965848 - implement EXT_shader_texture_lod-like extension for WebGL

Status: RESOLVED FIXED

(Core :: Graphics: CanvasWebGL, defect)

Description

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Attachment: EXT_shader_texture_lod, v0

This was identified as a large contributor to visual quality by some of our partners.  On mobile, it's available on PowerVR and Mali, but not on Adreno and Tegra.  EXT_shader_texture_lod is standard available on iOS (and on the desktop), so in many cases it's an issue where the desktop should be able to look at least as good as iOS.

Note also that it's core required in ES3, and Adreno/Tegra have ES3 drivers, so I'm not sure why they also don't expose the extension.

However, we can't take EXT_shader_texture_lod as-is, because it also includes a bunch of Grad functions that are exposed to both vertex and fragment shaders.  In D3D, these are only available in pixel shaders.  They can be emulated by writing some math in the vertex shader though, and I'm tempted to do that.. but it also might get complex to get the interaction between lod/bias/etc. right.

The attached prototype patch implements "EXT_shader_texture_lod", but only the Lod portions.  I'll likely rename this MOZ_shader_texture_lod_limited or something.  But, I would like to land this very soon under a default-off pref.  Thoughts?

Comment 1

[Benoit Jacob [:bjacob] (mostly away)]

Comment on attachment 8367994 [details] [diff] [review]
EXT_shader_texture_lod, v0

Review of attachment 8367994 [details] [diff] [review]:
-----------------------------------------------------------------

I can't see anything wrong with that, at least at the "feedback" stage. I have no idea about the D3D aspects though. If there were a showstopper there, I would be missing it.

Just one thing: if this is important enough to get implemented behind a pref, it's probably important enough to write a spec for, and get the proposal/draft process going.

Comment 2

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Yeah, absolutely; I plan on writing that up as well.

Comment 3

[Kelsey Gilbert [:jgilbert]]

Comment on attachment 8367994 [details] [diff] [review]
EXT_shader_texture_lod, v0

Review of attachment 8367994 [details] [diff] [review]:
-----------------------------------------------------------------

Cool, but yeah, let's get a spec together.

Comment 4

[Florian Bösch]

EXT_shader_texture_lod extension specification has been moved to draft: http://www.khronos.org/registry/webgl/extensions/EXT_shader_texture_lod/

Comment 5

[Florian Bösch]

Chrome ticket: https://code.google.com/p/chromium/issues/detail?id=344583

Webkit ticket: https://bugs.webkit.org/show_bug.cgi?id=128985

Angle ticket: https://code.google.com/p/angleproject/issues/detail?id=551

Comment 6

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

This is now in upstream ANGLE as of ~3 weeks ago.  Can we take an ANGLE update so we can get this in for 32?

Comment 7

[Alex Christensen]

I had to modify the test case to get it to run properly on WebKit.  I imagine the same should be done here.  It was a simple fix:

-var gl = create3DContext(canvas);
+var gl = wtu.create3DContext(canvas);

Comment 8

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Attachment: EXT_shader_texture_lod, v1

Updated now that we have new ANGLE.

Comment 9

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

So I was about to land this, but the test itself is timing out https://tbpl.mozilla.org/?tree=Try&rev=80d9bba82e28 in a way that I don't understand.  It's as if it's not even running.  The test worked last time I tried it, but windows builds with tests are a little broken right now for me for some reason (bug 1043128).

Comment 10

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Attachment: updated patch with missing test file exported

So all it was was just a missing export of the test file.

https://tbpl.mozilla.org/?tree=Try&rev=04d124cbcac6

(The linux debug failures cannot be related)

Comment 11

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 8453925 [details] [diff] [review]
EXT_shader_texture_lod, v1

r=me on the webidl change

Comment 12

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

https://hg.mozilla.org/integration/mozilla-inbound/rev/c2c9caaa8fdd

Comment 13

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/c2c9caaa8fdd

Comment 14

[Florian Bösch]

Extension does not show up on OSX. Chrome has it (86%), Safari (96%) and Opera (96%). I suggest this is not fixed.

Comment 15

[Cedric Pinson]

yep does not work on osx / linux