Fwd: FixedZYZ fixed_zyz_from_rotation
2010/1/30 Daniel Russel drussel@gmail.com: > Check that the choice of Euler angles isn't singular near that point (each > choice of Euler angles has a place where it is singular, meaning very > different Euler angle values produce almost the same rotation).
Yes, I think that is what is happening here, but I don't know how to repair it.
How does the > instability manifest itself.
When psi is 0, then sin(psi) = 0 and you're dividing by it. Needs a check, that is what I did. Does it help?
> > I'll try to look more into it later. > > > On Jan 29, 2010, at 8:46 PM, Javier Ángel Velázquez Muriel > javi@salilab.org wrote: > >> That function enters into numerical instability when >> sin_tilt_sin_psi==0, which produces psi ==0. I've tried to fixe it, >> and i think is correct, but now the code throws the exception. The >> input and output are "apart". Can anybody help me to fix it? Anything >> that I missed? >> >> double psi= std::atan2(sin_tilt_sin_psi, cos_psi_sin_tilt); >> if(almost_equal(sin_tilt_sin_psi,0,1e-6)) { >> double sin_tilt= 0; >> double tilt= std::atan2(sin_tilt, cos_tilt); >> } else { >> double sin_tilt= sin_tilt_sin_psi/std::sin(psi); >> double tilt= std::atan2(sin_tilt, cos_tilt); >> } >> // double cos_rot= cos_rot_sin_tilt/sin_tilt; >> // double sin_rot= sin_rot_sin_tilt/sin_tilt; >> // double rot= std::atan2(sin_rot, cos_rot); >> double rot= std::atan2(sin_rot, cos_rot); >> _______________________________________________ >> IMP-dev mailing list >> IMP-dev@salilab.org >> https://salilab.org/mailman/listinfo/imp-dev > > _______________________________________________ > IMP-dev mailing list > IMP-dev@salilab.org > https://salilab.org/mailman/listinfo/imp-dev >
I see the problem, I'll figure out a better way to structure the computations.
On Jan 31, 2010, at 3:17 PM, Javier Ángel Velázquez Muriel <javi@salilab.o rg> wrote:
> 2010/1/30 Daniel Russel drussel@gmail.com: >> Check that the choice of Euler angles isn't singular near that >> point (each >> choice of Euler angles has a place where it is singular, meaning very >> different Euler angle values produce almost the same rotation). > > Yes, I think that is what is happening here, but I don't know how to > repair it. > > How does the >> instability manifest itself. > > When psi is 0, then sin(psi) = 0 and you're dividing by it. Needs a > check, that is what I did. Does it help? > >> >> I'll try to look more into it later. >> >> >> On Jan 29, 2010, at 8:46 PM, Javier Ángel Velázquez Muriel >> javi@salilab.org wrote: >> >>> That function enters into numerical instability when >>> sin_tilt_sin_psi==0, which produces psi ==0. I've tried to fixe it, >>> and i think is correct, but now the code throws the exception. The >>> input and output are "apart". Can anybody help me to fix it? >>> Anything >>> that I missed? >>> >>> double psi= std::atan2(sin_tilt_sin_psi, cos_psi_sin_tilt); >>> if(almost_equal(sin_tilt_sin_psi,0,1e-6)) { >>> double sin_tilt= 0; >>> double tilt= std::atan2(sin_tilt, cos_tilt); >>> } else { >>> double sin_tilt= sin_tilt_sin_psi/std::sin(psi); >>> double tilt= std::atan2(sin_tilt, cos_tilt); >>> } >>> // double cos_rot= cos_rot_sin_tilt/sin_tilt; >>> // double sin_rot= sin_rot_sin_tilt/sin_tilt; >>> // double rot= std::atan2(sin_rot, cos_rot); >>> double rot= std::atan2(sin_rot, cos_rot); >>> _______________________________________________ >>> IMP-dev mailing list >>> IMP-dev@salilab.org >>> https://salilab.org/mailman/listinfo/imp-dev >> >> _______________________________________________ >> IMP-dev mailing list >> IMP-dev@salilab.org >> https://salilab.org/mailman/listinfo/imp-dev >> > _______________________________________________ > IMP-dev mailing list > IMP-dev@salilab.org > https://salilab.org/mailman/listinfo/imp-dev
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