[Engine] Fast blurring algorithm for RSuperellipse #169187

dkwingsmt · 2025-05-21T05:54:36Z

This PR adds a fast blurring algorithm for RSuperellipses with uniform corner radius, similar to AttemptDrawBlurredRRect.

Fixes #163893. Fixes #167366.

This approximate algorithm is implemented by adding additional retraction to RRect's algorithm. Since they share most the logic, much effort is made to ensure reasonable code share.

I've also built a playground test RoundSuperellipseShadowComparison to compare the effect between the fast algorithm and the bruteforce algorithm, and added a macrobenchmark "rsuperellipse_blur".

Result

The following video shows the reproduction app from #167366, which shows much better framerate on RSE after the PR, almost the same as RRect. (I've verified that it was much worse without the PR.)

Screen.Recording.2025-05-20.at.11.59.38.PM.mp4

The following video shows the RoundSuperellipseShadowComparison playground, which compares the fast algorithm (left) against the bruteforce algorithm (right).

Pay attention to the cases with small but non zero sigma. They should be of almost the same shape as those with zero sigma, which skips the blurring altogether. With this algorithm, the difference between the two cases are about 1~2 pixel at most.

Screen.Recording.2025-05-21.at.12.57.02.AM.mp4

The following images compare macrobenchmarks "rrect_blur" against the new "rsuperellipse_blur". (Notice that the avg frame time fluctuates a lot but at least it shows that they're on par.)

Open questions

Should I improve the code share of shader files? Currently they're not shared mostly because I'm not sure about its gain and cost.

Pre-launch Checklist

I read the Contributor Guide and followed the process outlined there for submitting PRs.
I read the Tree Hygiene wiki page, which explains my responsibilities.
I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
I signed the CLA.
I listed at least one issue that this PR fixes in the description above.
I updated/added relevant documentation (doc comments with ///).
I added new tests to check the change I am making, or this PR is test-exempt.
I followed the breaking change policy and added Data Driven Fixes where supported.
All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

engine/src/flutter/impeller/entity/contents/solid_rrect_like_blur_contents.h

engine/src/flutter/impeller/entity/shaders/rsuperellipse_blur.frag

jonahwilliams · 2025-05-21T15:57:41Z

engine/src/flutter/impeller/entity/shaders/rsuperellipse_blur.frag

+  vec2 center;
+  vec2 adjust;
+  float minEdge;
+  float r1;
+  float exponent;
+  float sInv;
+  float exponentInv;
+  float scale;
+
+  float octantOffset;


RE: ordering. every uniform will take up a vec4 regardless of specified size. Since we have a lot of individual floats here, it will be better to pack them manually (similar to C structs, compilers won't do this automatically).

uniform FragInfo { vec4 abcd; } frag_info; float a = frag_info.a; float b = frag_info.b; ...

Do you mean that the RRect parameters (such as minEdge and r1) should be grouped like this as well?

You don't have to do all of them, but yeah - if you have a loooot floats (which this one does) it would be good to group them in the UBO.

engine/src/flutter/impeller/entity/shaders/rsuperellipse_blur.frag

engine/src/flutter/impeller/entity/shaders/rsuperellipse_blur.vert

jonahwilliams

Overall LGTM but I'd like to see the shader code tidied up a bit first.

engine/src/flutter/impeller/compiler/shader_lib/impeller/rrect.glsl

engine/src/flutter/impeller/display_list/canvas.h

jonahwilliams

LGTM

auto-submit · 2025-05-22T23:23:01Z

autosubmit label was removed for flutter/flutter/169187, because - The status or check suite Linux analyzer_benchmark has failed. Please fix the issues identified (or deflake) before re-applying this label.

jtmcdole · 2025-05-23T18:36:09Z

This has failed in the merge queue multiple times. The errors recently are:

