The pixel isn't sampled between 2^2*min and 2^2*max times, but between
2^min and 2^max times. So sampling at 1/1 means 2x2 samples per pixel, not 4x4
like the manual suggests.
2007/2/22, Halfdan Ingvarsson <hingvars(at)softimage.com>:
Mental ray samples on pixel corners but filters from the pixel centre.
With that in mind, the only way to get a non-shifted, non-blurred,
point-sampled image is to render with sampling at 1/1 and using a triangle
filter at 1. This ensures that only the center sample is used in the final
output, with the rest thrown out.
Unfortunately, it is also hideously expensive.
- ½
-----Original Message-----
From: owner-xsi(at)Softimage.COM [mailto: owner-xsi(at)Softimage.COM] On Behalf
Of André Adam
Sent: 22-Feb-07 11:54
To: XSI(at)Softimage.COM
Subject: Re: 16bit Zdepth?
The minimum filter range is 1 pixel (radius), and since the samples are
shot in a one-sample-per-pixel raster, the filter will *always* reach
the neighbouring samples. The trick is to use a filter with a
zero-weight at the maximum extent, like triangle or gauss. Box will have
a 1 weight throughout the whole distance, therefore combining the
original pixel's sample value with the neighbouring ones.
Oh, and I guess the jitter option should be turned off for all of this
to work; haven't tried that, but it should cause problems due to the
need for an even sampling raster (see above).
Cheers!
-André
Daniel Rind wrote:
> It's Sampling at 0 / 0, and filter size at 1 (the minimum).
>
> Each pixel is sampled at least 2^2/min/ times and at most 2^2/max/
> times in each direction.
>
> So for 0 / 0 this means 1 x 1, and for 1 / 1 it would mean 4 x 4, or
> 16 samples per pixel.
>
> The filter /shouldn't/ make any difference, but oddly it does. Box
> filtering adds blur and shifts the whole image down and left by half
> a pixel (really odd), so take triangle filtering.
>
> Ciao, Daniel!
>
>
> 2007/2/22, Tim Leydecker <
BauerOink(at)gmx.de <mailto:BauerOink(at)gmx.de>>:
>
> Hey,
>
> thanks alot guys! I´ve had great success with a
projection
> of a gradient piped into a constant shader and
that one
> assigned the partition (like it simple, the
backroundpartition).
>
> It´s just that rendering bit that puzzles me. To
rinse and repeat,
> I use Filtering set to 0/0, or is it 1/1?
>
> That´s the bit I don´t get, how to make sure I
have no AA at all.
>
> From there it´s still somewhat challenging to get
the correct
> mapping (e.g. linear instead of gamma corrected)
out of XSI
> but that one I should get together by rendering to
float/linear.
>
> I can´t test the above today since I´m still
working in Maya
> but allready do most of my personal stuff in XSI
(at home) it
> would be great to also optimize that in depth once
and for all.
>
> The more I have the chance to compare the apps,
the less
> satisfied I am with Maya, btw. Especially when
shading and
> rendering with passes in mind. Oh, boy.
Additionally, it´s Maya8...
>
> Cheers
>
> tim
>
>
> ----- Original Message -----
> From: "Joe Laffey" < joe(at)laffey.tv <mailto:joe(at)laffey.tv> >
> To: <XSI(at)Softimage.COM
<mailto: XSI(at)Softimage.COM>>
> Sent: Thursday, February 22, 2007 4:18 PM
> Subject: RE: 16bit Zdepth?
>
>
> > On Thu, 22 Feb 2007, Kim Aldis wrote:
> >
> >>> -----Original Message-----
> >>> From: owner-xsi(at)Softimage.COM <mailto:owner-xsi(at)Softimage.COM>
> [mailto:
owner-xsi(at)Softimage.COM <mailto:owner-xsi(at)Softimage.COM>]
On
> >>> Behalf Of Andreas Bystrom
> >>> Sent: 22 February 2007 13:25
> >>> To: XSI(at)Softimage.COM
<mailto:XSI(at)Softimage.COM>
> >>> Subject: Re: 16bit Zdepth?
> >>>
> >>> grab a scalar-state, plug that into a
change_range node and
> finally
> >>> plug the change_range into the
surface port, leave the
> scalar-state
> >>> settings as it is and set the "new
range start" to 0 and "new
> range
> >>> end" to 1 in the change range
node, your old and new-range
> parameters
> >>> should be set to the distance where
you want the depth-pass to
> start
> >>> and end, you can link these 2 values
to nulls with an
> _expression_ and
> >>> use those to control the depth-pass
> >
> >
> >> You may also find that a linear falloff
isn't necessarily what
> you need.
> >> Plugging the output of the change range
into a grad will allow
> you to tweak
> >> it, if you need to.
> >>
> >
> > I think the non-linear mapping would be
better done in the
> compositor, though. That
> > way you have the option of linear or putting
a curve on it.
> >
> > --
> > Joe
Laffey |
Visual Effects for Film and Video
> > LAFFEY Computer Imaging |
> -------------------------------------
> > St.
Louis, MO
| Show Reel http://LAFFEY.tv/?e04685
> > USA
|
> -------------------------------------
> >
.
| -*- Digital Fusion Plugins -*-
> >
>
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