How to check if a point is inside a polygon in JavaScript?

Geometric.js provides the pointInPolygon function, which uses ray casting to return a boolean. It handles basic polygon shapes efficiently, but for complex or self-intersecting polygons, additional validation might be needed.

Geometric.js vs Turf.js for 2D geometry?

Geometric.js is best for general Cartesian plane calculations like transformations and intersections, while Turf.js specializes in geospatial operations on Earth's surface with geographic projections. Choose based on whether your project is abstract math or map-related.

How to rotate a polygon around a specific point using Geometric.js?

Use the polygonRotate function, which takes the polygon, angle in degrees, and an optional origin point. If no origin is specified, it defaults to [0,0], allowing precise control over rotation centers.

Can Geometric.js handle 3D geometry or only 2D?

Geometric.js is strictly limited to 2D operations, as stated in its documentation. For 3D geometry, you would need to look at libraries like Three.js or other specialized tools.

Is Geometric.js good for collision detection in 2D games?

Yes, functions like lineIntersectsLine and polygonIntersectsPolygon can be used for basic collision detection. However, for high-performance real-time games, you might need more optimized libraries due to potential performance trade-offs.

How to calculate the area of a polygon with Geometric.js?

Use the polygonArea function, which returns the area as a number. You can optionally pass a boolean for signed area, making it useful for geometric computations in visualizations or measurements.

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Geometric.js

MITJavaScriptv2.2.5

A JavaScript library for performing 2D geometric calculations on points, lines, and polygons.

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1.0k stars51 forks0 contributors

What is Geometric.js?

Geometric.js is a JavaScript library for performing 2D geometric calculations on points, lines, and polygons. It provides functions for transformations, measurements, and relationship detection, solving the need for manual geometry math in visualization, gaming, or computational applications. The library uses simple array representations for primitives, making it easy to integrate into existing JavaScript projects.

Target Audience

JavaScript developers working on data visualization, computer graphics, game development, or computational geometry projects that require precise 2D geometric operations.

Value Proposition

Developers choose Geometric.js for its focused, dependency-free approach to 2D geometry, offering a comprehensive set of well-documented functions without the overhead of larger math or graphics libraries. Its simple API and clear examples make it accessible for both learning and production use.

Overview

A JavaScript library for doing geometry.

Use Cases

Best For

Calculating polygon areas and centroids in data visualizations
Detecting collisions and intersections in 2D games
Generating and manipulating geometric shapes for graphics applications
Performing point-in-polygon tests for geographic or UI hit detection
Creating convex hulls from point sets for computational geometry
Transforming and interpolating geometric primitives in animations

Not Ideal For

Applications requiring 3D geometric calculations, such as 3D modeling or WebGL visualizations
High-performance real-time simulations or games needing optimized, low-level geometry libraries
Projects needing advanced geometric primitives like curves, circles, or splines beyond basic polygons
Systems deeply integrated with frameworks like Three.js or D3 that have built-in geometry utilities

Pros & Cons

Pros

Clean, Intuitive API

Represents geometric primitives as simple arrays (e.g., [x,y] for points), making it easy to learn and integrate, as emphasized in the README's API structure.

Comprehensive 2D Toolkit

Offers a wide range of functions for transformations (rotate, scale), measurements (area, length), and relationships (intersections, containment), covering most common 2D geometry tasks.

No External Dependencies

The library is self-contained and lightweight, with no dependencies, aligning with its philosophy of simplicity and practicality for easy deployment.

Well-Documented with Examples

Each function includes source links and Observable notebook examples, providing clear, practical guidance that reduces implementation time.

Cons

Strictly 2D Focus

Lacks support for 3D geometry operations, limiting its utility in applications requiring spatial calculations beyond the plane, as admitted by its narrow scope.

Basic Data Representation

Relies on plain arrays without object-oriented or optimized data structures, which can lead to performance issues or cumbersome code for complex manipulations.

Missing Advanced Features

Does not include operations for curves, circles, or other non-polygonal shapes, focusing only on points, lines, and polygons, which restricts more sophisticated geometric work.

Frequently Asked Questions

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