FixedMathSharp

A deterministic fixed-point math library for .NET.
Built for simulations, games, and physics-heavy code that needs reliable results without floating-point drift.

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🛠️ Key Features

• Deterministic fixed-point arithmetic: Consistent results across platforms with Fixed64.
• Core math types included: Vector2d, Vector3d, FixedQuaternion, Fixed3x3, and Fixed4x4.
• Spatial helpers: BoundingBox, BoundingSphere, and BoundingArea for lightweight bounds checks.
• Shared math utilities: Common math and trigonometry helpers via FixedMath and FixedTrigonometry.
• Deterministic RNG: DeterministicRandom for repeatable procedural generation and simulations.
• Flexible packaging: Use the default package with MemoryPack, or the NoMemoryPack package when you want the same API without that dependency.
• Broad .NET compatibility: Targets modern .NET while remaining friendly to engine and tooling workflows.

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🚀 Installation

For most .NET projects, start with the standard package:

dotnet add package FixedMathSharp

Non-Unity Projects

Choose the package that fits your runtime:

Package	Best for	Install
FixedMathSharp	Most .NET applications. Includes built-in MemoryPack support.	dotnet add package FixedMathSharp
FixedMathSharp.NoMemoryPack	Projects that want the same math API without a MemoryPack dependency, including custom serializer setups and Burst AOT-sensitive workflows.	dotnet add package FixedMathSharp.NoMemoryPack

If you're using FluentAssertions in your test project, the companion assertions package is available here: FixedMathSharp.FluentAssertions

Build From Source

Clone the repository and build locally:

git clone https://github.com/mrdav30/FixedMathSharp.git
dotnet restore
dotnet build --configuration Debug --no-restore

You can also reference the project directly or consume the generated package artifacts in your own build process.

Package Variants

The published NuGet packages map directly to the source-build configurations below.

If you build from source, the repository also provides matching release configurations:

• Release builds the standard FixedMathSharp package and archives.
• ReleaseNoMemoryPack builds the FixedMathSharp.NoMemoryPack package and archives.

If you use Unity Burst AOT, prefer the NoMemoryPack variant.

Unity Integration

FixedMathSharp is maintained as a separate Unity package. For Unity-specific implementations, refer to:

🔗 FixedMathSharp-Unity Repository.

If you are evaluating this .NET package for Unity-adjacent tooling using Burst AOT, prefer FixedMathSharp.NoMemoryPack.

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📖 Usage Examples

Basic Arithmetic with Fixed64

Fixed64 a = new Fixed64(1.5);
Fixed64 b = new Fixed64(2.5);
Fixed64 result = a + b;
Console.WriteLine(result); // Output: 4.0

Vector Operations

Vector3d v1 = new Vector3d(1, 2, 3);
Vector3d v2 = new Vector3d(4, 5, 6);
Fixed64 dotProduct = Vector3d.Dot(v1, v2);
Console.WriteLine(dotProduct); // Output: 32

Quaternion Rotation

FixedQuaternion rotation = FixedQuaternion.FromAxisAngle(Vector3d.Up, FixedMath.PiOver2); // 90 degrees around Y-axis
Vector3d point = new Vector3d(1, 0, 0);
Vector3d rotatedPoint = rotation.Rotate(point);
Console.WriteLine(rotatedPoint); // Output: (0, 0, -1)

Matrix Transformations

Fixed4x4 matrix = Fixed4x4.Identity;
Vector3d position = new Vector3d(1, 2, 3);
matrix.SetTransform(position, Vector3d.One, FixedQuaternion.Identity);
Console.WriteLine(matrix);

Bounding Shapes and Intersection

BoundingBox box = new BoundingBox(new Vector3d(0, 0, 0), new Vector3d(5, 5, 5));
BoundingSphere sphere = new BoundingSphere(new Vector3d(3, 3, 3), new Fixed64(1));
bool intersects = box.Intersects(sphere);
Console.WriteLine(intersects); // Output: True

Trigonometry Example

Fixed64 angle = FixedMath.PiOver4; // 45 degrees
Fixed64 sinValue = FixedTrigonometry.Sin(angle);
Console.WriteLine(sinValue); // Output: ~0.707

Deterministic Random Generation

Use DeterministicRandom when you need reproducible random values across runs, worlds, or features.
Streams are derived from a seed and remain deterministic regardless of threading or platform.

// Simple constructor-based stream:
var rng = new DeterministicRandom(42UL);

// Deterministic integer:
int value = rng.Next(1, 10); // [1,10)

// Deterministic Fixed64 in [0,1):
Fixed64 ratio = rng.NextFixed6401();

// One stream per “feature” that’s stable for the same worldSeed + key:
var rngOre = DeterministicRandom.FromWorldFeature(worldSeed: 123456789UL, featureKey: 0xORE);
var rngRivers = DeterministicRandom.FromWorldFeature(123456789UL, 0xRIV, index: 0);

// Deterministic Fixed64 draws:
Fixed64 h = rngOre.NextFixed64(Fixed64.One);                      // [0, 1)
Fixed64 size = rngOre.NextFixed64(Fixed64.Zero, 5 * Fixed64.One); // [0, 5)
Fixed64 posX = rngRivers.NextFixed64(-Fixed64.One, Fixed64.One);  // [-1, 1)

// Deterministic integers:
int loot = rngOre.Next(1, 5); // [1,5)

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📦 Library Structure

• Fixed64 Struct: Core Q32.32 fixed-point scalar type.
• Vector2d and Vector3d Structs: 2D and 3D vector math.
• FixedQuaternion Struct: Deterministic quaternion rotations.
• Fixed4x4 and Fixed3x3: Matrix math for transforms and orientation.
• IBound Interface and bounds types: BoundingBox, BoundingArea, and BoundingSphere for intersection, containment, and projection queries.
• FixedMath and FixedTrigonometry: Shared numeric and trigonometric helpers.
• DeterministicRandom Struct: Seedable, allocation-free RNG for repeatable procedural generation.

Fixed64 Struct

Fixed64 is the center of the library: a deterministic fixed-point number type backed by integer arithmetic. It is the type used throughout the vector, matrix, quaternion, bounds, and helper APIs.

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⚡ Performance Considerations

FixedMathSharp is optimized for high-performance deterministic calculations:

• Inline methods and bit-shifting optimizations keep hot paths lightweight.
• Deterministic arithmetic avoids floating-point drift in lockstep or replay-driven systems.
• Fuzzy equality helpers are available where precision tolerances are useful.

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🧪 Testing and Validation

The library is covered by xUnit tests for core arithmetic, vectors, bounds, serialization, and deterministic random behavior. Fuzzy comparisons are used where a tolerance-based check is more appropriate than exact equality.

To run the tests:

dotnet test --configuration Debug

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🛠️ Compatibility

• .NET Standard 2.1
• .NET 8
• Unity 2020+ (via FixedMathSharp-Unity)
• Cross-Platform Support (Windows, Linux, macOS)

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🤝 Contributing

We welcome contributions! Please see our CONTRIBUTING guide for details on how to propose changes, report issues, and interact with the community.

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👥 Contributors

• mrdav30 - Lead Developer
• Contributions are welcome! Feel free to submit pull requests or report issues.

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💬 Community & Support

For questions, discussions, or general support, join the official Discord community:

👉 Join the Discord Server

For bug reports or feature requests, please open an issue in this repository.

We welcome feedback, contributors, and community discussion across all projects.

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📄 License

This project is licensed under the MIT License.

See the following files for details:

• LICENSE – standard MIT license
• NOTICE – additional terms regarding project branding and redistribution
• COPYRIGHT – authorship information