Hi, In an attempt to find the problem causing this bug, I dug into the code and found something which could be erroneous... This alone does not fix the bug, but may be part of the fix (or not)... In function math_fns/direction_cosine.calc_ellipsoid_di(), there could be an error at line 229: diff_data.dz[1] = data.sin_b * data.sin_g If I am right (?), this part of the code is related to page 193 of Edward d'Auvergne's thesis: c11 = diff_data.dx[0] c21 = diff_data.dx[1] c31 = diff_data.dx[2] c12 = diff_data.dy[0] c22 = diff_data.dy[1] c32 = diff_data.dy[2] c13 = diff_data.dz[0] c23 = diff_data.dz[1] --> FALSE !!!! c33 = diff_data.dz[2] Indeed, c23 = sin(beta) * cos(gamma), whereas diff_data.dz[1] = data.sin_b * data.sin_g Thus, either me, the code or Edward's thesis are erroneous here... Am I right ? Regards, Séb :) Sébastien Morin wrote:
Hi, We (Pierre-Yves Savard and I) have found a problem with the structure.create_diff_tensor_pdb() function. If you use either results.read() or diffusion_tensor.init() to load a diffusion tensor and, then, display it, it is fine, except for the ellipsoid where some weird things happen... Indeed, with the ellipsoid, you get a weird shaped tensor, depending on the angles input. With angles set to 0, the tensor is fine. With alpha and beta set to non-zero values, the shape of the tensor changes drastically as it becomes completely flat. With gamma set to a non-zero value, the shape is fine, with the tensor just turned around the Dz axis... I submitted a bug report and attached 7 files: tensor.pdb With all angles set to 0. tensor__angles__alpha_90.pdb With alpha = 90 degrees. tensor__angles__beta_90.pdb With beta = 90 degrees. tensor__angles__gamma_90.pdb With gamma = 90 degrees. tensor__angles__all_90.pdb With all angles set to 90 degrees. tensor__angles__all_45.pdb With all angles set to 45 degrees. tensor__angles__45_0_45.pdb With all angles set to 45, 0 and 45 (alpha, beta and gamma, respectively). As you will see, the tensor is fine if both alpha and beta are equal (files: tensor__angles__all_45.pdb and tensor__angles__all_90.pdb), but weird shaped when alpha and beta are not equal (tensor__angles__45_0_45.pdb)... These observations were made with the subversion repository. I verified with relax-1.3.1 / relax-1.3.2 / relax-1.3.3 and the same problem arises... so the problem as been there for a long time... Shouldn't the tensor always keep a symmetric shape, with angles only changing the orientation, not the shape..? Thanks for help. Séb :) -- Sébastien Morin PhD Student S. Gagné NMR Laboratory Université Laval & PROTEO Québec, Canada _______________________________________________ relax (http://nmr-relax.com) This is the relax-users mailing list relax-users@xxxxxxx To unsubscribe from this list, get a password reminder, or change your subscription options, visit the list information page at https://mail.gna.org/listinfo/relax-users
-- Sébastien Morin PhD Student S. Gagné NMR Laboratory Université Laval & PROTEO Québec, Canada