cloud texture as easily as we change other WL settings and see the immediate effect.
As you dig around you find the Linden Viewer has a single default 512×512 cloud texture. Firestorm has the same default image but adds three 1024×1024 images. Some people are using 4096×4096.
Size is not a limit. I’m not sure how large one could go. As these textures do NOT have to upload into SL assets there is no 1024 limit imposed by the server nor any other limit. But, the viewer is expecting a square image. So, I would stick with the “two’s” limit and square.
Those using large images claim they see no loss of performance. However, the system does have to hold the texture in video memory to render the sky. So, use as small a texture as will do the job. Larger textures increase the likelihood your viewer will start texture thrashing, clear, blurry, clear…