../../../flutter/impeller/geometry/round_superellipse_param.cc:477:20: error: no matching function for call to 'ComputeQuadrant'
  477 |       .top_right = ComputeQuadrant(bounds.GetCenter(), bounds.GetRightTop(),
      |                    ^~~~~~~~~~~~~~~
../../../flutter/impeller/geometry/round_superellipse_param.cc:204:34: note: candidate function not viable: requires 4 arguments, but 3 were provided
  204 | RoundSuperellipseParam::Quadrant ComputeQuadrant(Point center,
      |                                  ^               ~~~~~~~~~~~~~
  205 |                                                  Point corner,
      |                                                  ~~~~~~~~~~~~~
  206 |                                                  Size in_radii,
      |                                                  ~~~~~~~~~~~~~~
  207 |                                                  Size sign) {

The merge group will rerun failures multiple times, which can block the queue for > 1 hour.

We should:

Figure out what is going on between presubmits and postsubmits
Revisit retrying in the merge group.

jonahwilliams · 2025-05-23T18:38:44Z

why is it building correctly in presubmit? maybe there are more changes stacked in master?

jtmcdole · 2025-05-23T18:39:52Z

why is it building correctly in presubmit? maybe there are more changes stacked in master?

Either stacked in master, or stacked under this pr in the queue. I'll look and see.

dkwingsmt · 2025-05-23T18:45:33Z

The error was right. A PR I merged last night caused this compilation error. I'll fix it.

#167977 changed the signature of ComputeQuadrant, and this PR called ComputeQuadrant in a new place. It was not caught in presubmit probably because its base commit was not updated.

dkwingsmt · 2025-05-23T18:52:41Z

I've fixed the error and verified that it builds and works when updated with the latest main. Sorry for the trouble.

jtmcdole · 2025-05-23T20:38:05Z

Thankyou @dkwingsmt!

…/flutter#169187)

flutter/flutter@85564cb...60050a0 2025-05-24 [email protected] Roll Skia from 0834eea9de33 to 91dc88dc70e5 (1 revision) (flutter/flutter#169414) 2025-05-24 [email protected] Roll Dart SDK from 0a6b16a55b9e to 7dab9bffe1f7 (1 revision) (flutter/flutter#169406) 2025-05-24 [email protected] Correct calculation for CupertinoTextSelectionToolbar vertical position (flutter/flutter#169308) 2025-05-24 [email protected] Baseline-align CupertinoTextField placeholder (flutter/flutter#166952) 2025-05-24 [email protected] Roll Dart SDK from 8354914ef97b to 0a6b16a55b9e (3 revisions) (flutter/flutter#169403) 2025-05-24 [email protected] Start removing Observatory support and references (flutter/flutter#169216) 2025-05-23 [email protected] Roll Skia from f42bb59753fe to 0834eea9de33 (3 revisions) (flutter/flutter#169393) 2025-05-23 [email protected] Roll Skia from 956fd8b14e22 to f42bb59753fe (2 revisions) (flutter/flutter#169379) 2025-05-23 [email protected] [Engine] Fast blurring algorithm for RSuperellipse (flutter/flutter#169187) 2025-05-23 [email protected] Add a page describing best CI practices for `flutter`-org repos (flutter/flutter#169364) 2025-05-23 [email protected] Revert "Mark web_tool_tests_1_2 as bringup." (flutter/flutter#169361) 2025-05-23 [email protected] Add changelog section for 3.32.0 and 3.32.1, and add note for ndk checking cherry pick (flutter/flutter#169369) 2025-05-23 [email protected] Roll Dart SDK from 085f110ecf33 to 8354914ef97b (1 revision) (flutter/flutter#169349) 2025-05-23 [email protected] Remove handling of the legacy `.flutter-plugins` file in `PluginHandler.kt`. (flutter/flutter#169317) 2025-05-23 [email protected] Use baseUri of WebAssetServer for reload_scripts.json (flutter/flutter#169267) 2025-05-23 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Use pub workspace (#168662)" (flutter/flutter#169357) 2025-05-23 [email protected] Use pub workspace (flutter/flutter#168662) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages Please CC [email protected],[email protected] on the revert to ensure that a human is aware of the problem. To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

