tess2-rust

A pure Rust port of libtess2 — the SGI tessellation library refactored by Mikko Mononen. This is an exact mathematical 1-to-1 port of the C library, preserving all algorithmic behavior including edge cases. Zero external dependencies. No unsafe code. WASM-compatible.

Try the Interactive Demo — 6 interactive pages running entirely in your browser via WebAssembly.

Crate listing: tess2-rust on crates.io.

tess2-rust Interactive Demo — Basic Shapes with tessellation visualization

Features

Polygon Tessellation — tessellate complex polygons into triangles, quads, or boundary contours
Winding Rules — five rules (Odd, NonZero, Positive, Negative, AbsGeqTwo) for flexible fill control
Multiple Output Types — triangles, connected polygons of configurable size, and boundary contours
Self-Intersecting Polygons — handles self-intersections, overlapping contours, and degenerate geometry
No Unsafe Code — zero unsafe blocks in the entire codebase
Zero Dependencies — no external runtime dependencies
WASM-Compatible — compiles to WebAssembly for browser-based usage

Interactive Demo

All 6 demo pages run in-browser via WebAssembly with no server-side processing:

Page	Description
Basic Shapes	Triangles, quads, pentagons, and concave shapes — the building blocks of tessellation
Polygon with Hole	Outer/inner contour reversal and hole detection
Winding Rules	All five rules compared on stars, bowties, nested shapes, and overlapping polygons
Output Modes	Triangles, quads, connected polygons, and boundary contours
Shape Gallery	Real-world datasets — dude, tank, spaceship, and more from poly2tri and GLU test suites
Interactive Editor	Draw your own polygons and watch them tessellate in real time

Browse the demos →

Quick Start

Add this to your Cargo.toml:

[dependencies]

tess2-rust = "1.0"

use tess2_rust::{Tessellator, WindingRule, ElementType};

let mut tess = Tessellator::new();
tess.add_contour(&[0.0, 0.0, 1.0, 0.0, 1.0, 1.0, 0.0, 1.0]);
tess.tessellate(WindingRule::Odd, ElementType::Polygons, 3);

let vertices = tess.vertices();
let elements = tess.elements();

Winding Rules

Odd — Fill regions with odd winding number (like even-odd fill)
NonZero — Fill regions with non-zero winding number
Positive — Fill regions with positive winding number
Negative — Fill regions with negative winding number
AbsGeqTwo — Fill regions with winding number >= 2 in absolute value

Development

Building & Testing

cargo build

cargo test                    # 138 tests

cargo clippy -- -D warnings

Running the Demo Locally

cd demo

bun install

bun run dev

Then open http://localhost:3000 in your browser.

License

SGI Free Software License B (functionally equivalent to MIT). See LICENSE.

Acknowledgments

Mikko Mononen — Author of the libtess2 refactoring of the SGI code
SGI — Original tessellation library from the OpenGL Sample Implementation
Ported by Lars Brubaker, sponsored by MatterHackers
Ported using Claude by Anthropic

tess2-rust 1.0.0