Crate lyon [−] [src]
2d rendering on the GPU in rust.
Crates
- - lyon_tessellation - Path tessellation routines.
- - lyon_path_builder - Tools to facilitate building paths.
- - lyon_path_iterator - Tools to facilitate iteratring over paths.
- - lyon_path - A simple optional path data structure, provided for convenience.
- - lyon_bezier - Cubic and quadratic 2d bézier math.
- - lyon_svg - Create paths using SVG's path syntax.
- - lyon_extra - Additional testing and debugging tools.
- - lyon_core - Common types to most lyon crates (mostly for internal use, reexported by the other crates).
This crate is a meta-crate, reexporting the crates listed above.
Additional documentation and links
- very basic gfx-rs example.
- advanced gfx-rs example.
- There is some useful documentaion on the project's wiki.
- The source code is available on the project's git repository.
- Interested in contributing? Pull requests are welcome. If you would like to help but don't know what to do specifically, have a look at the github issues, some of which are tagged as easy.
Examples
Tessellating a rounded rectangle
The lyon_tessellation
crate provides a collection of tessellation routines
for common shapes such as rectangles and circles. Let's have a look at how
to obtain the fill tessellation a rectangle with rounded corners:
extern crate lyon; use lyon::math::rect; use lyon::tessellation::VertexBuffers; use lyon::tessellation::basic_shapes::*; use lyon::tessellation::geometry_builder::simple_builder; fn main() { let mut geometry = VertexBuffers::new(); let tolerance = 0.1; fill_rounded_rectangle( &rect(0.0, 0.0, 100.0, 50.0), &BorderRadii { top_left: 10.0, top_right: 5.0, bottom_left: 20.0, bottom_right: 25.0, }, tolerance, &mut simple_builder(&mut geometry), ); // The tessellated geometry is ready to be uploaded to the GPU. println!(" -- {} vertices {} indices", geometry.vertices.len(), geometry.indices.len() ); }
Building and tessellating an arbitrary path
extern crate lyon; use lyon::math::point; use lyon::path::Path; use lyon::path_builder::*; use lyon::path_iterator::PathIterator; use lyon::tessellation::{FillTessellator, FillOptions, VertexBuffers}; use lyon::tessellation::geometry_builder::simple_builder; fn main() { // Build a Path. let mut builder = Path::builder(); builder.move_to(point(0.0, 0.0)); builder.line_to(point(1.0, 0.0)); builder.quadratic_bezier_to(point(2.0, 0.0), point(2.0, 1.0)); builder.cubic_bezier_to(point(1.0, 1.0), point(0.0, 1.0), point(0.0, 0.0)); builder.close(); let path = builder.build(); // Will contain the result of the tessellation. let mut geometry = VertexBuffers::new(); let mut tessellator = FillTessellator::new(); { let mut geom_builder = simple_builder(&mut geometry); let tolerance = 0.1; // Compute the tessellation. tessellator.tessellate_flattened_path( path.path_iter().flattened(tolerance), &FillOptions::default(), &mut geom_builder ).unwrap(); } // The tessellated geometry is ready to be uploaded to the GPU. println!(" -- {} vertices {} indices", geometry.vertices.len(), geometry.indices.len() ); }
What is the tolerance variable in these examples?
The tessellator operates on flattened paths (that only contains line segments) so we have to approximate the curves segments with sequences of line segments. To do so we pick a tolerance threshold which is the maximum distance allowed between the curve and its approximation. The documentation of the lyon_bezier crate provides more detailed explanations about this tolerance parameter.
Rendering the tessellated geometry
Lyon does not provide with any GPU abstraction or rendering backend (for now). It is up to the user of this crate to decide whether to use OpenGL, vulkan, gfx-rs, glium, or any low level graphics API and how to render it. The basic and advanced gfx-rs examples can be used to get an idea of how to render the geometry (in this case using gfx-rs).
Which crates do I need?
The meta-crate (lyon
) mostly reexports the other lyon crates for convenience.
extern crate lyon; use lyon::tessellation::FillTessellator;
Is equivalent to:
extern crate lyon_tessellation; use lyon_tessellation::FillTessellator;
- The
lyon_tessellation
crate is the most interesting crate so is what most people using lyon are interested in. The tessellation algorithms don't depend on a specific data structure. Instead they work on iterators of path. When using thelyon_tessellation
crate you'll almost always want to use thelyon_path_iterator
crate as well. - The
lyon_path_iterator
crate contains a colletion of tools to chain iterators of path events. These adapters are very useful to convert an iterator of SVG events (which contains various types of curves in relative and absolute coordinates) into iterator of simpler path events (every thing in absolute coordinates) all the way to flattened events (only line segments in absolute corrdinates). - The
lyon_path
crate is completely optional. It contains a path data structure which work with thelyon_path_iterator
(and thus works withlyon_tessellation
) andlyon_path_builder
crates. Various examples use it but anyone can implement a custom path data structure that works with the tessellators as long as it provides an iterator of path events. - The
lyon_path_builder
crate is also optional, but provide useful abstractions to build path objects from sequences of function calls likemove_to
,cubic_bezier_to
, etc. Just likelyon_path_iterator
this crate provides adapters between the different types of path events, making it easy to use the full set of SVG events to build a path object that does not actually support all of them by converting events to lower level primitives on the fly. - The
lyon_bezier
crate is really standalone as it does not depend on any otherlyon_*
crate. It implements useful quadratic and cubic bezier curve math, including the flattening algorithm that is used bylyon_path_iterator
andlyon_path_builder
. - The
lyon_svg
crate contains utilities to interface with SVG. At the moment it is mostly a collection of wrappers around the excellentsvgparser
crate. - The
lyon_core
crate contains internal details that are useful to all other lyon crates (exceptlyon_bezier
). It is reexported by all crates and you should not have to interact directly with it.
These crates are not very big, it's usually fine for most use-case to simply import the lyon
meta-crate, unless you are only interested in the bezier tools.
Reexports
pub extern crate lyon_core; |
pub extern crate lyon_path; |
pub extern crate lyon_path_builder; |
pub extern crate lyon_path_iterator; |
pub extern crate lyon_tessellation; |
pub extern crate lyon_bezier; |
pub extern crate lyon_extra; |
pub extern crate lyon_svg; |
pub use lyon_core::*; |
Modules
bezier | |
extra | |
path | |
path_builder | |
path_iterator | |
svg | |
tessellation |