POV-Ray : Newsgroups : povray.binaries.images : Happy Holidays : Re: Happy Holidays Server Time
19 Jun 2024 18:23:56 EDT (-0400)
  Re: Happy Holidays  
From: Chris R
Date: 16 Dec 2021 12:20:00
Message: <web.61bb74f7a9b6fbbcce7c8a215cc1b6e@news.povray.org>
"Chris R" <car### [at] comcastnet> wrote:
> Cousin Ricky <ric### [at] yahoocom> wrote:
> > On 2021-12-15 5:10 PM (-4), Chris R wrote:
> > >
> > > Looking at the picture in detail, I was unhappy with the way the puddle melting
> > > off of the snowman looked.  ...
> >
> > I didn't comment on the snowman before, because I didn't know if you
> > wanted it to be real snow. But now that I see that it's melting, I have
> > a couple of suggestions.
> >
> > First off, the diffuse value needs to be higher, close to 1.0.  And if
> > you are *not* using radiosity, the ambient value needs to be scaled up
> > proportionately.
> >
> > Second, snow really needs SSLT.  Of course, this will slow down the
> > render even more.  If you prefer to finish rendering by February, you
> > can cheat by adding a bit of emission to the snow in lieu of SSLT; I
> > once abused the ambient keyword this way to get a subsurface effect on
> > some beach balls.  If you cheat in this manner, then you may have to
> > take the diffuse below 1.0 to compensate for the "glow."
> >
> > Otherwise, the scene looks great!
>
> Thanks for the suggestions.  I keep waffling on whether to make the snow more
> realistic or not.  The scene is a bunch of ornaments, so the melting snowman is
> meant to be a bit of humor, but I had also considered making him a real snowman
> who just happens to have wandered into the scene.  I'll try some of your
> suggestions as I can see other uses for having a good model for snow.
>
> -- Chris R

I started playing around with subsurface in the finish for the snowballs.  After
fiddling with settings I could get some very convincing looking ice-balls, but
I'm not sure how to get it to look more like snow.

A few other things I noticed in my experiments:
 - Using subsurface dampens the effects of any normals in the texture pretty
dramatically.  This isn't too much of an issue since my snowballs are
isosurfaces and I can just translate the normals into perturbations on the
sphere shape.  I assume that's a known effect due to the subsurface algorithm,
it just surprised me.
 - There is an interaction between the diffuse setting in the finish and
subsurface.  I found if diffuse is too high, I get a very weird, reflective
surface.  I wonder if this is related to the caveats in the wiki about
zero-values in colors used for subsurface, or if it's some undocumented
interaction.

-- Chris R


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