Re: 16bit Zdepth?

["Daniel Rind" <daniel.rind(at)gmail.com>]

Docs say:

 

Each pixel is sampled at least 2^2min times and at most 2^2max times in each direction.

The "in each direction" is new I think, that wasn't always there. I guess it's a typo.

 

Ciao, Daniel!

 

2007/2/22, Halfdan Ingvarsson <hingvars(at)softimage.com>:

Not quite. It's 2^max samples on a side, or in other words: 2^max * 2^max == 4^max == 2^(2*max)

 

Pretty pictures: http://lamrug.org/resources/samplestips.html

 

 - ½

 

---

From: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] On Behalf Of Daniel Rind
Sent: 22-Feb-07 12:06

To: XSI(at)Softimage.COM
Subject: Re: 16bit Zdepth?

 

Heh yeah, true.

 

Also means that the mental ray docs are wrong.

 

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.

 

Ciao, Daniel!

 

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.
>
>