Has Windlight been changed?

[WolfBaginski Bearsfoot]

I have been trying various Windlight presets.

I see very fast cloud movements. This is controlled by two Cloud Scroll settings, which are in the Windlight .xml that defines the preset. The highest value I have seen in any of these files is 20 (they define a vector for the cloud motion in the X,Y plane). In the editor window they are set with sliders.

So far, so good.

The trouble is that these setting provide a very high speed motion on my computer, which isn't particularly powerful. But, with a vector manitude of about 2, I am seeing distant clouds cross my field of view in about two seconds.

I have not found any dependency on the Draw distance setting.

Even if the clouds are no more than a 32m draw distance away, the apparent wind speed is Force 10 on the Beaufort Scale, which on land is described as "Trees uprooted, considerable structural damage occurs". If the clouds are further away, the wind speed is higher.

I checked this with a couple of different viewers, though I couldn't even get the SL Linux viewer to run. It doesn't look as though they modify the Linden code on this. Firestorm has a magnitude scale of 0-300 on the sliders. On a hunch, I checked with Cool VL Viewer, which has the UI, at leat, based on the v1 code. The magnitude range is 0-10. The graphics engine follows the current Linden codebase, and the Windlight preset files are the same, giving the same rapid movement of clouds.

So what's changed?

Advanced Lighting has no effect on the movement. The clouds do depend on Atmospheric Shaders: turn thenm off and the clouds vanish.

It looks like a mix of erratic UI design (the slider operation, and different viewers allowing such widely different ranges) and a change in the graphics engine that didn't get noticed.

[Nalates Urriah]

Typical settings that work for cloud scroll in FS and SL are >-1 and <1. My sunny day leisurely clouds scroll at 0.20 and 0.01.

You may have to click on the slider, let go, and then use the arrow keys to move the slider. In the SL viewer you can tell the slider is selected as the button is highlighted. In FS you just have to know. It is the sort of thing that has me calling FS the power user’s viewer.

FS has alternative clouds. You can change them by adding in your own texture. So, another factor is the size of the texture being used for the clouds.

AFAIK, Windlight has not changed in years.

[WolfBaginski Bearsfoot]

I have asked people in-world, and they report seeing similar speed of cloud movement. They were using different operating systems to my computer, and of course had different hardware.

I have examined the .xml files that contain the presets, and it looks as though the number shown in the UI as set for cloud movement is not the number that is stored in the file. The data-type is specified as "real", and the format used is consistent with the format specified for that data-type, but I not found any of the files giving a negative value for the scrolling. It seems that the original Windlight spec expects a value between 0 and 20, with the numbers shifted to give a range from +10 to -10, and a file-value of 10 representing a zero.

Local RL weather has surface wind speeds of about 18mph, and the cloud movement is  visible. The apparent movement of the clouds in SL Windlight is rather faster than that of an airliner on approach to the local airfield, suggesting a windspeed of over 150 knots. It seems incredible to me that nobody has noticed.

 

[WolfBaginski Bearsfoot]

Taken from the file "Fluffy%20Big%20Clouds.xml" supplied as part of "Second_Life_4_0_6_315555_i686", the Linux version. 

    <key>cloud_scroll_rate</key>        <array>            <real>11.809999465942383</real>            <real>12.799999237060547</real>        </array>

"not changed" seems synonymous with zero QA or maintenance.

 

 

[Theresa Tennyson]

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WolfBaginski Bearsfoot wrote:

Taken from the file "Fluffy%20Big%20Clouds.xml" supplied as part of "Second_Life_4_0_6_315555_i686", the Linux version. 

    <key>cloud_scroll_rate</key>        <array>            <real>11.809999465942383</real>            <real>12.799999237060547</real>        </array>

"not changed" seems synonymous with zero QA or maintenance.

 

 

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These numbers are from Midday, where the clouds move barely perceptably:

10.199999809265137

10.01099967956543

"Fluffy Big Clouds" gives me the same numbers you get and the clouds move as quickly as you describe.

This would suggest that setting the vector to a magnitude of 2 over the baseline will give you clouds that move pretty freakin' fast.

SOOOO... don't set your vector magnitude to 2 if you don't wan't clouds that move pretty freakin' fast, apparently.

[Madelaine McMasters]

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WolfBaginski Bearsfoot wrote:

Force 10 on the Beaufort Scale

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I love that kind of talk. It reminds me of my kite flying days.

;-).

[SabaothMastema]

Two thoughts come to mind. One; perfect conditions for speed sailing. Two; I should see if my insurance covers these weather conditions.

[Penny Patton]

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Nalates Urriah wrote:

AFAIK, Windlight has not changed in years.

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That reminds me, LL never even finished the initial Windlight release. We're still missing a bunch of features LL said would be included.

• Windlight settings shared as inventory.
• The "Nimble" volumetric clouds to replace the old particle clouds. 
• Weather settings. 

The last change to Windlight was LL fixing the day cycle editor a few years ago (it had been broken for years since the initial release).