1691139 - Use cheaper approximations for WR shader anti-aliasing

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, enhancement)

Description

[Lee Salzman [:lsalzman]]

The signed-distance and coverage area approximations we use for shader anti-aliasing in WR are expensive due to usage of branching and normalization. There are cheaper approximations we can use that give perceptibly similar results so long as we're willing to take the hit in reftest fuzz.

Comment 1

[Lee Salzman [:lsalzman]]

Attachment: Bug 1691139 - Use cheaper linear approximation for WR shader anti-aliasing. r?jrmuizel,gw

Comment 2

[Lee Salzman [:lsalzman]]

Attachment: Bug 1691139 - Update wrench png refs for revised WR shader anti-aliasing. r?jrmuizel,gw

Depends on D104270

Comment 3

[Lee Salzman [:lsalzman]]

Attachment: Bug 1691139 - Optimize init_transform_fs for SWGL fast-paths where there is no perspective. r?jrmuizel

The result of compute_aa_range depends on fwidth(local_pos). In the no-perspective case,
the derivatives of local_pos are constant across an entire primitive. SWGL fast-paths only
run in the no-perspective case anyway, so it is convenient to compute the aa_range once
for the entire span and then reuse it, factoring out this per-pixel cost.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/8d1fc04130de
Use cheaper linear approximation for WR shader anti-aliasing. r=gw
https://hg.mozilla.org/integration/autoland/rev/0f12cc02b12e
Update wrench png refs for revised WR shader anti-aliasing. r=gw
https://hg.mozilla.org/integration/autoland/rev/f4f3f317a7d6
Optimize init_transform_fs for SWGL fast-paths where there is no perspective. r=jrmuizel

Comment 5

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/8d1fc04130de
https://hg.mozilla.org/mozilla-central/rev/0f12cc02b12e
https://hg.mozilla.org/mozilla-central/rev/f4f3f317a7d6

Comment 6

[Alexandru Ionescu (needinfo me) [:alexandrui]]

== Change summary for alert #28694 (as of Tue, 09 Feb 2021 12:56:20 GMT) ==

Improvements:

Ratio	Suite	Test	Platform	Options	Absolute values (old vs new)
3%	tart		linux64-shippable-qr	e10s stylo webrender-sw	3.47 -> 3.37

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=28694

Comment 7

[Florin Strugariu [:Bebe]]

== Change summary for alert #28736 (as of Thu, 11 Feb 2021 07:55:31 GMT) ==

Improvements:

Ratio	Suite	Test	Platform	Options	Absolute values (old vs new)
6%	raptor-tp6-sheets-firefox-cold	fcp	windows10-64-shippable-qr	nocondprof webrender	693.17 -> 650.75
5%	raptor-tp6-sheets-firefox-cold	fcp	windows10-64-shippable-qr	nocondprof webrender	684.58 -> 647.50

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=28736