29cfb8b63e
The finite precision of floating point computations can lead the coarse renderer into inconsistent tile intersections, which implies impossible line segments such as lines with gaps or double intersections. The winding number algorithm is sensitive to these errors which show up as incorrectly filled paths. This change forces all intersections to be consistent. First, the floating point top edge intersection test is removed; top edge intersections are completely determined by left edge intersections. Then, left edge intersections are inserted from the tile with the last top edge intersection. The next top edge is then fixed to be the last tile with a left edge intersection. More details in the patch comments. Fixes #23 Signed-off-by: Elias Naur <mail@eliasnaur.com> |
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| piet-gpu | ||
| piet-gpu-derive | ||
| piet-gpu-hal | ||
| piet-gpu-types | ||
| .gitignore | ||
| Cargo.lock | ||
| Cargo.toml | ||
| LICENSE-APACHE | ||
| LICENSE-MIT | ||
| README.md | ||
piet-gpu
This repo contains the new prototype for a new compute-centric 2D GPU renderer.
It succeeds the previous prototype, piet-metal.
Goals
The main goal is to answer research questions about the future of 2D rendering:
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Is a compute-centered approach better than rasterization (Direct2D)? How much so?
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To what extent do "advanced" GPU features (subgroups, descriptor arrays) help?
Another goal is to explore a standards-based, portable approach to GPU compute.
Non-goals
There are a great number of concerns that need to be addressed in production:
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Compatibility with older graphics hardware (including runtime detection)
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Asynchrony
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Swapchains and presentation
Notes
A more detailed explanation will come. But for now, a few notes. Also refer to Fast 2D rendering on GPU and linked blog posts for more information.
Why not gfx-hal?
It makes a lot of sense to use gfx-hal, as it addresses the ability to write kernel and runtime code once and run it portably. But in exploring it I've found some points of friction, especially in using more "advanced" features. To serve the research goals, I'm enjoying using Vulkan directly, through ash, which I've found does a good job tracking Vulkan releases. One example is experimenting with VK_EXT_subgroup_size_control.
The hal layer in this repo is strongly inspired by gfx-hal, but with some differences. One is that we're shooting for a compile-time pipeline to generate GPU IR on DX12 and Metal, while gfx-hal ships SPIRV-Cross in the runtime. To access Shader Model 6, that would also require bundling DXC at runtime, which is not yet implemented (though it's certainly possible).
Why not wgpu?
The case for wgpu is also strong, but it's even less mature. I'd love to see it become a solid foundation, at which point I'd use it as the main integration with druid.
In short, the goal is to facilitate the research now, collect the data, and then use that to choose a best path for shipping later.
License and contributions.
The piet-gpu project is dual-licensed under both Apache 2.0 and MIT licenses.
In addition, the shaders are provided under the terms of the Unlicense. The intent is for this research to be used in as broad a context as possible.
Contributions are welcome by pull request. The Rust code of conduct applies.