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The Env Sky texture is an environment map that generates images of a planetary atmosphere as seen from the surface of a planet.

Sky attributes let you control the composition of the atmosphere and the cloud layer. If no floor is specified, the environment below the horizon is a vertical mirror reflection of the environment above the horizon. If you specify a floor, you can set it to a color or use a texture map.

If a floor is specified and the camera point-of-view drops below that floor, then the sky will turn red as a warning.

You can use the Env Sky texture as a reflection map, by connecting its Out Color attribute to the Reflected Color attribute of an specular shader, such as Blinn or PhongE. You can also use the Env Sky texture as a background, by connecting it to an image plane. For best results, scale the sky so it is in proportion to the half-height of the image plane.

Aside from the attributes listed here, Env Sky inherits additional attributes from TextureEnv.

In the table below, important attributes have their names listed in bold in the description column.

Node nameParentsClassificationMFn typeCompatible function sets
envSkytextureEnvtexture/environment:drawdb/shader/environment/envSkykEnvSkykBase
kNamedObject
kDependencyNode
kTextureEnv
kEnvSky

Related nodes

layeredTexture, envCube, envSphere, envBall, envChrome, bump3d, uvChooser, bump2d, texture2d, ramp, file, cloth, water, stencil, checker, fractal, bulge, grid, mountain, texture3d, projection, cloud, granite, crater, leather, stucco, brownian, solidFractal, marble, wood, rock, snow, defaultTextureList, place2dTexture, place3dTexture

Attributes (53)

The following quick index only shows top-level attributes (too many attributes to show them all): airDensity, altitude, azimuth, blur, cloudBrightness (3), cloudSamples, cloudTexture, density, dustDensity, elevation, floorAltitude, floorColor (3), floorSamples, haloBrightness (3), haloSize, hasFloor, pointCamera (3), power, refPointCamera (3), size, skyBrightness (3), skyRadius, skySamples, skyThickness, sunBrightness (3), sunsetBrightness (3), threshold, totalBrightness, useTexture

Long name (short name)TypeDefaultFlags
airDensity (ad) float1.0outputinputconnectablestorablekeyable
Air Density controls how light is scattered by the atmosphere, and therefore the "blueness" of the sky. To simulate high-altitude skies (which are black at the zenith, and blue near the horizon), set Air Density to values less than 1.0. To simulate low-altitude skies (which are blue at the zenith, and white near the horizon), set Air Density to values greater than 1.0.
altitude (a) float0.2outputinputconnectablestorablekeyable
Altitude controls the apparent altitude of the cloud layer. This does not affect the position of the clouds on the screen. Rather, it affects the fraction of the atmosphere that obscures the clouds near the horizon. Low-altitude clouds disappear into haze much more slowly than high-altitude clouds.
azimuth (az) angle (double)145.0degoutputinputconnectablestorablekeyable
Azimuth controls the position of the sun around a vertical axis. Adjust this to move the sun around horizontally without changing its elevation.
blur (b) float1.0outputinputconnectablestorable
Blur controls the size (radius) of the halo around the sun.
cloudBrightness (cb) float30.5, 0.5, 0.5outputinputconnectablestorable
Cloud Brightness sets the brightness of the ambient scattered light from the atmosphere. This also depends on the current Elevation of the sun.
cloudBrightnessR (cbr) float0.0outputinputconnectablestorablekeyable
The red component of Cloud Brightness
cloudBrightnessG (cbg) float0.0outputinputconnectablestorablekeyable
The green component of Cloud Brightness
cloudBrightnessB (cbb) float0.0outputinputconnectablestorablekeyable
The blue component of Cloud Brightness
cloudSamples (csa) float5.0outputinputconnectablestorable
Cloud Samples controls the number of "samples" that the renderer uses in its calculations of the clouds. You can decrease this value to speed up the environment calculation, but if you do so, you will lose some of the atmospheric effects --- clouds will not fade to mist at the horizon.
cloudTexture (ct) float1.0outputinputconnectablestorablekeyable
Cloud Texture lets you assign a layer of clouds to the sky. Map a Cloud texture or other fractal texture to this attribute.

Note: if you use this attribute, you must turn on the Use Texture attribute, or you will not see your clouds.

