[Yt-dev] HEALpix volume rendering

[Matthew Turk]

Hi all,

Just wanted to let you know that I've put in experimental support for
volume rendering using HEALpix to define the direction of vectors, all
of which will then start at the camera location and then move radially
outwards, to give a set of rays that cover the entire sky with equal
area.  ( http://healpix.jpl.nasa.gov/ )

This is not adaptive in any way; these rays will not split along their
trajectories, which is broadly problematic.  Additionally, the bricks
are not sorted yet, so currently only projection transfer functions
(column density) are supported.  I'll add support for ordering the
grids so that more complicated things that require inputs from
previous bricks can be accomplished, but for now it's only useful for
column density and averaging operations.

Anyway, if you're interested in playing with this, I've put up a script here:

http://paste.enzotools.org/show/1498/

And I've extracted portions of the healpy module that are necessary to
plot a Molleweide projection, which can be found here:

http://yt.enzotools.org/files/mv.txt

note that once you download, you have to change mv.txt to mv.py.
Attached is an image from one of the test simulations we used at the
Enzo workshop, where I've tossed out nside=64 (12*64*64 vectors) out
to a radius of 0.1 of the box.  I then plotted the column density.
This is the output from the linked script, above.  This functionality
is also able to do angular-averages of values, which is kind of cool
(and what I am applying it to.)

My plan is to add correct ordering of grids, create a Molleweide
projection that is small and works like other yt plots, and then to
make it easier to generate and plot.  If anybody wants to help out,
I'd be appreciative -- particularly with the generation of projections
and plotting of them.

-Matt
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