[yt-users] Strange artifacts in volume rendering movie made using parallel_objects

[Stella Offner]

Hi Nathan,

I've seen the exact same behavior making yt volume renderings not  
using any parallelization, so I'm surprised if that's the problem. I  
think I've fixed it  in the past by setting the max value  
appropriately (which it sounds like you've discovered).

Stella

On Mar 1, 2012, at 4:20 AM, Nathan Goldbaum wrote:

> Hi all,
>
> This has something to do with the way the layer closest to the high- 
> density edge of the transfer function gets treated.  Setting the  
> maximum density of the transfer function to be well above the  
> maximum density in the last frame seems to be a quick fix for the  
> problem (e.g. in this new video [made with this updated script]  
> which looks pretty good until the very end).  I'm not familiar with  
> parallelism in the camera object so any advice I could get on this  
> would be greatly appreciated.
>
> I should be available on IRC tomorrow to try to work this out.
>
> -Nathan
>
> On Feb 29, 2012, at 11:04 PM, Nathan Goldbaum wrote:
>
>> Hi Sam,
>>
>> It looks like cam.comm.rank = 0 and cam.comm.size = 1 for all of  
>> the MPI tasks and at each iteration of the loop.
>>
>> Nathan Goldbaum
>> Graduate Student
>> Astronomy & Astrophysics, UCSC
>> goldbaum at ucolick.org
>> http://www.ucolick.org/~goldbaum
>>
>> On Feb 29, 2012, at 10:22 PM, Sam Skillman wrote:
>>
>>> Hi Nathan,
>>>
>>> This is pretty weird -- Can you print out cam.comm.rank and  
>>> cam.comm.size just after you create the camera object?  The only  
>>> thing I can think of is that there is some invalid reference to  
>>> the wrong communicator.  When doing this you can get rid of the  
>>> cam.snapshot so that it runs through the code much faster.  I'll  
>>> be on IRC tomorrow morning as well if you want to catch me there.
>>>
>>> Sam
>>>
>>> On Wed, Feb 29, 2012 at 8:37 PM, Nathan Goldbaum <goldbaum at ucolick.org 
>>> > wrote:
>>> Hi all,
>>>
>>> I'm running into some weird issues when I try to make a time  
>>> series volume rendering movie using parallel_objects.
>>>
>>> The script I'm running is pasted here: http://paste.yt-project.org/show/2206/
>>>
>>> And the resulting movie is located here: http://ucolick.org/~goldbaum/files/volume.avi
>>>
>>> The movie is stitched together using ffmpeg but i've confirmed  
>>> that the artifacts are present in the individual frames.  This is  
>>> not due to my use of the enhance script since the artifacts appear  
>>> in the raw frames and in fact the movie was stitched together  
>>> using the raw frames.  I don't see any artifacts when I volume  
>>> render individual frames in serial.  I'm doing one processor per  
>>> file parallelism.
>>>
>>> Thanks for your help with this - I know there's a cool looking  
>>> movie buried in there somewhere.
>>>
>>> Nathan Goldbaum
>>> Graduate Student
>>> Astronomy & Astrophysics, UCSC
>>> goldbaum at ucolick.org
>>> http://www.ucolick.org/~goldbaum
>>>
>>>
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--------------------------------------------------------------
Stella Offner
NSF Postdoctoral Fellow
Harvard-Smithsonian Center for Astrophysics
http://www.cfa.harvard.edu/~soffner





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