MiniCAD

A personal project to explore CAD geometry, computational geometry, DXF parsing, coordinate transformations, and 2D CAD visualization using C# and .NET. This project is being developed from scratch as a learning project with the long-term goal of building a small CAD geometry/kernel-like system and a simple CAD viewer.

🚧 Work in Progress

MiniCAD is still under active development. Many features are incomplete and the architecture will continue to evolve as new geometry and CAD concepts are implemented.

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MiniCAD Viewer

MiniCAD.Viewer/ViewerUI.png

Procedure

Mathematics
    ↓
Computational Geometry
    ↓
CAD Data Structures
    ↓
DXF Parsing
    ↓
Coordinate Transformation
    ↓
Rendering
    ↓
Interactive Viewer

The current viewer can load a DXF file and display supported entities such as Lines and Circles.

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Current Features

Geometry

Currently implemented or under development:

• Point
• Vector
• Line
• Circle
• Triangle
• Polygon
• BoundingBox
• 2D Matrix transformations
• Translation
• Rotation
• Scaling
• Mirroring
• Distance calculations
• Dot product
• Cross product
• Vector normalization
• Angle calculations
• Geometric containment tests
• Intersection calculations

DXF

A basic DXF reader is currently being developed.

Current functionality includes:

• Reading ASCII DXF files
• Parsing DXF group code/value pairs
• Reading LINE entities
• Reading CIRCLE entities
• Loading multiple entities from a single DXF file

Example:

DXF
 ├── LINE
 ├── CIRCLE
 ├── LINE
 ├── CIRCLE
 └── ...

These entities are converted into MiniCAD geometry objects and passed to the viewer.

Viewer

A simple WinForms-based 2D CAD viewer is currently implemented.

Current functionality:

• Open DXF files through a file dialog
• Display DXF Lines
• Display DXF Circles
• World-to-screen coordinate transformation
• Camera zoom
• Camera offset
• Bounding-box based Fit All
• Basic viewer UI

Architecture

The project is currently organized into several components:

MiniCAD
│
├── MiniCAD.Geometry
│   ├── Point.cs
│   ├── Vector.cs
│   ├── Line.cs
│   ├── Circle.cs
│   ├── Triangle.cs
│   ├── Polygon.cs
│   ├── BoundingBox.cs
│   └── Matrix2D.cs
│
├── MiniCAD.Geometry.Tests
│   ├── PointTests.cs
│   ├── VectorTests.cs
│   └── ...
│
├── MiniCAD.dxf
│   ├── DxfReader.cs
│   ├── DxfPair.cs
│   └── Samples
│
└── MiniCAD.Viewer
    ├── Form1.cs
    ├── Camera.cs
    └── ...

The overall architecture is evolving as the project grows.

Coordinate Transformation

MiniCAD uses a separation between world coordinates and screen coordinates.

World Coordinates
       │
       ▼
   Camera
       │
       ▼
World → Screen
       │
       ▼
   WinForms
       │
       ▼
     Viewer

The current camera supports:

• Zoom
• X/Y offset
• World-to-screen transformation
• Fit All calculation

The goal is to gradually evolve this into a more complete CAD-style camera/navigation system.

Testing

The geometry library is being developed using automated unit tests with xUnit.

Example:

[Theory]
[InlineData(1, 0, 1, 0, 0)]
[InlineData(1, 0, 0, 1, 90)]
[InlineData(1, 0, -1, 0, 180)]
[InlineData(0, 1, 1, 0, 0)]
public void AngleTo(double x1, double y1, double x2, double y2, double expected)
{
    Vector v1 = new Vector(x1, y1);
    Vector v2 = new Vector(x2, y2);
    double actualRadian = v1.AngleTo(v2);
    double actual = actualRadian * 180 / Math.PI;

    Assert.Equal(expected, actual, 0.001);
}

The test suite is being expanded as new geometry functionality is implemented.

What it is covering

This project is primarily a hands-on exploration of the concepts behind CAD and geometry software.

Areas being studied include:

• Computational Geometry
• Linear Algebra
• Numerical Tolerance
• Coordinate Systems
• Geometric Transformations
• Bounding Boxes
• Intersection Algorithms
• Curve Mathematics
• CAD Data Formats
• DXF
• 2D Rendering
• Camera Systems
• Mesh Geometry
• Boundary Representation (B-Rep)
• NURBS

Roadmap

Phase 1 - Basic Geometry

• Point
• Vector
• Line
• Circle
• Basic transformations
• BoundingBox
• Matrix2D
• UnitTests

Phase 2 - DXF

• DXF file reading
• DXF pair parsing
• LINE
• CIRCLE
• ARC
• POLYLINE
• SPLINE
• DXF Writer

Phase 3 - Viewer

• Windows Forms viewer
• DXF loading
• Basic rendering
• Camera
• World-to-screen transformation
• Zoom
• Offset / Pan
• Mouse interaction
• Selection
• Grid
• Coordinate system
• Layers

Phase 4 — Computational Geometry

• Polygon.Contains
• Triangle.Contains
• Line intersection
• Line-Circle intersection
• Circle-Circle intersection
• Convex Hull
• Curve intersection
• Boolean geometry

Phase 5 — Advanced Geometry

• Bezier Curves
• Mesh
• Half-edge data structure
• B-Rep
• NURBS
• Surface evaluation

🚧 More features will be added continuously!