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Crate lyon_tess2

Crate lyon_tess2 

Source
Expand description

Alternative fill tessellation implementation using libtess2.

§Lyon libtess2 wrapper

This crate provides an alternative path fill tessellator implemented as a wrapper of the libtess2 C library.

The goal of this crate is to provide an alternative tessellator for the potential cases where lyon_tessellation::FillTessellator is lacking in features or robustness, and have something to compare the latter against.

§Comparison with lyon_tessellation::FillTessellator

Advantages:

  • Supports the NonZero fill rule.
  • More robust against precision errors when paths have many self intersections very close to each other.

Disadvantages:

  • About twice slower than lyon_tessellation’s fill tessellator.
  • Does not support computing vertex normals.
  • Wrapper around a C library (as opposed to pure rust with no unsafe code).

§API

In order to avoid any overhead, this crate introduces the FlattenedPath type which stores already-flattened paths in the memory layout expected by libtess2. Instead of working with a GeometryBuilder like the tessellators in lyon_tessellation, this tessellator uses a GeometryReceiver trait that corresponds to the way libtess2 exposes its output.

§Example

extern crate lyon_tess2 as tess2;
use tess2::{FillTessellator, FillOptions};
use tess2::math::{Point, point};
use tess2::path::Path;
use tess2::path::builder::*;
use tess2::geometry_builder::*;

fn main() {
    // Create a simple path.
    let mut path_builder = Path::builder();
    path_builder.begin(point(0.0, 0.0));
    path_builder.line_to(point(1.0, 2.0));
    path_builder.line_to(point(2.0, 0.0));
    path_builder.line_to(point(1.0, 1.0));
    path_builder.end(true);
    let path = path_builder.build();

    // Create the destination vertex and index buffers.
    let mut buffers: VertexBuffers<Point, u16> = VertexBuffers::new();

    {
        // Create the tessellator.
        let mut tessellator = FillTessellator::new();

        // Compute the tessellation.
        let result = tessellator.tessellate(
            &path,
            &FillOptions::default(),
            &mut BuffersBuilder::new(&mut buffers, Positions)
        );
        assert!(result.is_ok());
    }
    println!("The generated vertices are: {:?}.", &buffers.vertices[..]);
    println!("The generated indices are: {:?}.", &buffers.indices[..]);

}

Re-exports§

pub extern crate tess2_sys;
pub extern crate lyon_tessellation as tessellation;
pub use tessellation::geom;
pub use tessellation::path;

Modules§

flattened_path
geometry_builder
math
f32 version of the lyon_geom types used everywhere. Most other lyon crates reexport them.

Structs§

FillOptions
Parameters for the fill tessellator.
FillTessellator
A fill tessellator implemented on top of libtess2.