[yt-users] Problem in simple volume rendering (yt-users Digest, Vol 36, Issue 18)

[Matthew Turk]

Hi Kuo-Chuan,

Thanks for the note, and I'm glad it is much faster now.  Sam
Skillman, who implemented the no_ghost option (over my objection,
which I freely confess was a mistake) has gone ahead and turned it on
by default, but added a warning about it.  If you end up with
artifacts, turning on no_ghost should fix them.  I also think the
performance hit is worse for FLASH than for Enzo, so we don't see it
quite as often.

I've fixed the documentation as well, but not rebuilt/reuploaded the
new docs yet.

-Matt

On Thu, Feb 24, 2011 at 6:05 PM, Kuo-Chuan Pan <kpan2 at astro.illinois.edu> wrote:
> Dear Matt,
> Thanks very much for your suggestion.
> Using the camera interface with no_ghost=True improve the calculation time
> to <5min for N=512!
> (9 level AMR with each block contains 8^3 zones)
> I found for my case, I followed the cooked
> http://yt.enzotools.org/doc/visualizing/volume_rendering.html#volume-rendering
> there is a line:
>
> cam = vr.Camera(c, L, W, (N,N), tf)
>
> but I have to put pf in the Camera class, otherwise it will not work.
>
> cam = Camera(c, L, W, (N,N), tf, pf=pf, no_ghost=True)
>
> Not sure, that is a typo in the cookbook or not.
>
> Sincerely yours,
> Kuo-Chuan
>
> ==================================
> Kuo-Chuan Pan
> Graduate Student
> Department of Astronomy
> University of Illinois at Urbana-Champaign
> Email:
> astroodie[at]gmail.com
> kpan2[at]astro.uiuc.edu
> On Feb 24, 2011, at 4:10 PM, Matthew Turk wrote:
>
> Hi Kuo-Chuan,
>
> We have seen really long calculation times in the past.  If you use
> the camera interface and specify:
>
> no_ghost=True
>
> when calling .camera( ... ) it should speed up the rendering time
> considerably.  Try the camera interface, and give a shot at the
> no_ghost option, and see if that improves it?
>
> -Matt
>
> On Thu, Feb 24, 2011 at 5:05 PM, Kuo-Chuan Pan <kpan2 at astro.illinois.edu>
> wrote:
>
> Dear Matt,
>
> Thank you so much for your help!
>
> Changing the width to pf.domain_right_edge -pf.domain_left_edge seems works
> now!
>
> but it is still calculating  (> 2hrs).
>
> I thought width=1 refer to the whole domain.
>
> After the calculation finished, I will let you know whether it works or not.
>
> Thank you so much.
>
> Best,
>
> Kuo-Chuan
>
>
>
> On Feb 24, 2011, at 3:46 PM, Matthew Turk wrote:
>
> Hi Kuo-Chuan,
>
> You can also get the full domain by using the unit 'unitary' in the
>
> same way you would use other units.  For example,
>
> 1.0/pf['unitary']
>
> should get you the largest box side length, so it should be the whole
> domain.
>
> When I update the recipes and documentation next, I will be more clear
>
> that "1.0" refers to a particular method of describing the domain, and
>
> I will move it to using "unitary" everywhere instead of the implicit
>
> domain size.
>
> Let us know how it goes!
>
> Best,
>
> Matt
>
> On Thu, Feb 24, 2011 at 2:33 PM, j s oishi <jsoishi at gmail.com> wrote:
>
> Hi Kuo-Chuan,
>
>
> 3.  I set the width = 1 as used in the example code.
>
> I think this is your problem. Flash uses cgs units, and so you are
>
> trying to volume render a volume of width 1 cm. This is far tinier
>
> than a single cell, and so no data (NoneType) is returned to the
>
> render.
>
> Instead, try setting width = pf.domain_right_edge -
>
> pf.domain_left_edge, assuming your parameter file is called pf. This
>
> should set the width to be the whole domain.
>
> I hope this helps,
>
> Jeff
>
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