Re: 16bit Zdepth?

["Tim Leydecker" <BauerOink(at)gmx.de>]

Besides using the depthchannel as a way to create some subtile
lighting (in it´s most simply way, some percentages of screen)
out of the camera axis - which is great to give a "flashy" look,
I use the depthchannel (sofar) mostly for Frischluft Lenscare,
without AA but at double the resolution of the other passes rendered
and at 16bit to get as few artifacts as possible. Phillip Spoeth also
has some rudimentary postlighting tool (ZBornToy) I haven´t used
yet for more than fiddling with the demo but that has still proven
it is very, very sensitive to the type and mapping of the Z-channel.

Geared mostly towards finishing the look of ZBrushstuff for stills
(I guess that at least - from Taron´s involvement) it´s still likely
the closest to what I could get to as for using a post lighting tool.

That´s one of the reasons I got intrigued about how to do depth best
but it´s also that I currently evaluate (my own speed) with Maya and
XSI - trying to figure which is the better tool for the stuff I tend to do.

Ideally, you´re right, it´s no hassle at all, you pick Zdepth as a buffer,
specify the targetformat and bitdepth and forget about it, post´ll do it...

But it´s just proven not that simple, as can been seen when even
Halfdan has to pause a moment in memorizing which AA suits best.
It´s those little things that work flawlessly that make or break a deadline...

Cheers

tim



----- Original Message ----- 
From: "Daniel Rind" <daniel.rind(at)gmail.com>
To: <XSI(at)Softimage.COM>
Sent: Saturday, February 24, 2007 12:00 AM
Subject: Re: 16bit Zdepth?


Well, what's wrong with just enabling the depth render channel? It's
practically free unless you explicitly want to render only the depth channel
and no color output (but what would you want with that?).

Ciao, Daniel!


2007/2/23, Tim Leydecker <BauerOink(at)gmx.de>:
> Coming back to the original question (even thought my head aches, too).
>
> How about the Softimage renderer? Given that mR is not so effective
> when trying to render without any AA, how´s the old renderer doing?
>
> I know, I´m not supposed to mention M**a again and again, it´s just
> that I (finally) realized it has this other software renderer that is
> really
> fast without AA. I´m currently rendering Tif16 (as suggested) using
> a ramp/gradient projection perpendicular and attached to the camera.
>
> Is simple enough and it works quite well to modulate the gradient to
> have the fallof desired, e.g. either linear or more exponential, in case
> one would directly want to (not accurately) mimic different focal lengths
> and their expected sharp zone (fallof). I´m just using linear to play
> later, tho...
>
> Cheers
>
> tim
>
>
> ----- Original Message -----
> From: "André Adam" <a_adam(at)49games.de>
> To: <XSI(at)Softimage.COM>
> Sent: Friday, February 23, 2007 9:18 AM
> Subject: Re: 16bit Zdepth?
>
>
> > Now, that was my setup yesterday, except for the beer exchanged with
> Gin-Tonic.
> > Ahh, where is that box of Aspirin when you really need it...
> >
> > ;)
> >
> >
> > Halfdan Ingvarsson wrote:
> >>
> >> Low lights, smoky room, and a pint of beer.
> >>
> >>
> >>  - ½
> >>
> >>
> >>
> ------------------------------------------------------------------------
> >>
> >> *From:* owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] *On
> Behalf Of
> >> *Kris Rivel
> >> *Sent:* 22-Feb-07 13:47
> >> *To:* XSI(at)Softimage.COM
> >> *Subject:* Re: 16bit Zdepth?
> >>
> >>
> >> You are all going to be dreaming of samples tonight if this thread
> >> continues....ugh.  Look, I just want to know one thing.......what
> setting makes my
> >> render look best :-)
> >>
> >> Kris Rivel
> >> 3D Artist
> >> kris(at)krisrivel.com <mailto:kris(at)krisrivel.com>
> >> www.krisrivel.com <http://www.krisrivel.com>
> >>
> >>
> >>
> >> André Adam wrote:
> >>
> >> The if(allsamples=0){} idea is a good explanation why both mechanisms
> seem to
> >> work. Thanks for the input! :)
> >>
> >>    -André
> >>
> >>
> >> Halfdan Ingvarsson wrote:
> >>
> >> A) Triangle filter of size 1 will have zero weights on the edges. So in
> the case
> >> of 1/1 samples, the middle sample will have a weight of 1.0 while the
> rest (which
> >> are all on the edges of the pixel) will have a weight of 0.0. Therefore
> the middle
> >> pixel is the only one sampled.
> >>
> >> B) I'm guessing from the couple of tests that I did that in the case of
> a combined
> >> weight of zero over all samples covered by the filter, mental ray will
> simply pick
> >> a single, unweighted sample to use. Possibly, the lower-left pixel
> sample. In this
> >> case the image shifts, compared to the center-sample case.
> >>
> >> The filter is always rectangular, not elliptical.
> >>
> >>  - ½
> >>
> >>
> >> -----Original Message-----
> >> From: owner-xsi(at)Softimage.COM <mailto:owner-xsi(at)Softimage.COM>
> >> [mailto:owner-xsi(at)Softimage.COM] On Behalf Of André Adam
> >> Sent: 22-Feb-07 12:45
> >> To: XSI(at)Softimage.COM <mailto:XSI(at)Softimage.COM>
> >> Subject: Re: 16bit Zdepth?
> >>
> >> That doesn't seem to work for my logic; what happens when rendering
> Sampling 0/0
> >> with a Triangle or Gauss Filter set to 1?
> >>
> >> A) If the filter size is a radius in pixel length, and the filter works
> from the
> >> pixel's center rather from than the corners, then four samples will be
> hit by the
> >> filter. Five in case of a Sampling 1/1. Should therefore show an aa
> effect.
> >>
> >> B) If the filter size is a diameter in pixel length, and the filter
> works from the
> >> pixel's center rather than from the corners, while four samples are hit
> by the
> >> filter, all of their values are multplied by a zero weight and the
> result should
> >> be a pitch black picture. Certainly doesn't work this way.
> >>
> >> Looking at the empirics, I get perfectly non-aa pictures with both
> techniques,
> >> sampling 1/1 and sampling 0/0 combined with either triangle or gaussian
> filter set
> >> to 1. Though the pictures differ a bit.
> >>
> >> What's the missing piece in the puzzle now? :)
> >>
> >> Cheers!
> >>
> >>     -André
> >>
> >>
> >> Halfdan Ingvarsson wrote:
> >>
> >> 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>
> >> [mailto:owner-xsi(at)Softimage.COM] On Behalf Of André Adam
> >> Sent: 22-Feb-07 11:54
> >> To: XSI(at)Softimage.COM <mailto: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>
> >> <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>
> >> <mailto:joe(at)laffey.tv> >
> >>     To: <XSI(at)Softimage.COM <mailto: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 <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>
> >> <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 -*-
> >>     >
> >>
> --------------------------------------------------------------------------
> >>
> >>     > Mail here will be rejected --> "Real Trap" <
> >>
> >
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