To go back and forth from the SPARX (``psi_S,theta_S, phi_S ``)convention and what Chimera records( ``psi_C, theta_C, phi_C`` ):

``psi_S = pi/2 - psi_C````theta_S = theta_C````phi_S = (3*pi)/2 - phi_C``- In more detail about the relation derivation, please check the following notes ( Solution From Summer 2005):
- I created a 3 dimensional tripod with legs with three different lengths.

1. I took the tripod, saved to BRIX, and loaded into Chimera

2. Noting the original positions of the tripods legs,

- I could perform rotations around what were the original definition of the axes.

3. For each of these rotations, a, I noted the transformation recorded in Chimera as b.

- In practice, I used three rotations (positive 90 degrees about each of the original coordinate axes).

4.

- I supposed
a =

``R_alpha``b``R_beta``

for each of the rotations, a, with ``R_alpha`` and ``R_beta`` unknown but fixed.

The general solution to these sort of problems is not so easy.

But in this particular case, the problem is not quite so hard and I found (with a certain amount of guesswork):

``R_beta = R_alpha = 0 1 0, 1 0 0 , 0 0 -1 ``

Notice that ``R_beta``is its own inverse ``R_beta = R_beta^(-1)`` . So a = ``R_beta`` b ``R_beta`` and b = ``R_beta`` a ``R_beta``

- Summer 2005