[yt-users] libpng and new volume rendering methods

[Matthew Turk]

Hi everyone,

(if you're on yt-1.6, feel free to ignore this message!)

I've backported the multivariate volume rendering (for instance:
http://yt.enzotools.org/attachment/wiki/Screenshots/hiiregion_rgb.png
http://yt.enzotools.org/attachment/wiki/Screenshots/Reion512_600px.png
http://yt.enzotools.org/attachment/wiki/Screenshots/SimB-BH.png )

to the yt trunk; this also comes with the ability to project through a
simulation along a non-orthogonal vector, so you can create images
that, for instance, peer down the L vector of a gas cloud but include
contributions from all the intervening gas -- it's much faster and
higher quality than stacking cutting planes, which was the old method
for doing this.  (Example:
http://yt.enzotools.org/attachment/wiki/Screenshots/halo_0029.png )

The new backend for volume rendering should be API compatible with the
old, but if you update your installation you will have to rebuild the
C extensions either by doing:

$ yt instinfo -u

or by re-installing.  The new multivariate volume rendering as well as
the off-axis projecting have not yet been documented.

This also comes with a direct PNG writer, which is much faster than
using matplotlib for outputting raw images; it also comes with a
couple colormaps.  This requires that libpng be installed.  yt will do
its best to locate libpng, but if it cannot find it, you will have to
supply it in png.cfg, much like for hdf5 -- however, the installation
script has been updating to install libpng if requested, so if you run
into any problems, rerun a new version of the installation script.
(Running it over top of an old installation should be fine, as it will
just conduct the necessary upgrades.)

For the next release, both the new volume rendering mechanism and the
image writer will be documented in detail; the release is probably
about a week or two away.  Let me know if you're eager to get your
hands on the API docs for either of these things and I'll shoot you
some sample scripts.  If you run into any problems, let us know!

Best,

Matt