[yt-users] does anyone use volume_rendering's PerspectiveCamera?

Stuart Levy salevy at illinois.edu
Fri Dec 5 15:01:49 PST 2014


Wow, this is wonderful!   I was thinking to just rewrite it, which 
seemed easier than trying to understand the existing code, but you've 
done it so quickly - thank you!

I haven't had a chance to try your new PerspectiveCamera yet but will 
do.   It looks like a perfectly sensible computer-graphics camera, with 
field-of-view equal to 2*atan(0.5*width[0]/width[2]) and 
2*atan(0.5*width[1]/width[2]).

thanks again

     Stuart

On 12/5/14 1:07 AM, Suoqing JI wrote:
> Hi Stuart,
>
> I've just read over the source code of PerspectiveCamera, but do not 
> quite understand it... So I wrote anther version of PerspectiveCamera 
> class and pasted it here: http://paste.yt-project.org/show/5243/ 
> <http://paste.yt-project.org/show/WPJ9EYMeYDyb4oPtgC0z/>
>
> And here're the test figures of moving camera through the volume:
>
> http://pbrd.co/1FWWiLE
> http://pbrd.co/1FWWpH2
> http://pbrd.co/1FWWGJT
>
> Also, in the YT-3 dev version there're SphericalCamera and 
> StereoSphericalCamera, which will generate 360 degree dome views.
>
> PS. I'm not sure whether there'll be someone who can fix 
> PerspectiveCamera, or I'll create a PR...
>
> Best wishes,
>
> --
> Suoqing JI
> Ph.D Student
> Department of Physics
> University of California, Santa Barbara
> CA 93106, USA
>
>> On Dec 4, 2014, at 1:08 PM, Nathan Goldbaum <nathan12343 at gmail.com 
>> <mailto:nathan12343 at gmail.com>> wrote:
>>
>> Hi Stuart,
>>
>> Looking at the PerspectiveCamera source with "hg blame", it looks 
>> like it has seen only superficial changes since January 2013.  I bet 
>> what you're seeing is due to something else changing in the volume 
>> rendering interface underneath it.
>>
>> FWIW, the PerspectiveCamera does have tests:
>>
>> https://bitbucket.org/yt_analysis/yt/src/5cd6764df8f3fbb981eefa5f19ee9f98b0ed61f6/yt/visualization/volume_rendering/tests/test_vr_cameras.py?at=yt#cl-91
>>
>> But the tests only check to make sure the camera works without 
>> crashing, and does not verify that the answer is correct.  It's 
>> entirely possible something has broken in the last two years.
>>
>> -Nathan
>>
>> On Thu Dec 04 2014 at 1:01:51 PM Michael Zingale 
>> <michael.zingale at stonybrook.edu 
>> <mailto:michael.zingale at stonybrook.edu>> wrote:
>>
>>     Hi Stuart, I've had a similar experience and haven't looked back
>>     at it in about 6 mos.  I was planning on waiting until the new
>>     renderer is in, and then I was going to try again.
>>
>>     Mike
>>
>>     On Thu, Dec 4, 2014 at 2:55 PM, Stuart Levy <salevy at illinois.edu
>>     <mailto:salevy at illinois.edu>> wrote:
>>
>>         I know it's being rewritten, thanks to Sam and Cameron and
>>         others, but I'm hoping to use some sort of perspective camera
>>         for volume rendering.   (What I'll eventually want is the
>>         dome camera which I know also exists, but wanted to start
>>         with a simpler plane-projection perspective camera.)
>>
>>         What I get: plausible images from the default orthographic
>>         Camera, but reliably blank images from PerspectiveCamera.
>>
>>         If I extract the sampler rays from PerspectiveCamera and plot
>>         them, they always seem to point in the hemisphere away from
>>         the given center point.   If I change the sign of Z width,
>>         the viewpoint is put on the opposite side of the data region,
>>         and the rays still point away from it.
>>         Also they're extremely short, like .001 or so of the distance
>>         from the viewpoint to the center point - much too short to
>>         intersect anything if the viewpoint is outside of the data
>>         volume.
>>
>>         If I hack the sampler vectors in PerspectiveCamera to (a)
>>         reverse their direction and (b) make them many times longer,
>>         I do see something.
>>
>>         I don't know whether I'm passing nonsense parameters to
>>         PerspectiveCamera, or whether its current code is really not
>>         right...?
>>
>>         A sample program, which contains its own replacement for
>>         Camera.snapshot() that allows for tweaking PerspectiveCamera
>>         rays, is in:
>>
>>         http://paste.yt-project.org/show/5240/
>>
>>
>>
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>>
>>
>>
>>     -- 
>>     Michael Zingale
>>     Associate Professor
>>
>>     Dept. of Physics & Astronomy . Stony Brook University . Stony
>>     Brook, NY 11794-3800
>>     /phone/:  631-632-8225
>>     /e-mail/: Michael.Zingale at stonybrook.edu
>>     <mailto:Michael.Zingale at stonybrook.edu>
>>     /web/: http://www.astro.sunysb.edu/mzingale
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