density (d) float1.0outputinputconnectablestorable
Density controls how dense the clouds are. At 0.0, the clouds are non-existent. Increase the value to make the clouds denser. At 5.0, they are heavy rain clouds.
dustDensity (dd) float0.0outputinputconnectablestorablekeyable
Dust Density density of the dust in the atmosphere.
elevation (e) angle (double)45.0degoutputinputconnectablestorablekeyable
Elevation controls how high the sun is in the sky. An elevation of 0 degrees would put the sun at the horizon, and an elevation of 90 degrees would put it directly overhead.
floorAltitude (fa) float-10.0outputinputconnectablestorable
Floor Altitude controls the position of the floor plane relative to the vertical axis. Increase this to move the floor up, decrease it to move the floor down. Remember to always keep your camera above the floor altitude.
floorColor (fc) float30.4, 0.4, 0.4outputinputconnectablestorable
Floor Color controls the color of the floor, when Has Floor is turned on. You can, of course, texture map this attribute to get interesting ground effects.
floorColorR (fcr) float0.0outputinputconnectablestorablekeyable
The red component of Floor Color
floorColorG (fcg) float0.0outputinputconnectablestorablekeyable
The green component of Floor Color
floorColorB (fcb) float0.0outputinputconnectablestorablekeyable
The blue component of Floor Color
floorSamples (fsa) float1.0outputinputconnectablestorable
Floor Samples controls the number of "samples" that the renderer uses in its calculations of the floor. You can decrease this value to speed up the environment calculation, but if you do so, you will lose some of the atmospheric effect along the floor (i.e. fading towards the horizon).
haloBrightness (hb) float30.5, 0.5, 0.5outputinputconnectablestorable
Halo Brightness controls how bright the halo around the sun is. Note: this attribute only affects the brightness of the halo, and not its color.
haloBrightnessR (hbr) float0.0outputinputconnectablestorablekeyable
The red component of Halo Brightness
haloBrightnessG (hbg) float0.0outputinputconnectablestorablekeyable
The green component of Halo Brightness
haloBrightnessB (hbb) float0.0outputinputconnectablestorablekeyable
The blue component of Halo Brightness
haloSize (hs) float20.0outputinputconnectablestorablekeyable
Halo Size controls the radius over which direct back-lighting from the sun occurs. This is most noticeable near the edges of thick clouds or anywhere on thin clouds.
hasFloor (hf) booltrueoutputinputconnectablestorable
Has Floor controls whether there is a floor in the environment. If you turn this off, the environment below the horizon is a mirror reflection of the environment above the horizon.
pointCamera (p) float30.0, 0.0, 0.0outputinputconnectablehidden
The current sample point that has to be shaded
pointCameraX (px) float0.0outputinputconnectablehidden
The x component of the current sample position
pointCameraY (py) float0.0outputinputconnectablehidden
The y component of the current sample position
pointCameraZ (pz) float0.0outputinputconnectablehidden
The z component of the current sample position
power (po) float1.0outputinputconnectablestorable
Power scales and positions the clouds. If you set Power to 0, you will get clouds that have little or no variation in density within each cloud. As you increase Power, you will see more variation. (Basically, Power acts to modulate the Density attribute.)
refPointCamera (rpc) float30.0, 0.0, 0.0outputinputconnectablehidden
The current reference sample point that has to be shaded
refPointCameraX (rcx) float0.0outputinputconnectablehidden
The x component of the current sample position
refPointCameraY (rcy) float0.0outputinputconnectablehidden
The y component of the current sample position
refPointCameraZ (rcz) float0.0outputinputconnectablehidden
The z component of the current sample position
size (sz) float0.531outputinputconnectablestorable
Size controls the size (radius) of the disk of the sun.
skyBrightness (sk) float30.5, 0.5, 0.5outputinputconnectablestorable
Sky Brightness is a color value that is multiplied by the basic sky color. You can use this to brighten or darken or tint the sky.
skyBrightnessR (skr) float0.0outputinputconnectablestorablekeyable
The red component of Sky Brightness
skyBrightnessG (skg) float0.0outputinputconnectablestorablekeyable
The green component of Sky Brightness
skyBrightnessB (skb) float0.0outputinputconnectablestorablekeyable
The blue component of Sky Brightness
skyRadius (sr) float50.0outputinputconnectablestorable
Sky Radius can be thought of as the size of the planet, epressed as a multiple of Sky Thickness. When you increase this, it affects the relative difference in light scattering between light coming from above and light coming from the horizon. The bigger the planet, the more sunlight has to go through as the sun sets.

Effectively, increasing this value will result in redder but dimmer sunsets. (You can compensate for dimness by increasing the Sky Brightness)

skySamples (ssa) float5.0outputinputconnectablestorable
Sky Samples controls the number of "samples" that the renderer uses in its calculations above the cloud layer. You can decrease this value to as low as one to speed up the environment calculation. However, decreasing it too much may result in undesirable "flatness" in the image, and loss of detail.
skyThickness (st) float1000.0outputinputconnectablestorable
Sky Thickness controls the thickness of the atmosphere. When this is increased, light has to pass through more air, and is therefore scattered more, showing more color.
sunBrightness (su) float30.5, 0.5, 0.5outputinputconnectablestorable
Sun Brightness controls how bright the sun is in the environment. Note: this attribute only affects the brightness of the sun, and not its color.
sunBrightnessR (sur) float0.0outputinputconnectablestorablekeyable
The red component of Sun Brightness
sunBrightnessG (sug) float0.0outputinputconnectablestorablekeyable
The green component of Sun Brightness
sunBrightnessB (sub) float0.0outputinputconnectablestorablekeyable
The blue component of Sun Brightness
sunsetBrightness (ss) float31.0, 1.0, 1.0outputinputconnectablestorable
Sunset Brightness controls the illumination of the clouds when the sun is below the horizon and the clouds are front-lit. This is a very subtle effect and only occurs briefly after sunset.
sunsetBrightnessR (ssr) float0.0outputinputconnectablestorablekeyable
The red component of Sunset Brightness
sunsetBrightnessG (ssg) float0.0outputinputconnectablestorablekeyable
The green component of Sunset Brightness
sunsetBrightnessB (ssb) float0.0outputinputconnectablestorablekeyable
The blue component of Sunset Brightness
threshold (t) float0.5outputinputconnectablestorable
Threshold controls how much of the sky is covered with cloud. At 0.0, the entire sky will be cloudy. As this value increases, you will see more and more of the sky through the cloud layer.
totalBrightness (tb) float1.0outputinputconnectablestorablekeyable
Total Brightness controls the overall brightness level of the environment.
useTexture (ut) boolfalseoutputinputconnectablestorable
Use Texture controls whether or not Env Sky pays attention to the Cloud Texture attribute. If you attach a Cloud or other fractal texture node to the Cloud Texture attribute, then you must turn on Use Texture to see the results.