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From: bugzilla-daemon@freedesktop.org
To: dri-devel@lists.freedesktop.org
Subject: [Bug 93594] Flickering Shadows in The Talos Principle
Date: Fri, 19 Feb 2016 10:17:18 +0000	[thread overview]
Message-ID: <bug-93594-502-7UkHTNSJzB@http.bugs.freedesktop.org/> (raw)
In-Reply-To: <bug-93594-502@http.bugs.freedesktop.org/>


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https://bugs.freedesktop.org/show_bug.cgi?id=93594

--- Comment #18 from Kai <kai@dev.carbon-project.org> ---
(In reply to Marek Olšák from comment #10)
> (In reply to Michel Dänzer from comment #9)
> > Note that AFAIK using things like derivatives in non-uniform control flow
> > isn't supported by GLSL. What's the original GLSL shader?
> 
> True.
> 
> The GLSL shader is using discard followed by fwidth. This is undefined
> behavior.
> 
> Therefore, it's an application bug.
> 
> The easy workaround would be to disable register allocation in st/mesa to
> get a quasi-SSA form and trivially move KILL_IF to the end of the shader if
> the app is detected to be Talos Principle.

I forwarded this information to Croteam and Dean Sekulic answered:
> Oh, just found out that discard instruction is treated as dynamic flow control
> for some reason... :/
>
> Will fix this!
>
>
> On 19-02-16 8:21, Dean Sekulic wrote:
>> I can't find any reference anywhere that doing fwidth() (or ddx/ddy for
>> that matter) after discard should be undefined behavior... :/
>>
>> GPUs should handle that case completely fine.
>>
>> Can you elaborate, please?

Looks like there might be an update for The Talos Principle which will address
this.

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  parent reply	other threads:[~2016-02-19 10:17 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-05 15:16 [Bug 93594] Flickering Shadows in The Talos Principle bugzilla-daemon
2016-01-06  3:01 ` bugzilla-daemon
2016-01-06 18:59 ` bugzilla-daemon
2016-01-06 19:08 ` bugzilla-daemon
2016-01-07  8:58 ` bugzilla-daemon
2016-01-07 23:45 ` bugzilla-daemon
2016-01-07 23:50 ` bugzilla-daemon
2016-02-14  4:21 ` bugzilla-daemon
2016-02-17  1:17 ` bugzilla-daemon
2016-02-17  1:55 ` bugzilla-daemon
2016-02-17 16:51 ` bugzilla-daemon
2016-02-17 17:21 ` bugzilla-daemon
2016-02-17 21:12 ` bugzilla-daemon
2016-02-17 23:20 ` bugzilla-daemon
2016-02-18  1:17 ` bugzilla-daemon
2016-02-18 15:07 ` bugzilla-daemon
2016-02-18 15:25 ` bugzilla-daemon
2016-02-18 16:06 ` bugzilla-daemon
2016-02-19 10:17 ` bugzilla-daemon [this message]
2016-02-19 16:41 ` bugzilla-daemon
2016-02-19 20:05 ` bugzilla-daemon
2016-02-20  0:34 ` bugzilla-daemon
2016-02-20 10:17 ` bugzilla-daemon
2016-02-20 21:22 ` bugzilla-daemon
2016-02-22  1:00 ` bugzilla-daemon
2016-02-23  0:06 ` bugzilla-daemon
2016-02-25 21:46 ` bugzilla-daemon
2016-02-26 10:34 ` bugzilla-daemon

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