Stimulus flicker and non-uniform colours

[Tyler]

When I run a PsychoPy experiment the stimuli either flicker or appear
with non-uniform (gradient) colour.

For example, let's say I run the "psychophysicsStaircase" demo. When
the instructions appear, instead of appearing as solid white text they
have a marble-like texture. Each letter is coloured with a white-black
gradient. If I run the "sternberg" demo, when the instructions appear
the letters all flicker between solid white and that same gradient
texture. Similarly, a colour patch stimulus produces the same
behaviour.

Does anyone have any idea why this is?

I'm running PsychoPy under Windows 7 with an ATI Radeon HD 5670 and
the latest Catalyst drivers.

[Tyler]

I have a few of things to add this morning.

First, I tried changing some settings that seemed relevant.
1) Forced vsync is now on in my Catalyst Control Center.
2) Full-screen mode is off in the experiment.
3) The experiment is now displayed at a lower resolution (1024x768).

Then, I noticed that when I take a screenshot of the experiment while
it's running, the screenshot comes out appearing as it should. I can
only assume that this means the gradient is caused by the flicker and/
or refreshing of the display. Next, I checked the debug file and it is
reporting a frame rate of 60.

When I posted yesterday I was running on version 1.71, so I updated to
1.73 which was released very recently.

I noticed that an instance of BOINC was running in the background,
which was also tapping into GPU processes. I turned it off.

Still no luck. Is there anything else I should consider?

[Jonathan Peirce]

I'm afraid I've got no idea what would cause this. Never heard anything
like it reported before. Can you try on another monitor?

I would normally turn full-screen mode on for better timing but I can't
imagine why that would cause rendering glitches like this.

Maybe you could send in a copy of the output from the sysinfo demo. At
least for info's sake.

Jon

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Jonathan Peirce
Nottingham Visual Neuroscience

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[Tyler]

One new observation I've made this morning: not all experiments
produce this behaviour. I loaded some of the coder demos and I found
mixed results.

I created a video showing a number of these demos running:
face_jpg.py, textStimuli.py, starField.py, shapes.py, dots.py,
customTextures.py, and textStimuli_pygame.py.

It's hard to figure out what exactly is going on, since there don't
seem to be any consistent patterns emerging. Also, bear in mind the
slower frame-rates were caused by the screencast software running
alongside PsychoPy, and further, because this strange behaviour was
captured with screencast software you can be sure it's not the monitor
I'm using.

Finally, here is the sysinfo output:

-----

Welcome to PsychoPy2!
v1.73.02

##### Running: C:\Program Files (x86)\PsychoPy2\lib\site-packages
\psychopy-1.73.02-py2.6.egg\psychopy\demos\coder\sysInfo.py #####
System info:
Windows-7-6.1.7601-SP1

Python info
C:\Program Files (x86)\PsychoPy2\pythonw.exe
2.6.6 (r266:84297, Aug 24 2010, 18:46:32) [MSC v.1500 32 bit (Intel)]
numpy 1.6.0
scipy 0.9.0
matplotlib 1.0.1
pyglet 1.1.4
PsychoPy 1.73.02

OpenGL info:
vendor: ATI Technologies Inc.
rendering engine: ATI Radeon HD 5670
OpenGL version: 4.1.10428 Compatibility Profile Context
(Selected) Extensions:
True GL_ARB_multitexture
True GL_EXT_framebuffer_object
True GL_ARB_fragment_program
True GL_ARB_shader_objects
True GL_ARB_vertex_shader
True GL_ARB_texture_non_power_of_two
True GL_ARB_texture_float
max vertices in vertex array: 2147483647
1.0614 WARNING Creating new monitor...

-----

[Tyler]

Err, here is a link to the video I was talking about: http://screencast.com/t/v3xntX0BMP

[Jonathan Peirce]

The textures have weird diagonal lines in them. That, in the past, has occurred on some systems whil trying to use interpolation (although I haven't seen it occur with text before, nor introduce extra colours). With the face demo could you try adding the parameter
    interpolate=False
when the face stimulus is created? And try with it set to True and False? (make sure you use the capital first letter and no quotation marks). That will just give me some idea about whether this is the same issue. But I've never actually owned a machine that did this to 'tinker' with which is annoying.

thanks,
Jon

On 25/01/2012 16:33, Tyler wrote:

Err, here is a link to the video I was talking about: http://screencast.com/t/v3xntX0BMP

[Tyler]

Hi Jon,

I added interpolate=False to each of the visual.PatchStims in
face.jpg.py, but the rotating face still appears with those diagonal
lines in both cases. Flipping interpolate to True didn't have any
effect either.

I'd be willing to try anything else you can think of.

Tyler

[Jonathan Peirce]

OK, I do now have a lab machine that I can replicate this on (which I
guess is dubiously good news).

I've also identified that older versions (definitely 1.60) don't do it.
That's good because it means it can presumably be fixed.

So now I have to go figure out exactly which change caused the problem,
and why it only happens on some machines (my development PC, running
win7 with an ATI 5400 seems not so different from your but works fine!)

Jon

--

[Jonathan Peirce]

OK, the problem is caused by the line GL.glVertex(10,10) in win.flip()
which is used to draw a pixel for waitblanking.

Your weird colors will go away if you set waitBlanking=False when
creating the window.

And I'll try to find an alternative command to draw something really
small that doesn't corrupt this particular windows/ATI configuration.

Jon

[Tyler]

I just wanted to confirm that the patch worked on my end also. Thanks!