Sketcher Dialog

Introduction
If you are in a sketch, the sketcher dialog is shown in the Combo view panel in the tab Tasks (task bar). To jump into a sketch, select it in the model tree an either double-click on it or right-click on it and then select Edit sketch in the context menu. Another possibility is to click on the toolbar icon (Edit sketch).

The dialog consists of the following sections:

Advanced solver control
This dialog section will only appear if you set the option Show Advanced Solver Control in the Task bar in the sketcher preferences.

You can specify the following:

Default solver: The solver that is used for solving the geometry. DogLeg Gauss step: Step type used in the DogLeg algorithm. Maximum iterations: When finding convergence do not go over this number of iterations, just fail. Sketch size multiplier: multiplies the maximum iterations by the number of parameters under the idea that bigger sketches would need more iterations to converge. Convergence: This is the threshold for the squared error used in the code to determine whether it converged or not. Tolg/Tolx/Tolf and other parameters for the other solvers: solver parameters that only somebody that fully understands what DogLeg, LM, ... do should there to touch. QR Algorithm: During diagnose the rank of the matrix is calculated which enables to further analyse the constraint system to determine if there are redundant/conflicting constraints. The rank revealing decomposition used in FreeCAD is QR. There are two algorithms, a dense matrix QR with full pivoting, which is the legacy proven algorithm that works very well but it is rather slow as the system grows, and the Sparse QR algorithm, that is an optimisation for sparse matrices (having lots of zeros), which is much faster, as our systems do have a lot of zeros. Pivot threshold: When doing QR, a value under this threshold is treated as if it where zero (affecting whether rows/columns are linearly independent or dependent) Redundant solver: A solving that is used during diagnosis to determine whether a conflicting group is redundant or conflicting. Red max iterations, the same as above but this redundant solving. Red sketch multiplier, the same as above but for this redundant solving. Red convergence and parameters, yup you guessed, the same. Console Debug mode: verbosity of the console output.

Most of these parameters are of practically no use anymore. It helped testing and understanding the solver and from time to time is may be handy to check some cases, but mostly today the solve button and the debug mode is the only thing practical from time to time.