[yt-dev] Issue #1133: [experimental] Alpha seems to not normalized correctly for volume sources (yt_analysis/yt)

[Suoqing Ji]

New issue 1133: [experimental] Alpha seems to not normalized correctly for volume sources
https://bitbucket.org/yt_analysis/yt/issues/1133/experimental-alpha-seems-to-not-normalized

Suoqing Ji:

This issue can be revealed by the script [here](http://paste.yt-project.org/show/5990/).

To change the length of the rays, one line could be added manually after [this](https://bitbucket.org/yt_analysis/yt/src/4148cdf287775b38e7ad9807459680cb1370daf1/yt/visualization/volume_rendering/lens.py?at=yt&fileviewer=file-view-default#lens.py-183) line:

``vectors *= 10.``

or other factor. Different images will generated. Also if we print out ``image[: , :, 3].max()`` [here](https://bitbucket.org/yt_analysis/yt/src/4148cdf287775b38e7ad9807459680cb1370daf1/yt/visualization/volume_rendering/render_source.py?at=yt&fileviewer=file-view-default#render_source.py-270), the alpha value goes anti-proportional to the length of rays.