 | | | Elliptical filtering | Elliptical filtering 2005-05-31 - By Brad Friedman
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IC. re-reading the mental ray docs on the subject in the context of
your answer, it kinda makes sense now. The word "pyramid" is used
quite a bit in the description of the filtering method but I honestly
think it would be worth them mentioning that not only does the filter
work in terms of a pyramid (geometrically speaking) but actually makes
use of a pyramid texture lookup directly. So, precomputed pyramid
textures can speed up both elliptical and pyramid filtering. I had no
idea this was the case previously. I had assumed the elliptical filter
was always reading level 0.
Therefore, I had always turned to using simple pyramid filtering by
turning on the "Enable Multi-Resolution Texture" option in the image
source and left it at that. Unless things were so bad with filtering
that even mip mapping didn't take care of it with some blurring tweaks,
then I'd turn to elliptical. Now I should rethink that strategy.
Thanks.
-brad
Bernard Lebel wrote:
>Brad: elliptical filtering is necessary to take advantage of the
>multi-resolution of the pyramidal map file. Otherwise the maximum
>resolution is always the one lookedup by mental ray (thus more
>memory).
>
>Alan: I also suspect network issue, although as you said, such a
>dramatic increase in render time is quite strange.
>
>
>Bernard
>
>
>On 5/31/05, Alan Jones <skyphyr@(protected)> wrote:
>
>
>>Maybe with that render time a lot of it's reading the files off the
>>disk? Pulling the .pic into memory then uncompressing it within memory
>>may be signicantly faster. Though I wouldn't expect it to make such a
>>huge difference.
>>
>>That's the only guess that comes to mind though sorry.
>>
>>Cheers,
>>
>>Alan.
>>
>>On 5/31/05, Brad Friedman <xsibrad@(protected)> wrote:
>>
>>
>>>This is a question more than an answer:
>>>
>>>Why convert to pyramid if you're going to use elliptical filtering? I
>>>thought the two were entirely different types of filters. Or can
>>>elliptical filtering take advantage of a pyramid texture?
>>>
>>>-brad
>>>
>>>Bernard Lebel wrote:
>>>
>>>
>>>
>>>>Hi,
>>>>
>>>>I am baffled at something. I have a scene with rather large textures
>>>>(3500x3500 and higher). In Pic format, it renders in 45 seconds.
>>>>
>>>>So I'm looking to save render time, and memory while we're at it, so I
>>>>convert textures to pyramidal map float files (imf_copy -p [...] map
>>>>rgba_fp).
>>>>Then I turn on elliptical filtering, set the Maximum Pixels for
>>>>Minimum Radius to a low value 1.3, because higher than that is
>>>>generally not necessary.
>>>>
>>>>In the past, I got much faster render times. However right now the
>>>>render time explodes: it's at least 5 times longer than with the Pic
>>>>version.
>>>>
>>>>Any idea?
>>>>
>>>>
>>>>Thanks
>>>>Bernard
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IC. re-reading the mental ray docs on the subject in the context of
your answer, it kinda makes sense now. The word "pyramid" is used
quite a bit in the description of the filtering method but I honestly
think it would be worth them mentioning that not only does the filter
work in terms of a pyramid (geometrically speaking) but actually makes
use of a pyramid texture lookup directly. So, precomputed pyramid
textures can speed up both elliptical and pyramid filtering. I had no
idea this was the case previously. I had assumed the elliptical filter
was always reading level 0.<br>
<br>
Therefore, I had always turned to using simple pyramid filtering by
turning on the "Enable Multi-Resolution Texture" option in the image
source and left it at that. Unless things were so bad with filtering
that even mip mapping didn't take care of it with some blurring tweaks,
then I'd turn to elliptical. Now I should rethink that strategy.<br>
<br>
Thanks.<br>
<br>
-brad<br>
<br>
Bernard Lebel wrote:
<blockquote cite="mid61d0e2b40505311409484cd5ce@(protected)"
type="cite">
<pre wrap="">Brad: elliptical filtering is necessary to take advantage of the
multi-resolution of the pyramidal map file. Otherwise the maximum
resolution is always the one lookedup by mental ray (thus more
memory).
Alan: I also suspect network issue, although as you said, such a
dramatic increase in render time is quite strange.
Bernard
On 5/31/05, Alan Jones <a class="moz-txt-link-rfc2396E" href="mailto:skyphyr
@(protected)"><skyphyr@(protected)></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Maybe with that render time a lot of it's reading the files
off the
disk? Pulling the .pic into memory then uncompressing it within memory
may be signicantly faster. Though I wouldn't expect it to make such a
huge difference.
That's the only guess that comes to mind though sorry.
Cheers,
Alan.
On 5/31/05, Brad Friedman <a class="moz-txt-link-rfc2396E" href="mailto:xsibrad
@(protected)"><xsibrad@(protected)></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">This is a question more than an answer:
Why convert to pyramid if you're going to use elliptical filtering? I
thought the two were entirely different types of filters. Or can
elliptical filtering take advantage of a pyramid texture?
-brad
Bernard Lebel wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Hi,
I am baffled at something. I have a scene with rather large textures
(3500x3500 and higher). In Pic format, it renders in 45 seconds.
So I'm looking to save render time, and memory while we're at it, so I
convert textures to pyramidal map float files (imf_copy -p [...] map
rgba_fp).
Then I turn on elliptical filtering, set the Maximum Pixels for
Minimum Radius to a low value 1.3, because higher than that is
generally not necessary.
In the past, I got much faster render times. However right now the
render time explodes: it's at least 5 times longer than with the Pic
version.
Any idea?
Thanks
Bernard
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