1687977 - Render radial and conic gradients as cached images

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, enhancement, P3)

Description

[Nicolas Silva [:nical]]

Currently gradients are rendered:

• conic or radial gradients: as a brush in the main pass
• linear: under some conditions they are pre-rendered in a cached render task and composited with the image brush shader (fast path), otherwise rendered directly using the linear gradient brush shader. The conditions are:
  • The gradient covers the entire primitive
  • It must be vertical or horizontal
  • it must not have segments

The goal is for all gradients to be pre-rendered as a cached render task in all situation. The motivations for this are:

• performance: it is faster to cache the rendered gradients once and composite a simple image every frame, than to run the gradient shaders every frame, in particular for swgl
• simplify the rendering code by reducing the number of brush shader types. (Ideally we want to converge towards having only image and solid brushes in the main pass).

Comment 1

[Nicolas Silva [:nical]]

Potential solution:

Render in 3 steps:

• 1: Render the gradient stops (whatever the type) as a horizontal line in a first pass, so that the second pass doesn't have to deal with gradient stops.
• 2: in a second pass, a gradient shader samples this line to generate the image (a shader per gradient type: linear/radial/conic)
• 3: the image brush shader is used to composite the image in the main pass.

If the gradient is linear and axis aligned, we can skip step 2 (today's fast path) and stretch the gradient line from step 1 direcly when compositing.

I'm not sure how hard we need hard gradient stops to be: If there is a hard stop, is it ok to render it in step 1 and that step 2 potentially samples in between (that would creat a sort of anti-aliased transition at the hard stop)? If this is not OK, then we have to combine step 1 and 2 and have the gradient shaders deal with hard stops. The advantage of not doing that is that we can avoid requiring a variable amount of inputs in the cached render tasks even with many gradient stops: each transition between two colors can be rendered with a separate quad.

I don't see a particular reason why this would not work with segmented primitives. I suspect that the linear gradient fast path currently does not support them to avoid duplicating code but that needs to be refactored.

Comment 2

[Nicolas Silva [:nical]]

Attachment: Bug 1687977 - Part 1 - Rename cs_gradient into cs_fast_linear_gradient. r=gw

It is the cs_* shader used to cache linear gradients in the simple/fast path (more complex linear gradients are rendered with a brush shader. The goal of this patch series is to move all gradients to cached render tasks that will be composited with brush_image, so there will be a cs_linear_gradient introduced in a followup to cover the general case as well as cs_radial_gradient and cs_conic_gradient to replace the brush equivalents.

Comment 3

[Nicolas Silva [:nical]]

Attachment: Bug 1687977 - Part 2 - Split prim_store/gradient.rs into sub-modules. r=gw

prim_store/gradient.rs is large enough that splitting it up will make things a bit clearer. The new organization is:

• prim_store/gradient/mod.rs: shared/gradient-agnostic code.
• prim_store/gradient/<linear|radial|conic>.rs: specific gradient code.

In addition, various gradient-specific data structures currently living in other modules will move into the proper gradient modules as part of this patch series.

For convenience, all specific public symbols are reexported in prim_store::gradient.

Depends on D107640

Comment 4

[Nicolas Silva [:nical]]

Attachment: Bug 1687977 - Part 3 - rename gradient into fast_linear_gradient in various places. r=gw

Historically WebRender's code has used 'gradient' as a shorthand for 'linear gradient' and often more specifically for 'the fast path for linear gradients'. This patch makes the naming less ambiguous in particular in places where we'll see more types of gradients sid by side introduced by upcoming patches in this series.

Depends on D107641

Comment 5

[Nicolas Silva [:nical]]

Attachment: Bug 1687977 - Part 4 - Move FastLinearGradientTask into gradient/linear.rs

In the spirit of keeping primitive-specific logic mostly in the same place, this moves the linear gradient render task and the code to convert it into a gpu-visible instance into linear.rs.

I'm planning to give all specific render task structures/logic the same treatment eventually.

