UI CPU clipping implementation supporting rotation and scaling#24148
UI CPU clipping implementation supporting rotation and scaling#24148ickshonpe wants to merge 31 commits into
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`CalculatedClip` is now an enum with `Rects` and `FullyClipped` variants. `Rects` holds a list of `Rect` in node local coords and `Affine2` world-to-local transform. `bevy_ui_render` has a new `clipping` module with a `clip_polygon` function that intersects UI elements with the clipping rects and chops off the non-visible regions and returns a list of vertices that forms a triangle fan. New example `overflow_transform`.
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| //! Demonstrates nested transformed UI clipping. | |||
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I think this probably belongs in testbed. It's a great test, but not very educational.
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Yeah maybe, I might expand it further though.
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kk! It's also fancy enough that I don't mind it being in the main examples.
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
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…into overflow-transform
ickshonpe
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…ate function with the value taken from the parley `Layout`, not the caller. * `TextLayoutInfo::size` should be in physical pixels, like the rest of the layout properties, and, again, set b he text layout update function, not the caller.
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| //! Demonstrates nested transformed UI clipping. | |||
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This could be clearer. We should actually describe what this supports, and why it matters for users.
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| [[example]] | ||
| name = "overflow_transform" |
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This is a weak name: at a glance even I have trouble understanding what this is trying to teach or why I might care.
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I've finally had a chance to review this. Very on-board! Performed basic testing and did not spot any bugs or architectural concerns, but we all know how well code review works for that.
This needs a release note still before we merge it; although like always a stub is fine. The example description / title could probably be cleaned up too, but just try your best.
Once that's done this LGTM.
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Objective
Get clipping working with transformed nodes.
Fixes #17630
Fixes #21775
(and probably quite a few others)
Solution
CalculatedClipis now an enum withRectsandFullyClippedvariants.Rectsholds a list ofRectin node local coords andAffine2world-to-local transform.bevy_ui_renderhas a newclippingmodule with aclip_polygonfunction that intersects UI elements with the clipping rects and chops off the non-visible regions and returns a list of vertices that forms a triangle fan. Uses a simplified version of the Sutherland–Hodgman algorithm.Performance isn't too bad, but text suffers a bit when clipped as there's no broad phase atm, instead it tests and breaks up each glyph individually. The clipping geometry also needs to be cached somewhere and updated incrementally.
I didn't try to optimise this branch too much yet as I suspect the required changes would probably end up being much larger and more complicated than the clipping implementation itself, and it might better to leave them for follow up PRs.
Currently this only supports rectangular clipping regions but it can easily be expanded to support any covex shapes.
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Ideally we'd do clipping on the GPU which would allow for arbitrary clipping geometry and better performance. That would need a complete rewrite of the UI renderer and might have compatibility issues. I think this is good enough as an improving step, it works reliably and the code is also simpler and easier to understand, in particular UV interpolation is much simpler now.
Testing
Showcase