Re: shadow flicker

["Steven Caron" <carons(at)gmail.com>]

file:///C:/Softimage/XSI_5.0/Doc/mental_ray/manual/node76.html#INDEX184

"Values less than 0.05 do not further increase quality in most cases..."

On 6/1/06, Bernard Lebel <3dbernard(at)gmail.com> wrote:

I would definitely use a min of 0 and a max of 3.

Also, what is generally ignored or misunderstood is the treshold. The
treshold color is a control for how sampling is done. Lower values
means that sampling occurs with lower contrasts, in other words, the
level of sampling have more chances of getting closer to the max
value. Higher treshold means a higher contrasts is tolerated before
requiring another level of sampling, so less samples may be takne.

I never work with treshold higher than 0.05, and had to go as low as
0.005 on few occasions. Note that at that point, if the image is
detailed, you should consider ignoring adaptive sampling altogether
and use same min and max values. If the image has significant amounts
of constant colors (like shadow passes, black backgrounds in the
likes), then adapative sampling is still a viable solution.


Lastly, my rule of thumb for the filtering is Gaussian 3/3 for TV
output and Mitchell 4/4 for film output. Gaussian gives a blurrier
sample interpolation, which may "conceal" minor imperfections.



Cheers
Bernard




On 6/1/06, Helen Bucknall <helen(at)helenbucknall.com > wrote:
> Mostly I just use min -1 and max 2. and box filtering 1 or sometimes I
> use triangle 2 for a softer effect.
>
> I output a string of 852 x 480 bmps to my clients and then they mpeg it
> somehow and wack it up on big plasma screens. They never complain. When
> they want stills for print I just render a frame out huge (3000+)but
> leave the antialiasing the same.
> If it's for telly I do HD res. If it's to be comped with live action I
> ask what anti aliasing they want.
>
>
>
> Bernard Lebel wrote:
>
> > Samples 20 is a bit low. I generally put 64 as soon as I set up the
> > shadow map.
> >
> > What do you mean with "standard antialiasing"?
> >
> >
> > Bernard
> >
> >
> >
> >
> > On 5/31/06, Helen Bucknall < helen(at)helenbucknall.com> wrote:
> >
> >> OK. I dragged the spotlight in closer to the scene elements and it seems
> >> to have stopped all the flickering! It wasn't that far away, but now it
> >> is almost close enough to make my character sweaty. I also scaled down
> >> my ground plane a tad.
> >>
> >> Just using 1024 res and sample 20. And bog standard antialiasing.
> >>
> >> So very BIG THANKS to all who replied!
> >>
> >> Joe Laffey wrote:
> >>
> >> > On Wed, 31 May 2006, Helen Bucknall wrote:
> >> >
> >> >> Is there a way to get shadow map shadows to stop flickering even when
> >> >> nothing is moving?
> >> >>
> >> >> This is what I have tried to no avail.
> >> >>
> >> >> On the spot light (cone angle less than 90):
> >> >> Resolution up ( and down).
> >> >> Softness up and down.
> >> >> Samples up.
> >> >>
> >> >> None of these make any diference to the flickering.
> >> >>
> >> >> On the render panel:
> >> >> I've played around with the antialiasing and jitter.
> >> >> On the shadows page I've clicked off rebuild.
> >> >
> >> >
> >> >
> >> > If you view your scene from the light is there an extremely large
> >> > depth to the objects? In other words, are the closest object to the
> >> > light and the farthest object from the light extremely far apart? This
> >> > can lead to ZDepth (used for shadowmaps) presision issues in some
> >> > renderers.
> >> >
> >> > This is often the case if you have a huge ground plane.
> >> >
> >> > You may be able to exclude some objects, to help, or make smaller
> >> > versions that catch shadows.
> >> >
> >> > --
> >> > Joe Laffey                |       Visual Effects for Film and Video
> >> > LAFFEY Computer Imaging   |     -------------------------------------
> >> > St. Louis, MO             |       Show Reel http://LAFFEY.tv/?e01274
> >> > USA                       |     -------------------------------------
> >> > .                         |        -*- Digital Fusion Plugins -*-
> >> >
> >> --------------------------------------------------------------------------
> >>
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