Abstract
A Python utility that takes a high-contrast key-style image, runs OpenCV contour detection, and writes the resulting 2D geometry as an OBJ file for 3D modeling tools. The labeled contour preview is the main debugging aid, letting you verify detection before committing to an export.
1. What This Is
The project bridges computer vision and 3D graphics tooling. It loads a source image, detects the dominant contour with OpenCV, converts the pixel-space coordinates into an ordered vertex list, and serialises the result as a standard OBJ file. A labeled preview renders the detected points on the source image so the detection can be inspected visually before the model is written to disk.
2. How It Works
The pipeline is linear: image in, OBJ out. OpenCV handles loading, preprocessing, and contour detection; NumPy handles the coordinate arrays; a small writer emits the OBJ text file.
| # | Stage | Input | Tool | Output |
|---|---|---|---|---|
| 01 | Load & preprocess | Source image file | OpenCV | Prepared array |
| 02 | Contour detection | Prepared array | OpenCV | Contour point set |
| 03 | Coordinate ordering | Contour points | NumPy | Ordered vertex list |
| 04 | Labeled preview | Vertices + source image | OpenCV | Annotated image |
| 05 | OBJ export | Ordered vertices | Python file I/O | .obj file |
3. Constraints
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High-contrast source assumption
Contour detection is tuned for key-style images with a single dominant shape. Noisy or low-contrast inputs will produce fragmented or missing contours.
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Flat 2D geometry only
The OBJ output is a planar vertex ring. There is no extrusion, thickness, or surface-normal generation, so the model is a flat outline rather than a solid part.
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No multi-contour handling
The pipeline targets a single significant contour. Images with multiple shapes or internal holes are not decomposed or merged.
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No output validation
The OBJ file is written without a round-trip parse or vertex-count sanity check, so a malformed contour can silently produce a broken model.
4. Next
- a. Add Douglas-Peucker simplification to reduce vertex count before export.
- b. Support multiple contours and internal holes (key slots, cutouts).
- c. Add a simple extrusion step so the OBJ contains faces and normals, not just a vertex ring.
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