A (thoroughly) parallelized experimental Rust vector-graphics renderer with both a software (CPU) and hardware (GPU) back-end having the following goals, in this order:
- Portability; supporting Fuchsia, Linux, macOS, Windows, Android & iOS.
- Performance; making use of compute-focused pipeline that is highly parallelized both at the instruction-level and the thread-level.
- Simplicity; implementing an easy-to-understand 4-stage pipeline.
- Size; minimizing the number of dependencies and focusing on vector-graphics only.
It relies on Rust's SIMD auto-vectorization/intrinsics and Rayon to have good performance on the CPU, while using WebGPU (wgpu) to take advantage of the GPU.
Getting started
Add the following to your Cargo.toml dependencies:
forma = { version = "0.1.0", package = "forma-render" }4-stage Pipeline
| 1. Curve flattening | 2. Line segment rasterization | 3. Sorting | 4. Painting |
|---|---|---|---|
| Bézier curves | line segments | pixel segments | sorted pixel segments, old tiles |
| ⬇️⬇️⬇️ | ⬇️⬇️⬇️ | ⬇️⬇️⬇️ | ⬇️⬇️⬇️ |
| line segments | pixel segments | sorted pixel segments | freshly painted tiles |
Implementation Highlights ✨
Here are a few implementation highlights that make forma stand out from commonly used vector renderers.
Curvature-aware flattening
All higher cubic Béziers are approximated by quadratic ones, then, in parallel, flattened to line segments according to their curvature. This [technique] was developed by Raph Levien. [technique]: https://raphlinus.github.io/graphics/curves/2019/12/23/flatten-quadbez.htmlCheap translations and rotations
Translations and rotations can be rendered without having to re-flatten the curves, all the while maintaining full quality.Parallel pixel grid intersection
Line segments are transformed into pixel segments by intersecting them with the pixel grid. We developed a simple method that performs this computation in *O(1)* and which is run in parallel.Efficient sorting
We ported [crumsort] to Rust and parallelized it with Rayon, delivering improved performance over its pdqsort implementation for 64-bit random data. Scattering pixel segments with a sort was inspired from Allan MacKinnon's work on [Spinel]. [crumsort]: https://github.com/google/crumsort-rs [Spinel]: https://cs.opensource.google/fuchsia/fuchsia/+/main:src/graphics/lib/compute/spinel/Update only the tiles that change (currently CPU-only)
We implemented a fail-fast per-tile optimizer that tries to skip the painting step entirely. A similar approach could also be tested on the GPU.| Animation as it appears on the screen | Updated tiles only |
|---|---|
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You can run the demo above with:
cargo run --release -p demo -- spaceshipSimilar Projects
forma draws heavy inspiration from the following projects:
- [Spinel], with a Vulkan 1.2 back-end
- vello, with a wgpu back-end
Example
You can use the included demo example to render a few examples, one of which is a non-compliant & incomplete SVG renderer:
cargo run --release -p demo -- svg assets/svgs/paris-30k.svgIt renders enormous SVGs at interactive framerates, even on CPU: (compare to your web browser)
(Currently) Missing Pieces 🧩
Since this project is work-in-progress, breakage in the API, while not drastic, is expected. The performance on the GPU back-end is also expected to improve especially on mobile where performance is known to be poor and where the CPU back-end is currently advised instead.
Other than that:
- Automated layer ordering
- Strokes
- More color spaces for blends & gradients
- Faster GPU sorter
- Use of
f16for great mobile GPU performance
Note
This is not an officially supported Google product.