Texture sampling problems - DX9 and GL backends do not produce identical output

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Download the attached file and run it in Chrome with GL and DX9 
implementations
2. Compare visual output

What is the expected output? What do you see instead?
OpenGL implementation produces the expected output with nice, readable font 
characters, even for the fine text. DX9 implementation does not.

Screnshots in the zip package illustrate what it looks like on my machine. 
"font-test-opengl.png" contains the expected output.

What version of the product are you using? On what operating system?
Using latest Chrome for Windows 7 at time of posting

Please provide any additional information below.
Note that the attached test case implements Signed Distance Field font 
rendering, which exaggerates the problem visually. *The problem does however 
ALSO occur in the possible simplest case, where a pixel is sampled and returned 
directly 1:1 texel per pixel in the pixel shader, as long as texture filtering 
is enabled (but is not that easy to spot)*

Original issue reported on code.google.com by Ducker...@gmail.com on 26 Nov 2012 at 2:19

Attachments:

• texturing-on-dx-issue.rar

[GoogleCodeExporter]

Thanks for the test case. Unfortunately, the small text looks poor on both 
Chrome's ANGLE and OpenGL backends on my Windows 7 machine with NVIDIA Quadro 
FX 380. Running Chrome 25.0.1335.0 (Official Build 169404) canary.

Daniel, Nicolas, can you see a difference in behavior on your machines? I 
tested both backends by running

C:\Users\[username]\AppData\Local\Google\Chrome SxS\Application\chrome.exe

with and without --use-gl=desktop (and confirmed in about:gpu that the 
--use-gl=desktop flag was taking effect).

Original comment by kbr@chromium.org on 26 Nov 2012 at 7:24

[GoogleCodeExporter]

It might look poor, but do they look poor in the same way? I.e. are they 
identical?

Original comment by Ducker...@gmail.com on 26 Nov 2012 at 7:27

[GoogleCodeExporter]

Yes, they look identical. Attached for comparison.

Perhaps this is related to centroid multisampling?

What is the output of about:gpu on your machine?

Original comment by kbr@chromium.org on 26 Nov 2012 at 8:52

Attachments:

• angle.png
• opengl.png

[GoogleCodeExporter]

I had to use the --disable-web-security flag to be able to run the test sample.

I'm getting the same results as Ken; the small white text is very badly 
readable, both with ANGLE and desktop OpenGL. This is on Canary 25.0.1337.0 
with an Intel HD Graphics 2000. I've also tested with an ATI FirePro V5700 and 
got the same bad rendering with ANGLE, while with desktop OpenGL nothing was 
rendered at all.

Original comment by nicolas....@gmail.com on 28 Nov 2012 at 8:31

[GoogleCodeExporter]

Original comment by c...@chromium.org on 7 Dec 2013 at 4:06

[GoogleCodeExporter]

Original comment by geofflang@chromium.org on 10 Dec 2013 at 3:53