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).
- 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