Digital Universe: Locating the Great Coma Wall

[Rusty Williamson]

Hi,

I'm not sure at all if this is the proper forum for my question but I'm getting desperate. I've been learning how to use the Digital Universe and partview but my main objective is locating the Great Coma Wall and 'flying' from it to the Milky Way. This is research for a science fiction book. If anyone can help in any way (how to locate it, a better forum or source to post this query, etc.) I'd be very thankful.

Rusty

[Stuart Levy]

Hello Rusty,

Are you hoping to record an animation of a flight from the Milky Way to the Great Wall, that makes it look like a wall? Or just to fly around the neighborhood to get your own impression of what's there?

Some big galaxy clusters that are part of the Great Wall, and their coordinates in the supergalactic system which that galaxy dataset is using:

0.52 69.11 10.16 Abell 1656 (Coma cluster)
-2.39 62.85 -11.71 Abell 1367 (in Leo)
18.08 57.06 71.83 Abell 2199 (in Hercules)

That should give a general idea of where the Great Wall lies. There are lots of galaxy clusters, and filaments between them, out there - roughly spanning a fair part of the +Y face of the data box in that dataset.

Does that help?

[Rusty Williamson]

Stuart,

In my sci-fi series a planet in a galaxy at the edge of the Coma Wall finds a way to chase an all-knowing alien between galactic clusters for about 200 million years at .99999 lgt speed in the general direction of the Milky Way. I want to pick a point at the edge of the 'wall' (where their galaxy is) and head towards the Milky Way for about 190 million lgt yrs and see what I encounter and use this for the basis of the story.

I went through the tutorials in the manual but I am still not sure if...
1. I can pick a location and get back to it?
2. How to use the coordinates you provided.
3. If I can plot a course and somehow save it and repeat it?
4. Can I make an animation of the a plotted course and replay it?
5. Can I somehow see a cross section slice of a (saved) path? What would be ideal would be to plot some path then capture a section surrounding that path...say a tube 20 million light years wide following the path...so I can see what I'm passing through.
6. Can I tweak the VU so I see what a person would see with the naked eye traveling this path?

Can you answer any of the above questions, LOL? I don't recall seeing any of these things in the tuts I went through. If you know something is possible I can then search around and hopefully find out how to accomplish it. I've worked with 3D animation programs for 20 years but the VU is different.

I know the coma wall was discovered in the CfA redshift survey and I've discovered that Mass2 (or something like that) contains that and how to execute a command to see only the CfA redshift survey (don't have the manual with me so my terminology is approximate).

I did not see in the tuts anyway to get to a specific location nor face a specific direction nor to know what speed you are traveling or how far...can you give me a hint?

I know...there's a lot I don't know. I have another pdf to work through.

Rusty

[Stuart Levy]

Hmm.   Doing this sort of thing - recording a path, anyway - involves external scripting of some sort.   It's not built-in to partiview.

Things you can do with it as it stands:

   (type in the text box)
       jump   X  Y  Z  [xrot yrot zrot]
   e.g. you could say
       jump 0.52 69.11 10.16
   to jump to the middle of the Coma cluster, facing whichever direction you were before

Another very useful thing is to set the "center" to be in the midst of something interesting - then you can easily tour around that point, interactively, using the left and right mouse buttons (or, left- and alt-left if you're on a Mac).  So, you could pick a point that's roughly in the middle of the three clusters I mentioned, like
    center 5 64 24
and spin around there to pick a nice starting point.

To find out where you are, just type:
    jump
and note the six numbers it prints out.   You can feed those same numbers back to a later "jump" command to return there.

You can write (probably with some sort of program) a text file where each line is some set of seven blank-separated numbers.   The first six are a set of X Y Z xrot yrot zrot, as from "jump", and the seventh is a field-of-view measure in degrees.   Then you can load that path into partiview using the "Path..." button, or the "rdata" command.   Then pressing Play will make the viewpoint tour along the given sequence of camera positions, frame by frame.

What sort of computing environment do you have?   E.g. a Mac, or a windows PC, or what?   If you have something where you can run scripts written in either the languages Perl or Python, I could send a script that would generate a path, as a command-line sort of thing.

You'd open a Terminal window (if on a Mac) or a Run -> "cmd" command window (if on Windows) and type something like:

    perl somescript.pl   startX,Y,Z   endX,Y,Z  nframes  >   pathfile.wf

and then in partiview you'd type

    rdata pathfile.wf

and hit the Play button, and it would tour along the constructed path.

There is a way to record a sequence of images too.    The "msnapper" script in the "scripts" directory (do you have that in your distribution?  if not I can send it) makes a sequence of commands that tells partiview to take a screen snapshot for every frame.  

If you're on a Mac, it should work handily.   If on Windows, it's a bit more roundabout.   I'll say more when I understand what you have to work with.   But generally you'd type something like, in the partiview text box,

     async perl msnapper    imagename.%04d.jpeg  1 nframes


You asked about making it look as it would in life - there isn't a provision for doing that.

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