A Detailed Troubleshooting and Technical Analysis Guide
1. Introduction
Many users upgrading from FreeCAD 1.0.2 to newer versions (1.1.0 / 1.1.1) encounter a confusing issue in the Sketcher workbench:
Changing a dimension (e.g., 10 mm → 100 mm) does NOT visually update the sketch geometry.
However:
- Pad/extrusion shows correct dimensions
- Measurement tools report correct values
This leads to the false assumption that the sketch is not working correctly.
2. Problem Statement
Typical Symptoms
- Line length changed, but visually unchanged
- Rectangle dimensions modified, but shape appears same
- Sketch appears “frozen”
- After exiting Sketcher and creating Pad → correct size appears
Key Observation
Geometry is updated internally, but not refreshed visually.
3. Root Cause Analysis (Technical)
This issue originates from a GUI refresh / rendering synchronization problem, not a modeling failure.
FreeCAD architecture involves three layers:
1. Constraint Solver
- Computes geometry correctly
- Fully functional
2. Document Recompute Engine
- Updates parametric model
- Works correctly
3. View Provider (Rendering Layer)
- Responsible for drawing sketch
- Fails intermittently in v1.1.x
👉 The issue lies in Layer 3
4. Why This Happens in Version 1.1.x
FreeCAD 1.1 introduced a major redesign of External Geometry tools:
Old System (≤ 1.0.2)
- Single tool: External Geometry
- Passive reference only
- You can download the old and stable version FreeCAD 1.0.2 from Source Forge on this link.
New System (≥ 1.1.x)
- External Projection
- External Intersection
- More complex geometry mapping
This required deep internal changes in:
- Sketcher solver interactions
- Geometry update pipeline
- OpenGL rendering synchronization
👉 Result: Occasional UI refresh failures
5. Why It Is Not Always Detected
This bug is intermittent and system-dependent:
- GPU driver differences
- OpenGL implementation
- OS-level rendering
- Interaction timing
Thus:
- Works fine on some systems
- Fails on others
6. Immediate Workarounds
Method 1: Force Recompute
Press:
- Ctrl + R
OR
- Edit → Refresh/Recompute
Method 2: Exit Sketcher
- Close Sketch
- Reopen it
Method 3: Create Feature (Pad)
- Perform Pad operation
- Verify correct geometry
7. Permanent Solution (Recommended)
Use FreeCAD 1.0.2 for Stability
Advantages:
- Stable Sketcher behavior
- Reliable visual updates
- Predictable constraint solving
Trade-off:
- No External Projection / Intersection tools
8. Best Workflow Strategy
Recommended approach:
- Use FreeCAD 1.0.2 for:
- Teaching
- Classroom demonstrations
- Stable modeling work
- Use FreeCAD 1.1.x for:
- Testing new features
- Advanced projection/intersection tasks
9. Engineering Perspective
This is not a “bug due to carelessness” but a transition-phase instability:
- Version 1.0 → Stable baseline
- Version 1.1 → Feature expansion
- Future versions → Stabilization
Such behavior is common in complex parametric CAD systems.
10. Comparison with Commercial CAD
Commercial tools like:
- SolidWorks
- Fusion 360
Have:
- Dedicated QA teams
- Automated UI testing
- Hardware validation
FreeCAD (open-source):
- Community-driven
- Limited QA infrastructure
11. Final Conclusion
If you face Sketcher not updating visually in FreeCAD 1.1.x:
Your model is correct. The display is wrong.
For reliability:
- Prefer FreeCAD 1.0.2
For advanced features:
- Use 1.1.x cautiously with manual recompute
12. Practical Advice
Always verify using:
- Measurement tools
- Pad/3D features
Never rely solely on sketch appearance in unstable versions.
13. Author Note
This guide is intended to help students, educators, and engineers avoid confusion and save time while working with FreeCAD.
