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Using FastSky

Quick Start

  • Step 1 : Create a new material using the shader, Norex/FastSky.
  • Step 2 : Enable desired features like clouds, moon, and stars by checking their respective boxes.
  • Step 3 : Configure your skybox settings (refer to the section below for details).
  • Done!

FastSky Material

The FastSky material editor has two sections: Sky and Clouds. Use the navigation button below the settings to switch between them.

Sky

This section consists of the below sub-sections

- Atmosphere

atmosphere settings

PropertyDescription
Sky TintThis setting controls the atmospheric scattering. For Earth-like atmospheres, use a grayscale tint, as it influences the atmospheric scattering wavelength. For alternative atmospheres, use custom colors.
Ground ColorThe color of the ground.
Night TintThe color of the sky at night
Atmosphere ThicknessThis property enhances the Rayleigh scattering constant. Increase its value to achieve a more reddish sunset and sunrise.

- Sun

sun settings

PropertyDescription
EnabledToggles the sun's visibility.
BrightnessControls the sun's intensity.
SizeAdjusts the sun's visual size.
ConvergenceConcentrates the sun's intensity towards its direction.

- Moon

moon settings

Currently, the moon is always positioned opposite the sun, meaning it won't appear during the daytime.

While the moon's direction should ideally depend on both the sun's direction and the moon's Lunar Phase, we've found this effect usually necessary for most applications. We might make this customizable in future versions.

PropertyDescription
EnabledToggles the visibility of the moon.
ContrastEnhances the moon's surface: dark areas become darker, and light areas become lighter.
BrightnessAdjusts the moon's brightness
Lunar PhaseControls the illuminated portion of the moon. 0.0->New Moon (invisible), 0.5->Full Moon. Note: Physically, this property should affect the moon's direction, but this might not be relevant for most use cases.
Moon TextureThe texture applied to the moon's surface.
TilingControls the tiling of the moon texture.
OffsetAdjusts the moon texture's offset, creating a rotation illusion depending on the Spherification setting.
SpherificationApplies spherical projection to the moon's texture coordinates.

- Stars

star settings

PropertyDescription
EnabledToggles the star field's visibility.
SpacingControls the density of the star field
SizeAdjusts the size of the star field.
BrightnessControls the brightness of the star field.
Twinkle SpeedDetermines how fast stars twinkle.
Twinkle IntensityControls the strength of the twinkling effect.

- Exposure

exposure

Finally, there's a value that controls the overall exposure of the skybox. Below this, is the navigation button which leads you to the next section (Clouds)

NOTE

The Exposure property affects both the intensity of the sky and the clouds.

Clouds

- Global Settings

clouds global settings

These are settings perculiar the all cloud layers.

PropertyDescription
EnabledToggle's the visibility of all cloud layers.
ScatteringThe cloud scattering coefficient, resulting in the effect of the clouds being illuminated by the sun. Increasing this value concentrates the intensity of the clouds lit near the sun.
Sun Light AffectionControls how much the clouds are affected by the sun's color and intensity.

- Cloud Layers

cloud layers

You can utilize up to four cloud layers in the atmosphere. For optimal results, two cloud layers are often sufficient.

Cloud layers are stacked, with Layer 4 at the top, followed by Layer 3, Layer 2, and Layer 1.

It's often common for lighter cloud layers to be above darker ones. You can quickly achieve this by clicking the button next to the cloud layers dropdown and selecting "Stack By Luminance." This automatically arranges lighter clouds at the top and darker clouds below.

stacking by luminance


Settings

cloud layer settingscloud layer settings cont'd

PropertyDescription
EnabledToggles this cloud layer's visibility.
SHAPE-
Noise TypeCloud density sampling function. Using worley noise tends to give you a more cloud-like shapes.
Below is a list of noise functions and their computational cost value.

1. Worley - Expensive(5)
2. Worley Fast - Cheap(1)
3. Worley 2 - Expensive(5)
4. Simplex - Cheap (2)

Using fast Worley might result in discontinuities at times, but these are often unnoticeable. Therefore, it's not strictly necessary to use the slower Worley function unless you're targeting high-end devices or require extreme accuracy. The Worley 2 noise function generates more interesting cloud shapes, but it lacks a fast alternative. It also requires you to use a much more smaller Density Offset
2DUses 2D noise functions instead. While significantly faster than their 3D counterparts, 2D noise functions have the below limitations.

1. Using a Curvature > 0.6 can cause peculiar stretching along the Y-axis.

2. Clouds may appear static as they move with the wind. A workaround is to enable the Detail feature of the cloud layer, which uses an additional noise field to erode cloud edges, adding dynamism. This however still doesn't reproduce the effect of clouds forming as the move with the wind as seen when using 3D noise funcitons, but makes it feel a lot more dynamic.

3. The curvature limit can result in overly straight-looking clouds
ScaleThe scale/size of the cloud layer
Density OffsetReducing this value creates more distinct and smaller cloud shapes. Note that for Worley Noise 2 (Slow), this value is typically very small.
CurvatureDetermines how clouds conform to atmospheric curvature.

Higher values create the illusion of the cloud layer being distant when viewed from above (Zenith) and closer when viewed forward (Horizon).

If 2D Clouds are enabled, a cloud curvature greater than 0.6 can cause undesirable stretching along the Y-axis.
ContrastIncreasing this value makes denser cloud areas more pronounced and less dense areas more transparent. Decreasing this value below 1 starts to neutralize the cloud's density.
PersistenceThe rate at which the strength of noise layers making up this cloud layers changes. This controls the level of detail of the cloud layer.
LacunarityThe rate at which the frequency of noise layers making up this cloud layer changes. This also controls the level of detail of the cloud layer.
Wind VectorControls the direction and speed of the cloud layer
LIGHT/COLOR-
Light AbsorptionThe strength at which light is absorbed as it travels through the cloud. Increasing this value would result in the darkening of the denser regions of the cloud layer
Light Absorption PowerControls the concentration/dilution of light absorption based on the cloud's density.
StrengthControls the overall visibility of the cloud
ColorCloud color tint
MASK-
Distance MaskMasks the clouds from the horizon (forward) to the zenith (top). Usually, you might want to mask the cloud layer slightly at the horizon to prevent sharp blending between the sky and the ground.
Distance Blend (Horizon, Min)Controls the sharpenss of the mask at the horizon
Distance Blend (Zenith, Max)Controls the sharpness of the mask at the zenith
DETAIL-
EnabledToggles cloud detail. While this option works for all noise dimensions, it is often used to add dynamism to 2D clouds, as they are inherently static.
Detail WeightControls how strongly the detail noise erodes from the base cloud.
Detail Wind SpeedSets the wind speed for cloud detail, relative to this cloud layer's Wind Vector. A negative value usually produces a more noticeable effect.

Version : 1.0.0