Clouds from Space

Noisy Clouds

Terragen 2 (and many other applications) use algorithmic noise to create realistic clouds. Invented by Ken Perlin, Perlin Noise is a fast-to-compute and realistic function for simulating many natural features including clouds and terrain. Ken posted a great introduction at http://www.noisemachine.com/talk1/.

I’m just beginning to explore clouds and am sure there’s room for improvement. Advice/suggestions are appreciated.

The Right Noise

There are several parameters that control the shape and scale of Perlin Noise. I started with a few forum posts at Planetside:

http://forums.planetside.co.uk/index.php?topic=144.0

http://forums.planetside.co.uk/index.php?topic=540.0

but the clouds weren’t coming out the way I want. For your reference, I’m posting the various images I created by trial-and-error along with the appropriate settings.

Here’s the settings for my cloud layer (note: for more realism, you may want additional layers)

The Images

Each of these images tweaks the settings for the pattern of clouds (shown when you click the Pattern… button).

Scale

Density

Tweak Noise

Warping

Feature Scale: 1e+006

Lead-in Scale: 1e+007

Smallest Scale: 5000

Contrast: 1

Coverage Adj.: 0.15

Roughness: 1.5

Noise Flavor: Perlin

Noise variation: 1

Var. method: Clamped multi

Buoyancy: 0.5

Clumping: 0.25

Noise Stretch: 1 1 1

Lead-in: 1 octave Perlin

Lead-in amt: 1.025

Less warp: false

Allow vert. warp: true

 

Scale

Density

Tweak Noise

Warping

Feature Scale: 5e+005

Lead-in Scale: 1e+007

Smallest Scale: 5000

Contrast: 1

Coverage Adj.: 0.15

Roughness: 1.5

Noise Flavor: Perlin

Noise variation: 1

Var. method: Clamped multi

Buoyancy: 0.5

Clumping: 0.25

Noise Stretch: 1 1 1

Lead-in: 1 octave Perlin

Lead-in amt: 1.025

Less warp: false

Allow vert. warp: true

 

Scale

Density

Tweak Noise

Warping

Feature Scale: 5e+005

Lead-in Scale: 5e+006

Smallest Scale: 5000

Contrast: 1

Coverage Adj.: 0.15

Roughness: 1.5

Noise Flavor: Perlin

Noise variation: 1

Var. method: Clamped multi

Buoyancy: 0.5

Clumping: 0.25

Noise Stretch: 1 1 1

Lead-in: 1 octave Perlin

Lead-in amt: 1.025

Less warp: false

Allow vert. warp: true

 

Scale

Density

Tweak Noise

Warping

Feature Scale: 2e+005

Lead-in Scale: 4e+006

Smallest Scale: 5000

Contrast: 1

Coverage Adj.: 0.15

Roughness: 1.5

Noise Flavor: Perlin

Noise variation: 1

Var. method: Clamped multi

Buoyancy: 0.5

Clumping: 0.25

Noise Stretch: 1 1 1

Lead-in: 1 octave Perlin

Lead-in amt: 1.025

Less warp: false

Allow vert. warp: true

 

Scale

Density

Tweak Noise

Warping

Feature Scale: 1e+005

Lead-in Scale: 3e+006

Smallest Scale: 5000

Contrast: 1

Coverage Adj.: 0.15

Roughness: 1.5

Noise Flavor: Perlin

Noise variation: 1

Var. method: Clamped multi

Buoyancy: 0.5

Clumping: 0.25

Noise Stretch: 1 1 1

Lead-in: 1 octave Perlin

Lead-in amt: 1.025

Less warp: false

Allow vert. warp: true

That’s starting to look a bit better. Let’s back out and look at the whole planet.

For comparison, here’s the Earth:

The pattern is not bad at all, but could be brighter. Let’s increase the Cloud density from 0.0002 to 0.001

Clouds appear more compact (not spread over as wide an area), and brighter. Let’s crank Cloud density up by 10x again, to 0.01

Getting quite bright, but the clouds are also getting smaller and smaller. Let’s dial down the Coverage Adjust a bit and see what happens

Scale

Density

Tweak Noise

Warping

Feature Scale: 1e+005

Lead-in Scale: 3e+006

Smallest Scale: 5000

Contrast: 1

Coverage Adj.: 0.02

Roughness: 1.5

Noise Flavor: Perlin

Noise variation: 1

Var. method: Clamped multi

Buoyancy: 0.5

Clumping: 0.25

Noise Stretch: 1 1 1

Lead-in: 1 octave Perlin

Lead-in amt: 1.025

Less warp: false

Allow vert. warp: true

 

This will do nicely for my purposes!

 

 

 

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