After working on the snowman from the holiday scene I decided to do another snow
scene with icicles this time.  Of course, I had to find out how to most
realistically model the shape of an icicle, and found several papers that ended
up providing a pretty good approximate formula.

The image below uses the same texture and isosurface noise functions to model
the snow as I had used for the previous snowman, but with SSLT turned off.  I
attempted to render it with SSLT, and after 9 days it was only 14% complete,
(about half of the roof).  I imagine once it hit the icicles it would stall
completely.  I didn't see enough difference in the part that had completed, so I
killed it.

I am wondering if it would be possible to just turn on SSLT for the snow at the
edge of the roof closest to the camera?

-- Chris R.

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Le 2022-01-20 à 09:36, Chris R a écrit :

> I am wondering if it would be possible to just turn on SSLT for the snow at the
> edge of the roof closest to the camera?
> 
> -- Chris R.

No, unless the edge is a different object than the rest of the snow.
What you can do is to reduce the quality, take less samples.

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Alain Martel <kua### [at] videotronca> wrote:

>
> > I am wondering if it would be possible to just turn on SSLT for the snow at the
> > edge of the roof closest to the camera?
> >
> > -- Chris R.
>
> No, unless the edge is a different object than the rest of the snow.
> What you can do is to reduce the quality, take less samples.


I guess what I'm wondering is if I had a version of the texture (T1) with sslt
enabled, and another version without (T2), and then used

texture {
   gradient x
   texture_map {
      [0.0 T1]
      [0.75 T1]
      [0.75 T2]
      [1.00 T2]
   }
}

Would I get the slowdown from SSLT over the whole object, or just the portion of
the last 25% of the object in the X direction?


-- Chris R.

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Le 2022-01-20 à 13:49, Chris R a écrit :
> Alain Martel <kua### [at] videotronca> wrote:
>> Le 2022-01-20 à 09:36, Chris R a écrit :
>>
>>> I am wondering if it would be possible to just turn on SSLT for the snow at the
>>> edge of the roof closest to the camera?
>>>
>>> -- Chris R.
>>
>> No, unless the edge is a different object than the rest of the snow.
>> What you can do is to reduce the quality, take less samples.
> 
> 
> I guess what I'm wondering is if I had a version of the texture (T1) with sslt
> enabled, and another version without (T2), and then used
> 
> texture {
>     gradient x
>     texture_map {
>        [0.0 T1]
>        [0.75 T1]
>        [0.75 T2]
>        [1.00 T2]
>     }
> }
> 
> Would I get the slowdown from SSLT over the whole object, or just the portion of
> the last 25% of the object in the X direction?
> 
> 
> -- Chris R.
> 
> 
I can't say. It may work. Worth doing some test.

I'd try this :
texture {
    gradient x
    texture_map {
       [0.0 T1]
       [0.74 T1] // avoid a sharp jump between SSLT and non-SSLT
       [0.76 T2] // MAY need a slightly broader overlap in some cases
       [1.00 T2]
    }
}

The slight overlap should hide the change from SSLT to non-SSLT.

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"Chris R" <car### [at] comcastnet> wrote:
> The image below uses the same texture and isosurface noise functions to model
> the snow as I had used for the previous snowman, but with SSLT turned off.  I
> attempted to render it with SSLT, and after 9 days it was only 14% complete,
> (about half of the roof).  I imagine once it hit the icicles it would stall
> completely.


This may be an unworkable suggestion but I'll mention it anyway in case it gives
you another more workable idea - it looks like you're using area lights which
may be a factor in the rendering speed issue. Maybe you can use the light_group
feature to isolate the lighting for the snow from the rest of the scene. If it
works then that would be a major cheat that would make the scene look a little
less realistic but maybe you can minimize the effect somehow. I tried to use
photons with a light_group recently and it didn't work but I haven't tried it
with SSLT.

Kind regards,
Dave Blandston

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