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If you can describe the galaxy using a data object (sphere, disk, etc), you could then do something like galaxy_object.quantities'BulkVelocity' to get the motion of just that piece of the data. I'm not sure if that is helpful for you or not.
I would say that it would be best to get on a more recent version of yt, where you will be able to use the tranpose, and the north vector will make more sense with option 1 or 3.
On Mon, Jan 14, 2013 at 7:25 AM, Renyue Cen email@example.com wrote:
I am using option (2) below without transpose (per your suggestion to fix the symmetric image problem) and it does seem to point to the right (I have a bit trouble to decide exactly at which direction the galaxy is traveling even though I have its peculiar velocity, because I do not have information about the velocity of the volume it is in).
On Jan 14, 2013, at 10:17 AM, Sam Skillman wrote:
It depends a bit on how you are saving the image, unfortunately. If you are using a recent changeset of yt (after 2.4 where the transpose causes symmetric images on some compilers/machines), and you save with:
cam.snapshot('image1.png') Then image1.png will have north pointing up.
If you did: im = cam.snapshot() write_bitmap(im, 'image2.png', tranpose=False) Then image2.png will have north pointing right.
If you did im = cam.snapshot() write_bitmap(im, 'image3.png', transpose=True) Then image3.png will have north pointing up.
I am working on ways to make sure that it always points up by using the new ImageArray class, but have not come up with the full solution yet. I hope that description helps.
On Sat, Jan 12, 2013 at 8:12 PM, Renyue Cen firstname.lastname@example.org:
I think I am unclear about the orientation in pf.h.camera(c,W,L, ..., north=vec, ...). I got some nice looking pictures but don't know what north means in this case, because when I switch north=vec to north=reverse of vec, the image rotates along the vertical direction, so it seems like north is pointing to either left or right. It is very desirable for me to be able to make sure which direction vec points to (vec is the vec in north=vec) in the final rendered plot.
Thanks in advance for help, Renyue