feat: Add Python-based chamfered View Cube for 3D CAD navigation

[PredictiveManish]

Task-1: Develop a Python-based view cube for Osdag.

Summary

Replaced the crash-prone C++ AIS_ViewCube with a pure Python implementation using PySide6 and OpenCascade geometry. This resolves stability issues, especially on Linux machines.

Changes Made

New file: view_cube.py

• Created ChamferedViewCube class using OCC's BRepFillet_MakeChamfer
• Supports 26 interactive regions (6 faces, 8 corners, 12 edges)
• Provides smooth view transitions to standard orientations

New file: view_cube_widget.py

• PySide6-based overlay widget for rendering the view cube
• Interactive drag-to-rotate functionality
• Click-to-set-view with visual feedback
• Highlighted faces based on current view orientation

Modified: custom_3dviewer.py

• Integrated Python View Cube widget as primary navigation
• Added signal/slot connection for view change events
• Smooth 3D camera rotation on view selection

Key Features

• Chamfered edges: Beveled cube edges for better clickability
• Rotatable: Users can drag to rotate and see different sides
• 26 view options: All standard views + isometric corners + edge views
• Cross-platform stable: Pure Python - no C++ crashes
• Hover highlights: Visual feedback on interactive regions
• Qt integration: Uses PySide6 signals for clean event handling

Testing

• View cube displays correctly in CAD window
• Click on any face/corner/edge changes 3D view orientation
• Drag rotation works smoothly
• No crashes on Linux (tested on Ubuntu)

Related Issue

Fixes stability issues with C++ AIS_ViewCube causing crashes

Addresses: "C++ based cube has been enabled, which is leading to crashes (especially on Linux machines)"

• This PR is to make sure the issue gets solve under FOSSHack 2026.

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Note: Copyright to be transferred to Osdag Team at IIT Bombay as per task requirements.

[parthckaria]

Dear Manish
Thank you for your contribution. Are there any additional instructions to follow? I am encountering an error and have attached the log.
Crash-2026-03-16_12-03-26.log

[PredictiveManish]

I have made some changes according to logs given by you

[parthckaria]

Dear Manish
This issue got resolved. I am getting another crash when I am opening any module (currently opening Fin Plate Connection). We request that you sufficiently test this before raising a PR.
Crash-2026-03-17_10-39-35.log