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  1. #1

    Fog Phase Settings (Forward/Backward/Lerp)

    So in the last live stream from the Ubisoft Far Cry Community team I had asked on stream to explain what some of the fog settings do, specifically the fog phase forward, backward and lerp. Its not always obvious and under certain environmental conditions these settings have little effect on the fog/lighting as we saw in the stream. However thanks to Nicolas explanation in the stream I was able to go back into the editor and uncover the mystery behind this settings.

    Well here's a video that should make it pretty clear https://youtu.be/1pu9bh21hXc.

    Basically for the setup I completely removed the terrain with the hole tool, darkened the scene with bottom and top fog with plenty of scattering. Low and behold there are actually 2 light sources that are present in the skybox. The environment we build in (x,y,z axis) is basically 1 massive cube, now imagine that the light being the moon or the sun (which ever is above the horizon or higher than 1/2 the z axis and draw a line originating from the light source (sun or moon) which is the forward light source and extend it through the very center of the environment cube 1/2 x, 1/2 y, 1/2 z and keep going outside of the map cube and you'll hit the backward light source. So notice the sliders I'm adjusting in the video but the phase forward affects the intensity/scatter distance from the moon/sun while the phase backward affects the intensity/scatter distance from the back light source (other end). Meanwhile the lerp is like a fader switch used in DJ equipment to phase out music on input 1 and phase in input 2 or vice versus. If lerp is at a value of .5 which is the mid point then you perfectly balance the effect of phase between the front and back. Not sure if this text is more confusing than anything but after reading it and then watching this video it should become clear.
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  2. #2
    I kinda get it, I guess, but I'm still not sure on the purpose of these controls. As far as I know, the if the sun/moon is not in the sky, it doesn't actually create any light (other than the lens flares if you happen to be able to view under the map through a hole or out an unenclosed tunnel.) You can kinda of bunch up the fog at one end of the sky with them, but does anyone know of any examples where these controls would be good, situations or effects you can create with them?
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  3. #3
    Originally Posted by UnionHouse Go to original post
    I kinda get it, I guess, but I'm still not sure on the purpose of these controls. As far as I know, the if the sun/moon is not in the sky, it doesn't actually create any light (other than the lens flares if you happen to be able to view under the map through a hole or out an unenclosed tunnel.) You can kinda of bunch up the fog at one end of the sky with them, but does anyone know of any examples where these controls would be good, situations or effects you can create with them?
    Well you can use it to setup sunsets (sky effects if kept near the the light source). However you can also use it to create god ray like effects like in this this video https://youtu.be/OjKbfwNlIDY

    Agree if you leave the terrain in tact you will not see the back light source as it’ll be below the terrain but with enough scattering you can still see the effect above the horizon opposite to the side of the map which has the sun/moon. It’s definately a visual polish to maps.
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  4. #4
    Also to get this effect I ended up using the fog phase settings to get the backdrop setup properly

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  5. #5
    Very nice! Thanks for figuring this out!
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  6. #6
    Steve64b's Avatar Senior Member
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    So, if I understand correctly, fog can be seen as a gradient "line" going from your sun/moon through the the center of the map (256,256). In the above picture, Phase Forward would correspond with the blue line, Phase Backward is the red line. Controlling the position of the black dot separating the Forward and Backward sections would be the Lerp (Interpolation)?
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