Floor fog with ScatterVolume in Cycles



  • Thank you very much, i greetly appreciate your help.

    Even with your scene at first i could not get the same result as you. It was have because of my settings where in poser native units.

    I had to change to inches, close the scene and reopen it to get your results.

    First fail due to units :
    0_1493633518818_rendu.png

    after inches... Thats it !

    0_1493633477245_success.png
    I think i will keep to inches.



  • @joker Hi, In your shader the P node is not doing anything other than reducing the density.

    Using 0_1493633668071_upload-7d13f238-b090-4114-9351-3aff4744fa9e

    I get

    0_1493633695857_FullFog.png

    and reducing the Y scale, and increasing the X and Z scales on the cube I get

    0_1493633859779_LowFog.png


  • Poser Ambassadors

    I wasn't sure what the U and V nodes do in a volume. So I suggested using the P node for the height, but you're all using the V. So fine, let's look at the V.

    Here is the Poser box, with the surface lit by the V node.

    0_1493635890154_upload-0bb94763-b9ca-413a-9cb9-bb7ac31ac1c7

    Here is the volume lit by the V node.
    0_1493636029713_upload-9b4c120d-d784-4d40-bd7d-3bd29abdcbc0

    Interesting. I would have checked on this yesterday but I didn't have the time. So it would appear that in a surface shader, the V node gives you the V value from the UV mapping, but in a volume shader it can't do that. I expected it would give nothing, but instead it gave something proportional to P.y.

    Guessing that U node would give something proportional to P.x, it seems to do that.

    0_1493636136576_upload-d8884cd5-627d-495d-a2fb-ba3796b171a2


  • Poser Ambassadors

    My problem with the V node, even now that I know it is proportional to P.y, is that I do not know the units, and I won't know them unless I experiment. As I wrote earlier, I do know the units for inches. So if I want to precisely control the gradient, so that as we go up from the ground, the fog begins to diminish at 21 inches and is completely gone at 34 inches, I can easily set that up without experimentation.

    0_1493636638888_upload-a1d0ad96-6566-4133-8369-a6a4e62c1b55


  • Poser Ambassadors

    Now I can, if I like, apply a uniform cloud pattern to the fog like so.

    0_1493636854663_upload-474be3f0-20a3-41b4-badc-bec9da5b8900


  • Poser Ambassadors

    I was going to show how to put all this in a compound node but it wasn't working right. I suspect bugs in compound nodes.

    Anyway - here's a setup involving the modulation of the clouds, so that at the bottom it's solid fog, and then it breaks up from 10 to 40 inches. Above 40 there is nothing.

    0_1493638948254_upload-70008dc3-5bcc-4a55-8aa4-203046408d5b


  • Poser Ambassadors

    Note - you don't have to use emission. I just did so to get the color of fog I wanted as the scatter alone is rather dark.


  • Poser Ambassadors

    Another interesting arrangement is to use the clouds node to modulate the gradient bottom or distance. Here I'm modulating the distance.

    0_1493639466560_upload-905cdde0-0e89-46e9-ac40-c14267161e7b



  • @bagginsbill Wow! Thank you very much. I'm not sure if I've understood everything at the moment, but I am realy happy that I have now the possibility to controll clouds and fog atmospehere effects so good :-)

    I save your explanations. I'm sure I'll can use this very well :-)



  • Thanks, @bagginsbill I knew what you meant about the P node but I couldn't see how to use it to modulate "roughly" on the height, i.e,. not have a uniform fade. Thank you for the explanation I'm sure I will use this! BTW could we not have sub cats here so we could have a sort of Node Cult :o)

    Amanda