INE5420 - SGI: Interactive Graphics System

Python 3 + Tkinter interactive graphics system for INE5420 - Computer Graphics (UFSC).

Authors

Name	Student ID
Felipe Thaddeu Gassen	23100481
Augusto Schweitzer	23100475
Davi Ludvig Longen Machado	23100473

Task Progress

Task	What was built
1.1	2D display file, viewport transform, pan, zoom, canvas click capture
1.2	3x3 matrix transforms (translate, scale, rotate), color, composite queue
1.3	SCN pipeline, window rotation, rotation-aware navigation, Wavefront .obj I/O
1.4	Clipping (point, Cohen-Sutherland, Liang-Barsky, Sutherland-Hodgman), filled polygons, viewport border, .obj color/filled round-trip
1.5	Bézier curves (Curve2D) via matrix form with blending functions, multi-segment C1/G1 continuity, per-segment polyline clipping, .obj round-trip
1.6	B-Spline curves via uniform cubic forward differences, multi-segment rendering, .obj round-trip with curve_kind bspline tag
1.7	4×4 homogeneous transforms for 3D objects (translate, scale, rotate X/Y/Z, around-point); Object3D uses Matrix4 pipeline; geometric_center_3d; transform dialog detects 3D and exposes dz, sz, axis selector
1.8	3D projection pipeline with parallel and perspective modes, configurable COP/focal distance, near-plane clipping before perspective divide
1.9	Bicubic surface meshes from sets of 3 matrices 4×4 (Gx, Gy, Gz), sampled with Hermite or B-Spline characteristic matrices and rendered through the 3D wireframe/projection pipeline
1.10	Bicubic surface mesh sampling via forward differences: C = M·G·Mᵀ, DD = E(ds)·C·E(dt)ᵀ, rendering both surface curve families
1.11	Pixel Shading — software rasterization pipeline with Z-buffer (wireframe/solid/Phong modes) and per-fragment Phong shading with interpolated normals

Quick start

Linux / macOS

python3 -m venv .venv
source .venv/bin/activate
pip install -e .
python -m sgi

Windows (PowerShell)

python -m venv .venv
.venv\Scripts\Activate.ps1
pip install -e .
python -m sgi

Linux: install python3-tk from the system package manager if Tkinter is missing (sudo apt install python3-tk on Debian/Ubuntu).

Optional: faster rasterizer (recommended)

Install Pillow to enable the fast display path (~5 ms/frame instead of ~20 ms):

pip install -e ".[rasterizer]"

Without Pillow the rasterizer still works via a PPM temp-file fallback, just slightly slower.

Sample objects

• objects/penger.obj: Penger penguin model converted to SGI Object3D wireframe from Max-Kawula/penger-obj, licensed under the Penger Public License.

Architecture

src/sgi/
├── core/
│   ├── bezier.py             # Bézier matrix eval, C1 segmentation, polyline
│   ├── bspline.py            # B-Spline forward differences
│   ├── clipping.py           # Point, line (C-S, L-B), polygon (S-H), curve polyline
│   ├── display_file.py       # Object storage
│   ├── geometry.py           # Point2D, Point3D
│   ├── obj_io.py             # Wavefront .obj read/write (2D + 3D round-trip)
│   ├── objects.py            # GraphicObject, Object3D, ObjectType
│   ├── parsing.py            # Coordinate parsing
│   ├── projection.py         # Parallel/perspective projection and near-plane clipping
│   ├── rasterizer.py         # Framebuffer, Z-buffer, Phong shading (software renderer)
│   ├── surface.py            # Bicubic surface patch evaluation and mesh sampling
│   ├── transforms.py         # 3x3 (2D) and 4x4 (3D) homogeneous matrices
│   └── window_viewport.py    # Window, Viewport, SCN pipeline
├── ui/
│   ├── canvas_renderer.py    # Drawing + viewport border (Tkinter path)
│   ├── dev_tools.py          # Debug/test popup menu (3D spin, rasterizer tests, …)
│   ├── main_window.py        # Tkinter shell and canvas/footer orchestration
│   ├── main_window_form.py   # New-object form and coordinate capture
│   ├── main_window_sidebar.py # Display-file sidebar, navigation, file/render actions
│   ├── raster_renderer.py    # Bridge: mapped_objects → Framebuffer (wireframe/solid/Phong)
│   └── transform_dialog.py   # Transform/rename dialog (2D and 3D modes)
└── app.py                    # Application controller

Tests are grouped by layer:

tests/
├── core/         # Geometry, clipping, transforms, parsing, OBJ and surfaces
├── integration/  # Application/projection pipelines with fake or real UI shells
└── ui/           # Tk widgets, renderer and dialog behavior

Docs

• Usage guide
• Development & CI
• Branching workflow