Bug 998703 - WebGL: incorrect draw of round splats
WebGL: incorrect draw of round splats
Product: Fedora
Classification: Fedora
Component: xorg-x11-drv-intel (Show other bugs)
Unspecified Linux
unspecified Severity medium
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Assigned To: Adam Jackson
Fedora Extras Quality Assurance
Depends On:
  Show dependency treegraph
Reported: 2013-08-19 16:03 EDT by JannikV
Modified: 2015-02-17 11:50 EST (History)
5 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2015-02-17 11:50:19 EST
Type: Bug
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RHEL 7.3 requirements from Atomic Host:
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Attachments (Terms of Use)
a screenshot of potree, demonstrating the problem (393.42 KB, image/png)
2013-08-19 16:03 EDT, JannikV
no flags Details
correct draw as a comparison (499.57 KB, image/png)
2013-08-19 16:05 EDT, JannikV
no flags Details

  None (edit)
Description JannikV 2013-08-19 16:03:38 EDT
Created attachment 788192 [details]
a screenshot of potree, demonstrating the problem

Description of problem:
While viewing a WebGL Model which is drawn as a point-cloud, the splats are not round, even if the fragment shader tries to discard all pixels outside the incircle.

Version-Release number of selected component (if applicable):
todays Firefox Aurora build (and earlier) on Firefox 19

Steps to Reproduce:
1. open a point-cloud WebGL application which tries to draw round splats, like http://potree.org/demo/lion/lion_takanawa.html
2. zoom in and set the point-size to a lower value, like 0.2
3. choose "Weighted Points" in the drop down list

Actual results:
the splats look like a quarter of a circle or a triangle

Expected results:
the splats should be round

Additional info:

This bug is not limited to Firefox. Chrome shows the same behaviour. And it is _not_ reproducible on Debian or Windows. That's the reason why I fill the bug here, and not in bugzilla.mozilla. I've chosen firefox as component, because I don't know which part of Fedora is responsible for WebGL / OpenGL related operations. Maybe someone can concretize this.

Notice the difference between "Weighted Points" and "Filtered Points" in the potree demo.

I have a similar application which suffers from this bug. The fragment shader looks like this:
float dist = distance(gl_PointCoord, vec2(0.5, 0.5));
    if(dist >= 0.5) {

I attached screenshots of the potree demo, showing the issue, in case you can't reproduce it.
Comment 1 JannikV 2013-08-19 16:05:55 EDT
Created attachment 788193 [details]
correct draw as a comparison
Comment 2 Martin Stransky 2013-08-26 07:08:30 EDT
I see. I guess it's related to OpenGL implementation and/or graphics drivers. Which HW/drivers do you run?
Comment 3 JannikV 2013-08-26 10:05:58 EDT
Thanks for looking into..

$ glxinfo | grep 'OpenGL renderer'
OpenGL renderer string: Mesa DRI Intel(R) Ironlake Mobile

Maybe this is also useful:

00:02.0 VGA compatible controller: Intel Corporation Core Processor Integrated Graphics Controller (rev 02) (prog-if 00 [VGA controller])
	Subsystem: Hewlett-Packard Company Device 144a
	Flags: bus master, fast devsel, latency 0, IRQ 43
	Memory at c0000000 (64-bit, non-prefetchable) [size=4M]
	Memory at b0000000 (64-bit, prefetchable) [size=256M]
	I/O ports at 5050 [size=8]
	Expansion ROM at <unassigned> [disabled]
	Capabilities: <access denied>
	Kernel driver in use: i915

Let me know if you need additional info.
Comment 4 Martin Stransky 2013-08-29 07:14:57 EDT
Works as expected for me so it looks like a driver problem. Moving to X.
Comment 5 Fedora End Of Life 2015-01-09 14:31:23 EST
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Comment 6 Fedora End Of Life 2015-02-17 11:50:19 EST
Fedora 19 changed to end-of-life (EOL) status on 2015-01-06. Fedora 19 is
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