Sketch Analysis Tools¶

In one sentence: A collection of diagnostic and maintenance tools for inspecting constraint health, selecting specific categories of geometry, and bulk-deleting geometry or constraints from a sketch.

Overview¶

Workbench: Sketcher · Menu: Sketch → Sketcher analysis / Sketch
Toolbar: Sketcher Analysis / Sketch · Shortcut: various

These tools help you understand what is happening in a complex or broken sketch without manually searching through every element.

Tool	Description
Select Associated Constraints	Select all constraints connected to the currently selected geometry
Select Origin	Select the sketch origin point
Select Vertical Axis	Select the sketch Y-axis construction line
Select Horizontal Axis	Select the sketch X-axis construction line
Select Redundant Constraints	Select all constraints the solver has flagged as redundant
Select Conflicting Constraints	Select all constraints causing over-constraint conflicts
Select Malformed Constraints	Select all degenerate or broken constraints
Select Partially Redundant Constraints	Select constraints that partially overlap with others
Select Associated Geometry	Select all geometry connected to selected constraints
Select Under-Constrained Elements	Select all geometry with remaining degrees of freedom
Toggle Internal Geometry	Show/hide internal geometry of ellipses, B-Splines, etc.
Delete All Geometry	Remove every geometry element from the sketch
Delete All Constraints	Remove every constraint from the sketch
Remove Axes Alignment	Delete any horizontal/vertical constraints imposed by automatic axes alignment

Intuition¶

A complex sketch with 50+ elements and 100+ constraints can become hard to navigate visually. These selection tools act like a filter: "show me only what is broken" or "show me everything connected to this constraint." Once the relevant elements are selected, you can inspect, delete, or replace them efficiently.

The bulk-delete tools (Delete All Geometry, Delete All Constraints) are "nuclear options" for restarting a sketch or clearing imported noise without leaving the sketch edit mode.

When to use them¶

Select Redundant / Conflicting Constraints: Your sketch turned red and you cannot find which constraints are in conflict. Use these tools to highlight them, then delete the duplicates.
Select Under-Constrained Elements: You cannot close the sketch because some elements are still white. Use this tool to highlight every remaining under-constrained element and systematically constrain them.
Toggle Internal Geometry: You drew an ellipse but cannot see its focus points to add constraints to them. Toggle internal geometry to show them.
Select Associated Constraints: You want to delete a line but need to know which constraints reference it first.
Delete All Geometry / Constraints: You imported a DXF that is a mess and want to start fresh, or you want to completely repopulate the constraint set.

Step-by-step walkthrough¶

Finding and fixing redundant constraints¶

Enter sketch edit mode (double-click the sketch).
Notice elements turning red — the solver reports an over-constraint.
Sketch → Select Redundant Constraints. The redundant constraints are highlighted (selected) in the viewport.
Press Del to remove the selected redundant constraints.
The sketch returns to a valid (non-red) state.

Finding under-constrained elements¶

In sketch edit mode, the DoF counter shows a positive number (e.g. "3 DoF").
Sketch → Select Under-Constrained Elements. All white (unconstrained) geometry is now selected.
Apply the appropriate constraints to the selected elements.
Repeat until DoF = 0 and all elements are green.

Toggling internal geometry¶

Select an ellipse or B-Spline in the sketch.
Sketch → Toggle Internal Geometry (or right-click → Toggle internal geometry).
The focus points, weight circles, and control polygon appear/disappear.
With internal geometry visible, select focus points to add constraints.

Parameters¶

Most analysis tools have no parameters — they are one-click actions. Exceptions:

Delete All Geometry / Delete All Constraints: A confirmation dialog appears to prevent accidental bulk deletion.

Advanced usage¶

Remove Axes Alignment¶

When you draw a rectangle or import geometry, FreeCAD may automatically add Horizontal and Vertical constraints to enforce axis alignment. If you want to rotate the geometry afterwards, these constraints prevent it. Use Remove Axes Alignment to delete them in bulk and then apply an Angle constraint instead.

Select Associated Geometry and Constraints (workflow)¶

These two tools work together for constraint archaeology:

Select a problematic constraint → Select Associated Geometry → see which edges it references.
Select a problematic edge → Select Associated Constraints → see which constraints reference it.

Use this pair when trying to understand why a change to one element breaks something unexpected elsewhere in the sketch.

Python API¶

Select under-constrained elements (inspection)¶

import FreeCAD as App

doc = App.activeDocument()
sketch = doc.getObject("Sketch")

# Check degrees of freedom
dof = sketch.getDOF()
print(f"Remaining DoF: {dof}")

# List which constraints are redundant (solver result)
redundant = sketch.getRedundancies()
print(f"Redundant constraint indices: {redundant}")

# List conflicting constraints
conflicting = sketch.getConflicts()
print(f"Conflicting constraint indices: {conflicting}")

Delete all constraints¶

# Remove all constraints from the sketch
sketch.deleteAllConstraints()
doc.recompute()

Toggle construction mode (internal geometry)¶

import Sketcher

# Toggle a geometry element between regular and construction mode
sketch.toggleConstruction(geoIndex)
doc.recompute()