This PR adds a fast blurring algorithm for `RSuperellipse`s with uniform corner radius, similar to `AttemptDrawBlurredRRect`. Fixes flutter#163893. Fixes flutter#167366. This approximate algorithm is implemented by adding additional retraction to RRect's algorithm. Since they share most the logic, much effort is made to ensure reasonable code share. I've also built a playground test `RoundSuperellipseShadowComparison` to compare the effect between the fast algorithm and the bruteforce algorithm, and added a macrobenchmark "rsuperellipse_blur". ### Result The following video shows the reproduction app from flutter#167366, which shows much better framerate on RSE after the PR, almost the same as RRect. (I've verified that it was much worse without the PR.) https://github.com/user-attachments/assets/5433af91-c0a1-4b15-9161-cf2280543e27 The following video shows the `RoundSuperellipseShadowComparison` playground, which compares the fast algorithm (left) against the bruteforce algorithm (right). * Pay attention to the cases with small but non zero sigma. They should be of almost the same shape as those with zero sigma, which skips the blurring altogether. With this algorithm, the difference between the two cases are about 1~2 pixel at most. https://github.com/user-attachments/assets/e26d2d8f-d29e-4db8-9c20-67103d77891c The following images compare macrobenchmarks "rrect_blur" against the new "rsuperellipse_blur". (Notice that the avg frame time fluctuates a lot but at least it shows that they're on par.) <img width="389" alt="image" src="https://github.com/user-attachments/assets/67cf4b10-f13f-4e55-bdfd-35d358617f38" /> <img width="365" alt="image" src="https://github.com/user-attachments/assets/6869fa9c-5752-4a11-babe-b6a2d590ebc9" /> ### Open questions * Should I improve the code share of shader files? Currently they're not shared mostly because I'm not sure about its gain and cost. ## Pre-launch Checklist - [ ] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [ ] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [ ] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [ ] I signed the [CLA]. - [ ] I listed at least one issue that this PR fixes in the description above. - [ ] I updated/added relevant documentation (doc comments with `///`). - [ ] I added new tests to check the change I am making, or this PR is [test-exempt]. - [ ] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [ ] All existing and new tests are passing. If you need help, consider asking for advice on the #hackers-new channel on [Discord].  [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

* master: (125 commits) Roll Fuchsia Linux SDK from XtPp9bBW49iDJ0wbA... to -eo2JqnJBauuGSzoW... (flutter#169424) Roll Skia from 91dc88dc70e5 to 443f5257f382 (1 revision) (flutter#169422) Roll Skia from 0834eea9de33 to 91dc88dc70e5 (1 revision) (flutter#169414) Roll Dart SDK from 0a6b16a55b9e to 7dab9bffe1f7 (1 revision) (flutter#169406) Correct calculation for CupertinoTextSelectionToolbar vertical position (flutter#169308) Baseline-align CupertinoTextField placeholder (flutter#166952) Roll Dart SDK from 8354914ef97b to 0a6b16a55b9e (3 revisions) (flutter#169403) Start removing Observatory support and references (flutter#169216) Roll Skia from f42bb59753fe to 0834eea9de33 (3 revisions) (flutter#169393) Roll Skia from 956fd8b14e22 to f42bb59753fe (2 revisions) (flutter#169379) [Engine] Fast blurring algorithm for RSuperellipse (flutter#169187) Add a page describing best CI practices for `flutter`-org repos (flutter#169364) Revert "Mark web_tool_tests_1_2 as bringup." (flutter#169361) Add changelog section for 3.32.0 and 3.32.1, and add note for ndk checking cherry pick (flutter#169369) Roll Dart SDK from 085f110ecf33 to 8354914ef97b (1 revision) (flutter#169349) Remove handling of the legacy `.flutter-plugins` file in `PluginHandler.kt`. (flutter#169317) Use baseUri of WebAssetServer for reload_scripts.json (flutter#169267) Reverts "Use pub workspace (flutter#168662)" (flutter#169357) Use pub workspace (flutter#168662) Reverts "[Reland2] Implements UISceneDelegate dynamically w/ FlutterLaunchEngine (flutter#169276)" (flutter#169347) ...

