[visionegg] Re: vertical sync, OpenGL, fullscreen mode
- From: Andrew Straw <andrew.straw@xxxxxxxxxxxxxxx>
- To: visionegg@xxxxxxxxxxxxx
- Date: Thu, 27 Feb 2003 13:13:48 +1030
Hi Levy,
I'm glad to hear everything is working on your system! It's always
re-assuring immediately after a release to hear positive feedback.
Obviously I don't have the resources to test it on all possible systems
myself.
These all seem to be common issues. Sometime I'll write up a cohesive
document about all of this. In the meantime, I'll answer the best I
can.
Levi Larkey wrote:
I just installed VisionEgg, and I've been messing around with the
demos. Everything seems to be working except:
1) It appears that something is preventing synching with the vertical
retrace. From what I understand, synching is necessary to avoid
tearing and to get accurate response time measurements. I've looked
at the settings for my video card (Matrox G400) and looked at
Powerstrip too, but I can't find the appropriate settings. Any
suggestions?... The log is copied below.
I don't have a Matrox G400, so I'm no expert on this card. However, my
office mate has a G450, and I don't think he's had any success getting
synchronization with vertical retrace to work, either. I don't know how
much he's tried. I haven't tried. From looking over his shoulder, it
seems the OpenGL implementation on his card seems slow, old (OpenGL 1.1
is pretty long in the tooth), and not accurate (on his card, sinusoidal
gratings get dimmer towards the edge). Perhaps downloading the latest
driver would help these issues. Unless all of them can be addressed, I
wouldn't recommend using the Matrox G400 for experiments (but it's fine
for development).
On win32, the Vision Egg tries to sync with the vertical retrace by
calling the WGL OpenGL extension function wglSwapIntervalEXT(). I
guess it's not implemented by the Matrox drivers. There may be another
way to do it. If you can figure it out, I'd be happy to integrate it
into the Vision Egg, but I don't have time to work on this. (If it's C
calls to particular functions, that's fine -- we'll wrap that so it's
accessible from Python. I don't think calls to DirectX will work,
though.)
2) Apparently I have an older version of OpenGL (1.1.3). Do I need to
get a newer version for VisionEgg to work properly?
The log messages are hopefully fairly accurate about the limitations
you're up against. I don't know of any others. (The grating getting
dim towards the edges seems to be a Matrox OpenGL implementation bug
rather than behavior according to the OpenGL specification.)
3) I get large artifacts when I try to run in fullscreen mode, and the
monitor seems to turn off and then on before displaying the demo. I
know this isn't much to go on, but do you have any suggestions?
The artifacts are probably due to lack of vertical retrace sync and
slow OpenGL implementation. The monitor seeming to turn off and on
again is a result of changing video modes (resolution and refresh rate)
-- your monitor must re-synchronize itself to the new signal
frequencies. It probably behaves similarly if you change refresh rate
or resolution in the Windows control panel.
I hope that helps!
Cheers!
Andrew
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