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New Sky Rendering Mission Parameters


The new sky is rendered as five separate components: sky, stars, celestial object, distant art, and clouds. When the new sky is enabled, the remaining components may be optionally switched on or off. If the new sky is NOT enabled, then the old-style sky rendering will occur.

Here is each component, and an explanation of the mission parameters.


NewSky:SkyEdit

Some quick info. The sky is rendered as a sort of dome around the camera. If the camera were at the center of this dome, then all points in the sky would be equidistant from the camera, and fog would be applied equally to all points in the sky. This would suck. As a solution, we render the sky as a dome, but with the camera offset from center - up toward the edge of the dome. When we do this, the parts of the sky directly above are close, when those on the horizon are far, which gives us a nice fog.

Sometimes, latitude and longitude angles are specified. Longitude angles stars at +x, and move counter-clockwise to +y. Latitude angles start at the pole (directly above camera), and move down to the horizon at 90 degrees.

When in game mode, a useful console command is "sky_dump". It spits out how many sky points are computed, and how much total memory is used.

"Enable New Sky" When enabled, the new-style sky is rendered, and all other new-style components become available.

"Enable Fog" When enabled, any fog defined for the mission is applied to the sky.

"Atmosphere radius" The radius, in feet, of the sphere that represents the sky, with "earth" at the center. Must be greater than 0.

"Earth Radius" The radius of the "earth", in feet. In other words, the offset from center where the camera is. The closer this number is to "Atmosphere radius", the less sky directly above is fogged. This number should always be less than "Atmosphere radius". Must be greater than 0 and less than atmosphere radius.

"# of latitude points" Designers scale the complexity of the sky rendering. The more points that represent the sky, the better it will look, but at the cost of memory and framerate. This value represents the number of latitudinal lines (east/west) represented in the sky. Image a globe, with its lats and longs, viewed from the inside. This is our model of the sky, and the North pole is always pointing straight up. Must be at least 3.

"# of longitude points" The number of longitudinal lines (north/south, though the poles). Must be at least 3.

"Horizon dip angle" We don't want to render the sky in a complete sphere around the camera, since at best, about 40% of it would never be seen, due to the ground beneath our feet. So, we define how far down the horizon goes, in degrees. This may vary from level to level. The trick is that we don't want the horizon too "high" - if the player can see into that region, he'll see whatever was rendered in the previous frame - making trippy ghost trails, etc. The dip angle is a latitude angle, and should be some value greater than 90. Must be at least 90.

"Pole color" The overall color of the sky is specified by using five control points - different latitude angles. The "pole" is the color of the sky directly above, and is specified as a set 0-1 rgb values, where 0 is black, and 1 is white.

"45 degree color" Color of sky at this latitude.

"70 degree color" Color of sky at this latitude.

"Horizon color" Color of sky at horizon (90 degree latitude).

"Horizon dip color" Color of sky past 90 degrees.

"Glow color" In addition to the overall sky color (which is symmetrical around the pole), the designer can specify a "glow" region in the sky. The color specified here is factored into the sky color based on the "method", as specified below.

"Glow latitude" Latitude, where glow is centered.

"Glow longitude" Longitude where glow is centered.

"Glow angle" Total angular size, in degrees, of the glow.

"Glow scale" Multiplier on glow. 1 means full glow. 0 means none.

"Glow method" This can be "Sum" or "Interpolate". If "Sum", then light from the glow is "added" into the sky color, so that a blue sky plus a red glow would make a purple sky. If "Interpolate", then a blue sky would be replaced by a red glow, as if it were an overlay.

"Clip latitude" This is an optimization value. If non-negative, this degree angle says below which angle sky is not to be rendered. For example, if you have an opaque cloud deck that totally obscurs the sky, you may want only the horizon to render, so you'd set the angle to something like 80 degrees (90 degrees is horizon, 0 degrees is pole).


NewSky:StarsEdit

The new stars are real stars! I randomly chose midnight, at winter, at a latitude of 42 degrees. They are affected by the intensity of the sky color at its position of the sky, so that if the sky is dark above, but light at the horizon, the stars will become more dim toward the horizon.

"Enable Stars" If the new sky is enabled, and this is enabled, new stars will be rendered.

"Enable Fog" If enabled, stars will fog.

"Star Density" A 0-1 value. If 1, you can expect around 800-900 stars in the sky. Lesser values weed out lower-intensity stars.

"Star Offset" A value in feet, this says how much closer stars are to the camera than the sky. A value of 0 is just fine, but larger values will place stars closer, and so will fog less than the sky.

"Max Sky Intensity" A 0-1 value. This says how the apparent brightness of a star is affected by the intensity of the sky. The intensity of the sky is simply the largest color component (r,g, or b) on a 0-1 scale. When a star is rendered in a part of the sky whose intensity is greater than "Max Sky Intensity", the star will not be seen. As the intensity becomes lower, the star will appear brighter.


