[yt-users] Rotations in off_axis_projection

James Guillochon jguillochon at cfa.harvard.edu
Thu Jan 9 10:07:00 PST 2014


Hi everyone,

I have a 3D simulation FLASH that I wish to rotate and then project using
YT. I know the transformation matrix needed to rotate the domain such that
the projection is correct, depicted in this image:
http://i.imgur.com/AOmY6Ao.png. In the image, the dashed lines are the
original coordinate system, where the original "north_vector" is the red
dashed line, and the original "normal_vector" is a green dashed line that
points out of the plane (not visible). The rotated coordinates are shown by
the solid lines. The transformation matrix A is:

A =
0.0478113 -0.345249 0.937292
0.912293 -0.367011 -0.181724
-0.406737 -0.863774 -0.297421

My question is what should I set "normal_vector" and "north_vector" to to
get the proper projection. I tried just doing A.normal and A.north, but the
projection I get is not correct. I've also tried multiplying by A_inverse,
or just multiplying normal and/or north by A (or A_inverse), and setting
the other vector to a trivial direction (such as [0,0,1]), but none of
these projections seem to be correct.

Another thing I have tried is opening the data in Visit and rotating the
domain manually, taking note of what Visit calls the "view normal" and the
"up vector". The "up vector" matches the "north vector" I calculate using
A.north, but the "view normal" does not match A.normal.

Does anyone know the proper way to go about this? Thanks!
- James

-- 
James Guillochon
Einstein Fellow at the Harvard-Smithsonian CfA
jguillochon at cfa.harvard.edu
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