…r#9318) flutter/flutter@85564cb...60050a0 2025-05-24 [email protected] Roll Skia from 0834eea9de33 to 91dc88dc70e5 (1 revision) (flutter/flutter#169414) 2025-05-24 [email protected] Roll Dart SDK from 0a6b16a55b9e to 7dab9bffe1f7 (1 revision) (flutter/flutter#169406) 2025-05-24 [email protected] Correct calculation for CupertinoTextSelectionToolbar vertical position (flutter/flutter#169308) 2025-05-24 [email protected] Baseline-align CupertinoTextField placeholder (flutter/flutter#166952) 2025-05-24 [email protected] Roll Dart SDK from 8354914ef97b to 0a6b16a55b9e (3 revisions) (flutter/flutter#169403) 2025-05-24 [email protected] Start removing Observatory support and references (flutter/flutter#169216) 2025-05-23 [email protected] Roll Skia from f42bb59753fe to 0834eea9de33 (3 revisions) (flutter/flutter#169393) 2025-05-23 [email protected] Roll Skia from 956fd8b14e22 to f42bb59753fe (2 revisions) (flutter/flutter#169379) 2025-05-23 [email protected] [Engine] Fast blurring algorithm for RSuperellipse (flutter/flutter#169187) 2025-05-23 [email protected] Add a page describing best CI practices for `flutter`-org repos (flutter/flutter#169364) 2025-05-23 [email protected] Revert "Mark web_tool_tests_1_2 as bringup." (flutter/flutter#169361) 2025-05-23 [email protected] Add changelog section for 3.32.0 and 3.32.1, and add note for ndk checking cherry pick (flutter/flutter#169369) 2025-05-23 [email protected] Roll Dart SDK from 085f110ecf33 to 8354914ef97b (1 revision) (flutter/flutter#169349) 2025-05-23 [email protected] Remove handling of the legacy `.flutter-plugins` file in `PluginHandler.kt`. (flutter/flutter#169317) 2025-05-23 [email protected] Use baseUri of WebAssetServer for reload_scripts.json (flutter/flutter#169267) 2025-05-23 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Use pub workspace (#168662)" (flutter/flutter#169357) 2025-05-23 [email protected] Use pub workspace (flutter/flutter#168662) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages Please CC [email protected],[email protected] on the revert to ensure that a human is aware of the problem. To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

…/flutter#169187)

Rebase

e3219f8

github-actions bot added engine flutter/engine related. See also e: labels. e: impeller Impeller rendering backend issues and features requests labels May 21, 2025

dkwingsmt added 3 commits May 21, 2025 00:06

Licence

a4211e3

Move v out

ff7d20e

Move nInvNeg out

00466f7

dkwingsmt marked this pull request as ready for review May 21, 2025 08:03

dkwingsmt requested a review from jonahwilliams May 21, 2025 08:03

jonahwilliams reviewed May 21, 2025

View reviewed changes

dkwingsmt added 4 commits May 21, 2025 22:20

Comment

f39aba3

Extract rrect.glsl

77f1720

Fix compile

6ff0940

Move VS out

2785adc

jonahwilliams reviewed May 22, 2025

View reviewed changes

engine/src/flutter/impeller/compiler/shader_lib/impeller/rrect.glsl Show resolved Hide resolved

jonahwilliams reviewed May 22, 2025

View reviewed changes

engine/src/flutter/impeller/display_list/canvas.h Outdated Show resolved Hide resolved

