Bug 998703 - WebGL: incorrect draw of round splats
Summary: WebGL: incorrect draw of round splats
Keywords:
Status: CLOSED EOL
Alias: None
Product: Fedora
Classification: Fedora
Component: xorg-x11-drv-intel
Version: 19
Hardware: Unspecified
OS: Linux
unspecified
medium
Target Milestone: ---
Assignee: Adam Jackson
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2013-08-19 20:03 UTC by Jannik
Modified: 2015-02-17 16:50 UTC (History)
5 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed: 2015-02-17 16:50:19 UTC
Type: Bug
Embargoed:


Attachments (Terms of Use)
a screenshot of potree, demonstrating the problem (393.42 KB, image/png)
2013-08-19 20:03 UTC, Jannik
no flags Details
correct draw as a comparison (499.57 KB, image/png)
2013-08-19 20:05 UTC, Jannik
no flags Details

Description Jannik 2013-08-19 20:03:38 UTC
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) {
        discard;
}

I attached screenshots of the potree demo, showing the issue, in case you can't reproduce it.

Comment 1 Jannik 2013-08-19 20:05:55 UTC
Created attachment 788193 [details]
correct draw as a comparison

Comment 2 Martin Stransky 2013-08-26 11:08:30 UTC
I see. I guess it's related to OpenGL implementation and/or graphics drivers. Which HW/drivers do you run?

Comment 3 Jannik 2013-08-26 14:05:58 UTC
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 11:14:57 UTC
Works as expected for me so it looks like a driver problem. Moving to X.

Comment 5 Fedora End Of Life 2015-01-09 19:31:23 UTC
This message is a notice that Fedora 19 is now at end of life. Fedora 
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Comment 6 Fedora End Of Life 2015-02-17 16:50:19 UTC
Fedora 19 changed to end-of-life (EOL) status on 2015-01-06. Fedora 19 is
no longer maintained, which means that it will not receive any further
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