[Public WebGL] Problem with 'more-than-65536-points.html' test

Kenneth Russell [email protected]
Tue Sep 27 10:10:24 PDT 2011


This sounds like a driver bug; multisampling should not cause cracks to
appear between adjacent triangles. However, I agree with you that the test
should focus specifically on rendering a large number of triangles. I've
committed an update which disables antialiasing for this test, since it was
a much larger refactoring to turn it into a reference test.

-Ken

On Mon, Sep 26, 2011 at 7:51 PM, Jeff Gilbert <[email protected]> wrote:

> It also appears to exhibit the same behavior on linux.
> It may very well be an issue with the nVidia drivers for my GPU, but my
> point about the aim of the test stands.
>
> -Jeff
>
> ----- Original Message -----
> From: "Jeff Gilbert" <[email protected]>
> To: "Gregg Tavares (wrk)" <[email protected]>
> Cc: "Kenneth Russell" <[email protected]>, "public webgl" <
> [email protected]>
> Sent: Monday, September 26, 2011 6:19:37 PM
> Subject: Re: [Public WebGL] Problem with 'more-than-65536-points.html' test
>
>
> "I don't see how this test would have anything to do with anti-aliasing. "
> Exactly. It is confusing that this test should fail because of
> anti-aliasing. Right now, I am getting false-positives, where the test is
> failing, but what is being tested by the test is working properly.
>
> The issue lies in that it doesn't draw actual quads; it draws pairs of
> tris, which should be the same thing as quads. However, this is evidently
> not the case on one of my rendering paths, at least with 2xAA. (0x and 8x
> work fine)
>
> Regardless, this is a problem that seems to only occur for some sampling
> patterns. Making the test single-sampled will make it more reliable by
> further minimizing false-positive errors.
>
> Really what this test should do is first run using only 2 quads (one red,
> second one green), then run using 65536 / 6 + 2 quads (n-1 red, last one
> green), and compare the results. If the buffers are the same, then there is
> no bug in drawing large numbers of points, whether or not there are other
> problems with rendering.
>
> To clarify, the buffer I'm seeing on affected paths is green, with the
> exception of a faint red line along part of the seam between the two tris.
> (seam is bottom-left to top-right)
>
> -Jeff
>
> ----- Original Message -----
> From: "Gregg Tavares (wrk)" <[email protected]>
> To: "Jeff Gilbert" <[email protected]>
> Cc: "Kenneth Russell" <[email protected]>, "public webgl" <
> [email protected]>
> Sent: Monday, September 26, 2011 5:47:14 PM
> Subject: Re: [Public WebGL] Problem with 'more-than-65536-points.html' test
>
> I don't see how this test would have anything to do with anti-aliasing.
>
>
> It just draws overlapping quads. It draws overlapping quads, all at the
> same location, the only difference being the last quad is a green instead of
> red.
>
>
> All the test does is check the last quad gets drawn by checking for green
>
>
> (in other words, if there was a bug that limited count to 65535 then the
> last quad would not be drawn and you'd see red)
>
>
>
>
>
>
>
>
>
> On Mon, Sep 26, 2011 at 4:38 PM, Jeff Gilbert < [email protected] >
> wrote:
>
>
>
> Yes, it's bleed-through from between the two tris, a line of faint reddish
> pixels along part of the seam. This is the only test which is regressing
> from without antialiasing.
> There's clearly a problem somewhere, but it isn't a problem with the number
> of points: When I reduce the number of quads to only two (one red, then one
> green), the problem persists.
>
> If we want to test for bleed-through with AA, we should absolutely do so,
> but (if possible) not in an unrelated test. I'm willing to write up a test
> if we want to add this.
>
> I agree that it's odd that this is the only test where this is apparently a
> problem, however I would like to be sure that when this test fails, that
> it's not just because of antialiasing issues, and is instead because of
> improper handling of large numbers of points.
>
> -Jeff
>
>
>
>
>
> ----- Original Message -----
> From: "Kenneth Russell" < [email protected] >
> To: "Jeff Gilbert" < [email protected] >
> Cc: "public webgl" < [email protected] >
> Sent: Monday, September 26, 2011 4:12:24 PM
> Subject: Re: [Public WebGL] Problem with 'more-than-65536-points.html' test
>
> How exactly is the test failing? Are non-green pixels bleeding through
> at the edges of the canvas, or is something else happening?
>
> I don't think we've seen any failures of this test on any platform in
> Chromium, where antialiasing support for WebGL has been present for
> some time.
>
> It's strange that only this test would be affected by the presence of
> antialiasing. Are you sure that others aren't affected?
>
> In principle it would be fine with me to disable antialiasing for this
> test, but I feel that would probably be a hack which doesn't really
> solve the problem.
>
> -Ken
>
> On Mon, Sep 26, 2011 at 3:04 PM, Jeff Gilbert < [email protected] >
> wrote:
> >
> > Hi,
> >
> > In implementing antialiasing for Firefox, I am getting failures on this
> test for some rendering paths, and only for some sampling levels.
> > While it's possible that this is a driver bug (since this is only on our
> native GL path, and not with ANGLE), it doesn't seem to me that this test
> should be using antialiasing. A problem with antialiasing shouldn't fail it
> even though the issue it's supposed to be testing passes.
> >
> > Just disabling antialiasing in this test would keep this test specific.
> If we want to test for the antialiasing artifacts that are causing this test
> to fail, I think we should make that a separate test.
> >
> >
> > -Jeff
> >
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