[Yt-dev] VTK interface (and how this ties to the Raft)

[Matthew Turk]

Hi everyone,

As per Sam's request (offline) to get some info about how to use the
VTK interface, I'm writing an email to start a dialogue about this.
Right now, the VTK interface is exposed through the next version of
reason, which is stored inside this mercurial repository:

http://hg.enzotools.org/yt

Here are the requirements:

  * VTK
  * ETS

If you install VTK, be sure to install the Python bindings.  During
the cmake phase, you will have to ensure that the Python interpreter
pointed to is the same one you used to install yt.  You *may* have to
manually edit the CMakeCache file to ensure that it does *NOT* install
with a "--prefix" command, which will confuse the situation.  I will
speak below, briefly, about my feelings on the Raft and how it plays
into all of this.  Once you have installed VTK, you should be able to
install ETS (code.enthought.com) with

$ easy_install "ETS[nonets]"

but, if not, do a manual source install.  This will involve a couple
more steps -- getting ETSProjectTools, running "ets co ets" and then
doing "ets develop" in the ets directory.  Alternatively, the newest
EPD (5.0) is supposedly far more stable and easy to install and get
working on OSX.

Check out the hg and update to branch 'yt'.  Now execute the command:

$ python2.5 yt/reason/reason_v2.py

and you will have access to the next-gen GUI.  Open up a parameter
file and you then have access to the VTK interface by right clicking
on the parameter file in question.  This is a developing project that
I haven't really played with in a few months.  However, it can do
isosurfaces, marching cubes, cutting planes, box outlines, camera
paths (save to a file, even, and export to Amira format) and some
other stuff.  It's also stereo-enabled.  With John Wise's work on a
software-volume renderer (and any future developments on that)
hopefully this will also become a gateway for setting up renderings of
datasets after prototyping.  I know that Sam Skillman has also
expressed interest in using this as a platform for rendering.

Okay, so, that was kind of a pain, right?  Well, that's where the Raft
came in.  I began the Raft project when I saw how the FEMhub guys had
undertaken the task of getting Mayavi2 and its dependencies (Traits,
VTK, etc etc) installed in a simple, cross-platform manner.  Right
now, it already installs VTK and Traits (not on OSX, but that should
change by endofthemonth according to Ondrej Certik and Prabhu
Ramachandran) and I am working on getting wxPython to install as well,
as available.  If I can get wxPython to go, then we should be 100% set
up for running this next-gen GUI with embedded VTK.  However, an
additional and awesome feature of the Raft (that I cannot take any
credit for) is that it includes off-screen rendering, done via Mesa.
If the VTK code I've written can be refactored to have the rendering
independent of the GUI, then this will also become a viable mechanism
for rendering.  I've done this, via monkeypatching and hackery,
already with a RAFT notebook -- I made some images of a cosmology
dataset, rendered with Mesa, using VTK widgets, displayed through a
web browser.  If anyone is interested I can post that worksheet.

Sam, if you run into any problems, please feel free to reply to this
message so we can figure them out together and move forward.  I'm very
excited about all this, and I'd really like to bring more people on
board with developing the VTK interface and the GUI.  I've been in
touch with Prabhu from the MayaVi project, and he has sent me a patch
to read in MultiBlock data in MayaVi.  Currently we use the
HierarchicalBoxDataSet, which I've modified the patch to support as
well.  I'd like to continue working on that project, but I might need
some help in that department from other people -- but if we can get
our data into MayaVi, that would be a huge step forward in usability
and exploration.

-Matt