jonahwilliams approved these changes May 22, 2025

View reviewed changes

dkwingsmt added 5 commits May 22, 2025 13:24

Trivial comments

19ff427

Group numbers

8882037

Remove axesDiff

d41579e

Better doc

c750ee8

macrobenchmark

14667fd

dkwingsmt added the autosubmit Merge PR when tree becomes green via auto submit App label May 22, 2025

auto-submit bot removed the autosubmit Merge PR when tree becomes green via auto submit App label May 22, 2025

dkwingsmt added 4 commits May 22, 2025 17:59

analyze

b4fe93c

license

d339bcb

Format

9bac449

malioc

68baf75

dkwingsmt added the autosubmit Merge PR when tree becomes green via auto submit App label May 23, 2025

jtmcdole mentioned this pull request May 23, 2025

Revisit: Retrying in the merge group #169377

Open

dkwingsmt added 2 commits May 23, 2025 11:45

Merge remote-tracking branch 'origin/main' into rse-fast-shadow

4664608

Fix compile

7600c9b

matanlurey approved these changes May 23, 2025

View reviewed changes

dkwingsmt added the autosubmit Merge PR when tree becomes green via auto submit App label May 23, 2025

auto-submit bot added this pull request to the merge queue May 23, 2025

Merged via the queue into flutter:master with commit ea1c1ba May 23, 2025
181 checks passed

flutter-dashboard bot removed the autosubmit Merge PR when tree becomes green via auto submit App label May 23, 2025

dkwingsmt deleted the rse-fast-shadow branch May 23, 2025 21:32

Piinks mentioned this pull request May 23, 2025

Flutter Notable Commits - 2025 #161460

Open

jtmcdole added a commit to jtmcdole/cocoon that referenced this pull request May 23, 2025

DO_NOT_SUBMIT: test data for flutter/flutter#169187

f3f549d

engine-flutter-autoroll mentioned this pull request May 24, 2025

Roll Flutter from 85564cbba9e7 to 60050a0b4d56 (17 revisions) flutter/packages#9318

Merged

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request May 24, 2025

ea1c1bae8 [Engine] Fast blurring algorithm for RSuperellipse (flutter…

6467b1c

…/flutter#169187)

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 14, 2025

ea1c1bae8 [Engine] Fast blurring algorithm for RSuperellipse (flutter…

4ac6107

…/flutter#169187)

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 14, 2025

ea1c1bae8 [Engine] Fast blurring algorithm for RSuperellipse (flutter…

c3bbf30

…/flutter#169187)

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 15, 2025

ea1c1bae8 [Engine] Fast blurring algorithm for RSuperellipse (flutter…

fad3841

…/flutter#169187)

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 15, 2025

ea1c1bae8 [Engine] Fast blurring algorithm for RSuperellipse (flutter…

65df1c2

…/flutter#169187)

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 16, 2025

ea1c1bae8 [Engine] Fast blurring algorithm for RSuperellipse (flutter…

3a70a50

…/flutter#169187)

[Engine] Fast blurring algorithm for RSuperellipse #169187

[Engine] Fast blurring algorithm for RSuperellipse #169187

Uh oh!

Conversation

dkwingsmt commented May 21, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Result

Open questions

Pre-launch Checklist

Uh oh!

Uh oh!

Uh oh!

jonahwilliams May 21, 2025

Choose a reason for hiding this comment

Uh oh!

dkwingsmt May 22, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

jonahwilliams May 22, 2025

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

jonahwilliams left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

jonahwilliams left a comment

Choose a reason for hiding this comment

Uh oh!

auto-submit bot commented May 22, 2025

Uh oh!

jtmcdole commented May 23, 2025

Uh oh!

jonahwilliams commented May 23, 2025

Uh oh!

jtmcdole commented May 23, 2025

Uh oh!

dkwingsmt commented May 23, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

dkwingsmt commented May 23, 2025

Uh oh!

jtmcdole commented May 23, 2025

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

dkwingsmt commented May 21, 2025 •

edited

Loading

dkwingsmt May 22, 2025 •

edited

Loading

dkwingsmt commented May 23, 2025 •

edited

Loading