Chell's arms appear black at some shader levels

[eriktorbjorn]

I recently played through Portal 2 (single player) for the first time. For the most part, I was blown away at how well it worked (once I had gotten it to run). Good job! However, I did notice a graphics glitch near the very end: In most scenes where you see Chell's arms, they appear to be black and featureless, rather than pink.

This only happens on the "High" and "Very High" shader detail levels. If I turn it down to "Medium" or "Low", it looks fine to me. Se the attached screenshots, which are made at "Very High" and "Medium" levels respectively.

(This is reminiscent of issue #150, but that is listed a being fixed already. This glitch is much more noticeable in Portal Stories: Mel, since there you always see the hands while carrying the portal gun.)

As you can see from the information below, I'm using the open-source graphics drivers. While they've improved a lot in recent years, I wouldn't really be surprised if this turns out to be a driver bug rather than a Portal 2 bug.

Processor Information:
Vendor: GenuineIntel
CPU Family: 0x6
CPU Model: 0x3c
CPU Stepping: 0x3
CPU Type: 0x0
Speed: 3400 Mhz
4 logical processors
4 physical processors
HyperThreading: Unsupported
FCMOV: Supported
SSE2: Supported
SSE3: Supported
SSSE3: Supported
SSE4a: Unsupported
SSE41: Supported
SSE42: Supported

Network Information:
Network Speed:

Operating System Version:
Debian GNU/Linux unstable (sid) (64 bit)
Kernel Name: Linux
Kernel Version: 4.0.0-2-amd64
X Server Vendor: The X.Org Foundation
X Server Release: 11701000
X Window Manager: Xfwm4
Steam Runtime Version: steam-runtime-release_2015-01-06

Video Card:
Driver: X.Org Gallium 0.4 on AMD BONAIRE

Driver Version:  3.0 Mesa 10.5.8
OpenGL Version: 3.0
Desktop Color Depth: 24 bits per pixel
Monitor Refresh Rate: 60 Hz
VendorID:  0x1002
DeviceID:  0x6658
Number of Monitors:  1
Number of Logical Video Cards:  1
Primary Display Resolution:  1920 x 1080
Desktop Resolution: 1920 x 1080
Primary Display Size: 18,78" x 10,55"  (21,54" diag)
                                        47,7cm x 26,8cm  (54,7cm diag)
Primary VRAM Not Detected

Sound card:
Audio device: Realtek ALC662 rev1

Memory:
RAM: 7940 Mb

Miscellaneous:
UI Language: English
LANG: en_DK.utf8
Microphone: Not set
Total Hard Disk Space Available: 234123 Mb
Largest Free Hard Disk Block: 45518 Mb

Installed software:

Recent Failure Reports:

[MarkkusBoi]

This is happening to me and I have Intel HD 3000 on Mesa 10.6.

[ghost]

I have this issue, too.
@ Kubuntu 16.04, HD 7950 @ radeonsi, Mesa 11.2.0

[Tele42]

Since this issue is trending to be mesa-only, has it also been reported to the mesa devs to see if they have some insight?

[ghost]

Hi, good idea. I just opened a bug for it, as I couldn't find a report. Hope I did alright, it's my first report.
https://bugs.freedesktop.org/show_bug.cgi?id=96512

If there's anything more to add, please feel free to comment on the ticket

[eriktorbjorn]

For reference, the Mesa bug has been tagged as RESOLVED NOTOURBUG, stating that it

"... uses a shadow sampling instruction on sampler 15, but the texture bound to texture 15 is a 1x1 GL_SRGB texture ... that is, the game is invoking undefined behaviour, hence this is not our bug."

[MarkkusBoi]

I will see if turning off specular and/or phong shading will do anything.

[MarkkusBoi]

Update: On my computer, turning off phong shading (putting mat_phong 0 in the console) will fix the black arms thing. The same black on Chell's arms covers Chell's whole world model except a little hair, by the way.

[libcg]

Could reproduce the bug here too in the ending scene of Portal 2. mesa 12.0.3, R9 Fury.

[MarkkusBoi]

I think that it's safe to say that this is a problem for anybody using Mesa. We now need Valve to investigate further into the rendering code and fix it.

[ghost]

I agree. With the info from the Mesa bug ticket, I think the code-flaw on Valve's side is a fair assumption. Sadly, there doesn't really seem to be activity from Valve on this so far.
I also reported this on September 6th in a Steam support ticket and they said they'd pass my info along, so maybe that is already being investigated - and maybe not. It probably would not hurt for someone else to try something similar to make sure. :) This is a long-standing issue and I really hope it gets fixed sooner rather than later.