Depends on D107642

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/9f140075b49f
Part 1 - Rename cs_gradient into cs_fast_linear_gradient. r=gw
https://hg.mozilla.org/integration/autoland/rev/e5e58b10664a
Part 2 - Split prim_store/gradient.rs into sub-modules. r=gw
https://hg.mozilla.org/integration/autoland/rev/0b2d5a01cba8
Part 3 - rename gradient into fast_linear_gradient in various places. r=gw
https://hg.mozilla.org/integration/autoland/rev/ac798a0fe9e0
Part 4 - Move FastLinearGradientTask into gradient/linear.rs r=gw

Comment 7

[Dorel Luca [:dluca]]

https://hg.mozilla.org/mozilla-central/rev/9f140075b49f
https://hg.mozilla.org/mozilla-central/rev/e5e58b10664a
https://hg.mozilla.org/mozilla-central/rev/0b2d5a01cba8
https://hg.mozilla.org/mozilla-central/rev/ac798a0fe9e0

Comment 8

[Nicolas Silva [:nical]]

Attachment: Bug 1687977 - Part 5 - More Gradient/FastLienarGradient renaming. r=gw

Comment 9

[Nicolas Silva [:nical]]

Attachment: Bug 1687977 - Part 6 - Split gradient_shared.glsl. r=gw

The parts stay in gradient_shared.glsl are specific to the gradient brushes, dont build without outside of the brsuh infrastructure and will be removed along with the brush gradients. The parts that go into gradient.glsl will be shared between the different gradient render task shaders.

Depends on D108464

Comment 10

[Nicolas Silva [:nical]]

Attachment: Bug 1687977 - Part 7 - Render radial gradients using render tasks. r=gw

There was a lot of trial and error in the process of making this patch, so unfortunately I didn't manage to plan it out in smaller independent steps.

This patch introduces a new cs_radial_gradient shader to use instead of the brush radial gradient shader. The gradient is produced by a cached render task and composited via the image brush.

As a bonus, tiled radial gradients now get a chance to be in the opaque pass (the previous logic was overly conservative).

Depends on D108465

Comment 11

[Nicolas Silva [:nical]]

Attachment: Bug 1687977 - Part 8 - Remove brush_radial_gradient. r=gw

Depends on D108467

Comment 12

[Nicolas Silva [:nical]]

Attachment: Bug 1687977 - Part 9 - Gracefully handle huge radial gradients. r=gw

Depends on D108468

Comment 13

[Nicolas Silva [:nical]]

Attachment: Bug 1687977 - Part 11 - Adjust reftest references. r=gw

Depends on D108469

Comment 14

[Nicolas Silva [:nical]]

Attachment: Bug 1687977 - Part 12 - Render conic gradients using render tasks. r=gw

Depends on D108470

Comment 15

[Nicolas Silva [:nical]]

Attachment: Bug 1687977 - Part 10 - Optimize large radial gradients. r=gw

Depends on D108606

Comment 16

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/3842ded5b2c1
Part 5 - More Gradient/FastLienarGradient renaming. r=gw
https://hg.mozilla.org/integration/autoland/rev/9200289b567e
Part 6 - Split gradient_shared.glsl. r=gw

Comment 17

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/3842ded5b2c1
https://hg.mozilla.org/mozilla-central/rev/9200289b567e

Comment 18

[Nicolas Silva [:nical]]

Attachment: Bug 1687977 - Part 13 - Remove brush_conic_gradient. r=gw"

Depends on D108606

Comment 19

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/2865e8332baa
Part 7 - Render radial gradients using render tasks. r=gw
https://hg.mozilla.org/integration/autoland/rev/2f392cb56f71
Part 8 - Remove brush_radial_gradient. r=gw
https://hg.mozilla.org/integration/autoland/rev/526d512c6cf9
Part 9 - Gracefully handle huge radial gradients. r=gw
https://hg.mozilla.org/integration/autoland/rev/ddceb031f73b
Part 10 - Optimize large radial gradients. r=jrmuizel,gw
https://hg.mozilla.org/integration/autoland/rev/72bcd469b597
Part 11 - Adjust reftest references. r=gw
https://hg.mozilla.org/integration/autoland/rev/56ef057fc29c
Part 12 - Render conic gradients using render tasks. r=gw
https://hg.mozilla.org/integration/autoland/rev/47f20111056a
Part 13 - Remove brush_conic_gradient. r=gw"

