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 :-)
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] On
Behalf Of André Adam
Sent: 22-Feb-07 12:45
To: 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] 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 |
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