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  1. #17041
    Member Ace Dragon's Avatar
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    I honestly don't know if you really want to use Random Walk as the solution to clouds.

    While it is the most accurate SSS algorithm ever created, I don't think it's to the point where light can exit the object and illuminate elements on the other side (which is kind of an important thing for clouds).
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  2. #17042
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    Originally Posted by Ace Dragon View Post
    I honestly don't know if you really want to use Random Walk as the solution to clouds.

    While it is the most accurate SSS algorithm ever created, I don't think it's to the point where light can exit the object and illuminate elements on the other side (which is kind of an important thing for clouds).
    As I understand it - random walk SSS doesn't currently include anisotropy.

    Anisotropy is very important in some clouds (see Mie scattering)



  3. #17043
    Random walk SSS assumes hard diffuse boundaries, and a fixed volume density inside the mesh. With that assumption we can sample light only at the exit point and not do any ray marching of the density field.

    For volumes like clouds there is no clear exit point, there's only soft boundaries. However there is an optimization which is a bit similar that I would like to add, which would be to sample light less often when we are estimated to be deeper inside the volume. In this case "inside" and "outside" are not strictly defined, and you could still have light coming from inside the volume (e.g. fire), but something could be figured out.

    Ray marching through the density field is always going to be slower than assuming a fixed density everywhere, though some optimizations in this area are possible as well.

    I don't think you will get realistic looking clouds with random walk SSS, but for some stylized look it could be useful.



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