NewSky:Celestial(1,2,3)Edit

Currently, we support only three celestial objects, but we could add more if need be. A celestial object is expected to be something like a sun or a moon. 8-bit art is expected. Typically, a sun will be an alpha texture, and the moon will be a transparent one.


"Enable Celestial object" When enabled, and the new sky is enabled, will render the celestial object.

"Enable Fog" When abled, will apply fog to the celestial object.

"Is Alpha Texture" If specified, will treat the texture as a monochromatic alpha texture, where index 0 is transparent, and index 15 is opaque.

"Texture" Name of the texture that lives in fam\skyhw.

"Alpha" Overall alpha level of the texture. If 1, will be opaque; 0 is invisible. Using a non-1 value may be desired, for example, to make a daytime moon blend into the sky.

"Celestial Offset" Like stars, this value, in feet, says how much closer the celestial object is to the camera than the sky is. This will affect how the object gets fogged.

"Angular Size" In degrees, how large the object is in the sky.

"Latitude" Latitudinal angle of the object.

"Longitude" Longitudinal angle of the object.

"Rotation" Rotation angle of the object around its center, so a designer can make a crescent moon face the way desired.

"Color" 0-1 rgb values applied to the object - to make the sun yellow, or moon a dark orange, or whatever.


NewSky:DistantArtEdit

This renders a distant scene around the camera - like if you want to be surrounded by mountains or buildings.


"Enable Distant Art" Enables the rendering of distant art.

"Enable Fog" If enables, will fog based on the distance from camera.

"Texture #1" The texture to apply

"Texture #2" If specified, alternates with Texture#1. Serves to add variation to horizon art.

"Color" The color to be applied to the texture

"Distance" The distance from camera, in feet, the art is. Must be greater than 0.

"Top Latitutde" The latitude angle, in degrees, that says where the top of the "panels" are. Must be a positive value.

"Bottom Latitutde" The latitude that specifies where the bottom of the "panels" are. Must be positive, and greater than top.

"# of panels" How many art panels there are in the circle around the camera. Must be greater than 2.

"# of panels/texture" How many panels are in the texture. This number should divide evenly into the number of panels. Must be greater than 0.

"Alpha" The overall alpha level of the art.


NewSky:CloudsEdit

Clouds are rendered as a grid of tiles, at a fixed altitude.

When in game mode, a useful console command is "cloud_dump". It spits out how many grid points are computed, and how much total memory is used.


"Enable Cloud Deck" Set to enable the cloud deck.

"Enable Fog" Set to allow the deck to be fogged.

"Alpha Texture" Set if cloud texture is an alpha texture.

"Texture" The texture name.

"Alpha" The overall alpha level of the cloud deck.

"Height" The altitude of the cloud deck, in feet.

"Tile size" The size, in feet, of a cloud tile. Tiles are square. This number is the length of one of the sides. This must be some value greater than 0.

"Tiles per side" Number of tiles, on a side, in the "grid". For any number 'n', the number of tiles in the grid is n*n. This must be at least 1.

"# subtiles" How many subtiles are within a tile, on a side. For example, for some number 'n', there are n*n subtiles. Use subtiles to improve fogging and lighting of the cloud deck. This must be at least 1.

"Wind velocity" The direction and speed of the wind. 'z' is ignored.

"Overall color" Overall color of the cloud deck, on a 0-1 rgb scale.

"East color" The color of the deck toward the east, 0-1 rgb scale.

"East color method" The method by which color is added to the cloud deck. 'Interpolate' will move from specified color to overall cloud deck color. 'Sum' will add in the color's contribution.

"East scale" The degree to which the color is added in.

"West color" The color of the deck toward the west, 0-1 rgb scale.

"West color method" The method by which color is added to the cloud deck. 'Interpolate' will move from specified color to overall cloud deck color. 'Sum' will add in the color's contribution.

"West scale" The degree to which the color is added in.

"East/West rotation" Defines where east and west are. This is an angle in degrees.

"Subtile alpha start" Defines how many subtiles from edge of grid the cloud deck should start to fade into the sky.

"Glow color" The glow color, 0-1 rgb scale.

"Glow color method" The method by which color is added to the cloud deck. 'Interpolate' will move from specified color to overall cloud deck color. 'Sum' will add in the color's contribution.

"Glow scale" The degree to which the color is added in.

"Glow latitude" The latitudinal angle, in degrees, where the glow originates.

"Glow longitude" The longitudinal angle, in degrees, where the glow originates.

"Glow angle" The size of the glow in the sky, in degrees. If you want there to be no glow, set this to 0 or less.

"Glow tiles" How many tiles there are, on a side, within each subtile, around the glow. This serves to add more resolution to the glow area. Be warned that this can potentially greatly increase the number of points in the clouds, depending on the number of subtiles within the glow. This must be at least 2 to take effect.

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