[yt-dev] Orientation vectors
John ZuHone
jzuhone at gmail.com
Wed Aug 22 09:50:00 PDT 2012
Hi Nathan,
Do you have a reference for the calculation of the north and east vectors?
John
On Aug 22, 2012, at 11:21 AM, Nathan Goldbaum wrote:
> Hey John,
>
> I think the issue is that yt uses a left-handed coordinate system internally. This particular choice makes it so that if you create a volume rendering, off axis slice plot, or off axis projection it is oriented in the same way as a regular slice or projection. Of course if you don't like that convention you can always specify a north_vector.
>
> If you want to transform to your sky coordinate frame you will need to come up with a more general transformation matrix rather than multiplying by x, y, and z scalars (i.e. a diagonal transformation matrix). Fortunately the orientation class already does the hard work for you, I think all you need to do is multiply the (x,y,z) vector by the orientation.unit_vectors matrix (maybe orientation.inv_matrix, sorry, this 3D geometry stuff always confuses me ;)
>
> Hope that helps.
>
> Nathan
>
> On 8/22/12 10:23 PM, John ZuHone wrote:
>> Hi all, and specifically to those of you with experience with the Orientation vectors...
>>
>> Doing some testing, I set up an orienter like this:
>>
>> orient = Orientation([0.0,0.0,1.0])
>>
>> and the output of orient.unit_vectors is:
>>
>> [array([ 0., -1., 0.]), array([ 1., 0., -0.]), array([ 0., 0., 1.])]
>>
>> which I would have expected
>>
>> [array([ 1., 0., 0.]), array([ 0., 1., 0.]), array([ 0., 0., 1.])]
>>
>> although I know I could fix this by specifying a north_vector, why would the latter not be the default?
>>
>> I'm asking because I was attempting to set up new coordinates like so:
>>
>> orient = Orientation(L)
>>
>> x_hat = orient.unit_vectors[0]
>> y_hat = orient.unit_vectors[1]
>> z_hat = orient.unit_vectors[2]
>> xsky = x*x_hat[0] + y*x_hat[1] + z*x_hat[2]
>> ysky = x*y_hat[0] + y*y_hat[1] + z*y_hat[2]
>> zsky = x*z_hat[0] + y*z_hat[1] + z*z_hat[2]
>>
>> but this will rotate the x,y plane by 90 degrees.
>>
>> Best,
>>
>> John
>> _______________________________________________
>> yt-dev mailing list
>> yt-dev at lists.spacepope.org
>> http://lists.spacepope.org/listinfo.cgi/yt-dev-spacepope.org
>
> _______________________________________________
> yt-dev mailing list
> yt-dev at lists.spacepope.org
> http://lists.spacepope.org/listinfo.cgi/yt-dev-spacepope.org
More information about the yt-dev
mailing list