Sketcher Dialog

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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:

Solver messages

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:

Name Description
Default solver The solver that is used for solving the geometry. LevenbergMarquardt and DogLeg are trust region optimization algorithms. The BFGS solver uses the Broyden–Fletcher–Goldfarb–Shanno algorithm.
DogLeg Gauss step This setting is only available for the solver DogLeg. It is the step type used in the DogLeg algorithm.
Maximum iterations If the solver needs more iterations to find a convergence to a solution, it will stop and output that it failed.
Sketch size multiplier If checked, the maximum iterations will be multiplied by the number of parameters. The idea is that bigger sketches would need more iterations to converge.
Convergence The threshold for the squared error. This error is used to determine whether a solution converges or not.
Eps/Eps1/Tau These settings are only available for the solver LevenbergMarquardt. You should only change there something if you fully understand how the LevenbergMarquardt solver works.
Tolg/Tolx/Tolf These settings are only available for the solver DogLeg. You should only change there something if you fully understand how the DogLeg solver works.
QR Algorithm During diagnosing the rank of the matrix is calculated which enables to further analyze the constraint system to determine if there are redundant/conflicting constraints. The rank revealing decomposition used in FreeCAD is QR. There are two algorithms: Eigen Dense QR is 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. The Eigen Sparse QR algorithm is an optimization for sparse matrices (having lots of zeros), which is usually much faster, since FreeCAD's systems do have a lot of zeros.
Pivot threshold When doing a QR, a value under the pivot threshold is treated as if it is zero.
Redundant Solver The solver that is used during diagnosing to determine whether a group is redundant or conflicting.
Red. Max Iterations The same as Maximum iterations, but for the redundant solving.
Red. Sketch size multiplier The same as Sketch size multiplier, but for the redundant solving.
Red. Convergence The same as Convergence, but for the redundant solving.
R.Eps/R.Eps1/R.Tau The same as Eps/Eps1/Tau, but for the redundant solving.
R.Tolg/R.Tolx/R.Tolf The same as Tolg/Tolx/Tolf, but for the redundant solving.
Console Debug mode Setting to specify the verbosity of the console output.
Solve With this button the solver will explicitly started.
Restore Defaults With this button the default solver settings will be restored.

Note: Most of the solver parameters are of no practical use. They can however help testing and understanding the solvers.

Edit controls

The edit controls are intended to improve the workflow. They can also globally set for all sketches via the sketcher preferences.

You can set the following controls:

Name Description
Show Grid If checked, a grid will be shown in the sketches.
Grid size The distance between 2 subsequent grid lines. Note that the default value of 0 mm will result in a 10 mm grid.
Grid snap If checked, new points will snap to the nearest grid crossing point. Note that the points have already to be close to a grid crossing point that the snap takes effect.

Please note that this is just a visual aid; grid snap is no substitution for coincidence constraints.

Auto constraints If checked, the sketcher proposes automatically sensible constraints. If you draw for example a polyline and point towards the bottom, you will see that the sketcher proposes a vertical constraint:. If you set now a point the drawn line segment will get the vertical constraint.
Avoid redundant auto constraints If checked, the sketcher tries not to propose redundant auto constraints. This option only has an effect if also the option Auto constraints is used.
Rendering oder The order how sketches are rendered. To change it, drag and drop one of the geometries to the top or bottom.

Constraints

Elements