[yt-users] volume rendering brightness

[Geoffrey So]

Thanks Britton and Sam,

I've went through the videos on volume rendering and tried what Cameron
showed with clip_ratio, it lessened the changing brightness from angle to
angle somewhat, but it's Sam's enhance.py that does the trick, at least to
my eyes.

I would highly recommend sticking the links of these videos on the
documentation or example page.  I know they say a picture is worth a
thousand words, so videos such as these are worth say 30 frames per second
* length of videos = ...

Loved the videos

From
G.S.

On Tue, Feb 28, 2012 at 6:39 AM, Sam Skillman <samskillman at gmail.com> wrote:

> Hi Geoffrey,
>
> Another option, which is outlined in the Advanced Rendering talk from the
> workshop, is to use an enhance script to renormalize the image.  This
> doesn't require setting the clip variable, and is done as a post-processing
> step.  The video of the talk, as well as slides, can be found here (see
> Advanced Rendering):
> http://yt-project.org/workshop2012/#presentations
>
> It references an enhance.py script, which can be found through the hub,
> here:
> http://hub.yt-project.org/AnalysisAndVisualization/enhance-your-renderings/
>
> I'd suggest taking a look, as it will also walk you through other advanced
> rendering techniques.
>
> Best,
> Sam
>
>
> On Tue, Feb 28, 2012 at 5:50 AM, Britton Smith <brittonsmith at gmail.com>wrote:
>
>> Hi Geoffrey,
>>
>> The brightness of the total image is basically normalized to the
>> brightest pixel.  Occasionally, when you rotate the domain, a single pixel
>> will be incredibly bright which will cause the rest of the image to be dim
>> by comparison.  You can fix this in with the snapshot call by adding the
>> keyword,  clip_ratio=some_float.  This limits the maximum brightness to no
>> more than a fixed number of standard deviations from the mean.  I recommend
>> you start with a clip ratio of 5 or 6 and play around with it.
>>
>> Briton
>>
>> On Mon, Feb 27, 2012 at 7:57 PM, Geoffrey So <gsiisg at gmail.com> wrote:
>>
>>> Hi volume rendering experts,
>>>
>>> I was playing around with a density volume render of a tiny cube on my
>>> laptop, everything went smoothly, however, I notice a change in "overall"
>>> brightness between images when I did a rotation.  I'm not sure how to
>>> explain this, but it seems that from images of different angles, sometimes
>>> the average brightness is consistent, but sometimes it suddenly drops and
>>> the image would look about half as bright, and after a couple frames it
>>> would light back up.
>>>
>>> I'm guessing this is after each image is ray casted, it gets normalized
>>> to a certain value, and that value changes depending on the angle?  Is
>>> there a way to pin the brightness between images so if I make a movie it
>>> won't dim and light up as I rotate?
>>>
>>> Also I was wondering if I'm the only person to notice this? (the only
>>> other post I found about volume render brightness is about AMR cell
>>> contributions)
>>>
>>> From
>>> G.S.
>>>
>>> _______________________________________________
>>> yt-users mailing list
>>> yt-users at lists.spacepope.org
>>> http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org
>>>
>>>
>>
>> _______________________________________________
>> yt-users mailing list
>> yt-users at lists.spacepope.org
>> http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org
>>
>>
>
> _______________________________________________
> yt-users mailing list
> yt-users at lists.spacepope.org
> http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.spacepope.org/pipermail/yt-users-spacepope.org/attachments/20120228/180921a7/attachment.html>