Comment 20

[Noemi Erli[:noemi_erli]]

Backed out 7 changesets (Bug 1687977) for causing build bustages CLOSED TREE

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&group_state=expanded&collapsedPushes=842382&selectedTaskRun=IMuXFOLDTdeCSrSlLu8Rzg.0&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&revision=47f20111056a1da9f8776b6aab903e8594fd1c88

Failure log: https://treeherder.mozilla.org/logviewer?job_id=333755206&repo=autoland&lineNumber=13235
https://treeherder.mozilla.org/logviewer?job_id=333755187&repo=autoland&lineNumber=56987

Backout: https://hg.mozilla.org/integration/autoland/rev/80fb40ff105a6fb937bf48ec17d65b0d449f0a8b

Comment 21

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/bc70dc8ad3a7
Part 7 - Render radial gradients using render tasks. r=gw
https://hg.mozilla.org/integration/autoland/rev/b88325347b88
Part 8 - Remove brush_radial_gradient. r=gw
https://hg.mozilla.org/integration/autoland/rev/0d96a981a333
Part 9 - Gracefully handle huge radial gradients. r=gw
https://hg.mozilla.org/integration/autoland/rev/ca611e922f49
Part 10 - Optimize large radial gradients. r=jrmuizel,gw
https://hg.mozilla.org/integration/autoland/rev/cd256e69c920
Part 11 - Adjust reftest references. r=gw
https://hg.mozilla.org/integration/autoland/rev/edd376ea0b95
Part 12 - Render conic gradients using render tasks. r=gw
https://hg.mozilla.org/integration/autoland/rev/4575418fa949
Part 13 - Remove brush_conic_gradient. r=gw"

Comment 22

[Cristian Brindusan [:cbrindusan]]

https://hg.mozilla.org/mozilla-central/rev/bc70dc8ad3a7
https://hg.mozilla.org/mozilla-central/rev/b88325347b88
https://hg.mozilla.org/mozilla-central/rev/0d96a981a333
https://hg.mozilla.org/mozilla-central/rev/ca611e922f49
https://hg.mozilla.org/mozilla-central/rev/cd256e69c920
https://hg.mozilla.org/mozilla-central/rev/edd376ea0b95
https://hg.mozilla.org/mozilla-central/rev/4575418fa949

Comment 23

[Florin Strugariu [:Bebe]]

== Change summary for alert #29391 (as of Tue, 23 Mar 2021 08:08:58 GMT) ==

Improvements:

Ratio	Suite	Test	Platform	Options	Absolute values (old vs new)
7%	microsoft	PerceptualSpeedIndex	windows10-64-shippable-qr	cold nocondprof webrender	605.46 -> 562.33
6%	microsoft	FirstVisualChange	windows10-64-shippable-qr	cold nocondprof webrender	597.83 -> 564.92
5%	microsoft	SpeedIndex	windows10-64-shippable-qr	cold nocondprof webrender	599.29 -> 566.92
5%	microsoft	ContentfulSpeedIndex	windows10-64-shippable-qr	cold nocondprof webrender	601.29 -> 569.58
5%	microsoft	PerceptualSpeedIndex	windows10-64-shippable-qr	cold nocondprof webrender	601.12 -> 569.58
5%	reddit	loadtime	linux1804-64-shippable-qr	nocondprof warm webrender	2,171.25 -> 2,071.21
3%	wikipedia	fcp	linux1804-64-shippable	cold nocondprof	1,637.44 -> 1,586.42

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=29391

Comment 25

[Henrik Skupin [:whimboo][⌚️UTC+2] (away 07/21 - 08/08)]

Nicolas, is more work needed on this bug or can it be closed now?

Comment 26

[Nicolas Silva [:nical]]

I did conic and radial gradients, there's still linear gradients but it's more complicated (surprisingly) and I'm focusing on other things right now. I'll change the bug title so that we can close this one.