Eular angle in frealign
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Hi niko,
I am trying do a Eular angle(output from frealign) comparison. Could you confirm the angle setting for me?
I always think FREALIGN takes the same Z-Y-Z rotation setting as SPIDER, that is, first rotate "phi" around Z, and then "theta" around Y, finally "psi" around Z. So, if writng in a matrix formula, it is
r1=R(psi)*R(theta)*R(phi)*r0 . (1)
But in FREALIGN, I found the formula is
r1=r0*R(psi)*R(theta)*R(phi) . (2)
Am I right? If yes, is the reason that r0 in FREALIGN is a reciprocal-space vector, but may be a real-space vector in SPIDER? But in my understanding, no matter r0 is a reciprocal-space or real-space vector, we can use the same eqution(1).
Thank you.
xueming
To further confirm, I tried
To further confirm, I tried to build a relationship between eqution(1) and (2) based on transpose(R)=inv(R).
Then I get:
spider(phi) = -frealign(psi)
spider(theta) = -frealign(theta)
spider(psi) = -frealign(phi)
It looks right by drawing some aligned 2D images in a 3D view.
I think you are right using
In reply to To further confirm, I tried by xueming
I think you are right using the negative Frealign angles. There is always an ambiguity regarding the meaning of the angles. They could mean the angles that need to be applied to align the particle, or they are the angles that were "applied" to misalign the particle. One will be the negative of the other. In Frealign, the angles give the rotations that need to be applied to bring the particle back into alignment.