Multilevel refinement

Dynamo computes the angles that produce the maximum correlation in a multilevel fashion. The project parameters cone_range, cone_sampling, inplane_range and inplane_sampling determine a base level that is scanned exhaustively.

= Base level scan

During the scanning procedure, Dynamo will start with a loop on the base level angles. In this loop scans a single angle by computing the full cross correlation matrix between the rotated template and the particle. Then, a shift limiting is applied onto the matrix, and the maximal cc inside the limited ccmatrix is computed. If this maximum is larger than the previously stored maximum for the full set of angles, this angle and the shifts where the cc maximum is located are set as best aligning parameter, and the cc is stored.

The set of angles scanned at this level is regularly distributed (in the space of rotations SO(3)) around the rotation stored for the particle in the previous iteration (which should be stored in the table)

Refinement scan

When all the angles in the base level have been scanned, the optimal angles are considered and a new set of angles to scan is defined around these. The geometry of the new set is defined by the angular parameters of the previous level with this formula.

cone_range[l] = refinementFactor*cone_sampling[i-1];

cone_sampling[i] = cone_sampling[i-1]/2;

Visualizing angular distributions

You can simulate the method of Dynamo to compute a multilevel refinement with the command dynamo_angles_multigrid g=dynamo_angles_multigrid(60,3,45,5,[0,0,0],3,2,0,0);

Additional angular parameters

Some other parameters are available