Geometric Modeling

A cross-platform C++ mesh viewer built around a half-edge data structure.

This project loads Wavefront OBJ meshes, represents their topology with half-edges, and exposes common geometry-processing operations through an OpenGL viewer. The implementation focuses on topology invariants, portable builds, and visible before/after results.

Highlights

• OBJ loading with automatic twin reconstruction and mesh normalization
• Per-face and per-vertex normal computation
• View-dependent silhouette detection
• Convex and concave polygon triangulation using ear clipping
• Surface-of-revolution mesh generation
• Shortest-edge-collapse simplification
• Catmull-Clark subdivision with boundary handling
• Automated half-edge invariant tests

Results

Operation	Before	After
Concave triangulation
Edge-collapse simplification
Catmull-Clark subdivision

Additional captures are available in docs/images.

Architecture

TP1/MeshViewerCMake/
|-- myMesh.*           Half-edge ownership and geometry algorithms
|-- myHalfedge.*       Directed-edge topology
|-- myFace.*           Face adjacency and normal computation
|-- myVertex.*         Vertex geometry and incident-edge access
|-- main.cpp           OpenGL/GLUT viewer and interaction
`-- test_mesh.cpp      Topology and algorithm regression tests

mesh_core contains the geometry implementation without a window-system dependency. The viewer adds OpenGL, GLEW, GLM, and GLUT on top of that core.

Build

Requirements:

• CMake 3.20 or newer
• A C++17 compiler
• OpenGL, GLEW, GLM, and GLUT/FreeGLUT

Install dependencies:

# Ubuntu / Debian
sudo apt-get install cmake g++ libgl1-mesa-dev libglew-dev libglm-dev freeglut3-dev

# macOS
brew install cmake glew glm

# Windows with vcpkg
vcpkg install glew:x64-windows glm:x64-windows freeglut:x64-windows

Configure, build, and test:

cmake -S TP1/MeshViewerCMake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build --config Release
ctest --test-dir build -C Release --output-on-failure

On Windows, also pass the vcpkg toolchain file during configuration:

cmake -S TP1/MeshViewerCMake -B build `
  -DCMAKE_TOOLCHAIN_FILE="$env:VCPKG_ROOT/scripts/buildsystems/vcpkg.cmake" `
  -DVCPKG_TARGET_TRIPLET=x64-windows

Launch MeshViewer from the build directory. Right-click inside the window to open the operation menu.

To work only on the geometry core and tests without installing graphics dependencies, disable the viewer:

cmake -S TP1/MeshViewerCMake -B build -DGEOMETRIC_MODELING_BUILD_VIEWER=OFF
cmake --build build --config Release
ctest --test-dir build -C Release --output-on-failure

Test coverage

The regression executable validates loading, twin reciprocity, face-loop consistency, triangulation, simplification, subdivision, and open-boundary behavior. CI builds the project and runs the suite on Linux, macOS, and Windows.

Project context

This project was developed as an academic geometric-modeling assignment. AI tools were used for targeted portability troubleshooting and as a learning aid; the implementation choices, integration, and validation remain the author's.

License

MIT - copyright Allan Seddi.