Screen('Flip') don't clear problem

1
Hi All,

The 'dontclear' option does not work on my Thinkpad T60p with a ATI
mobility FireGL V5200 graphics card. The command

Screen('Flip', window, [], 1)

gives me the following errors:

Error in function Flip: Usage error
OpenGL AUX buffers unavailable! dontclear=1 in Screen-Flip doesn't
work without them.
Either unsupported by your graphics card, or you disabled them via
call to Screen('Preference', 'ConserveVRAM')?


I understand that some ATI graphics card does not have the required
double buffer capacity. However, in the CATALYST control center, there
are options that allow me to "Enable 8-bit double buffered overlay
planes" and "Force Swap Copy". There is also an option "Enable Quad
Buffer Stereo". Turning them on or off doesn't solve the error message
I have. So my question is: aren't these buffer options relevant to the
OpenGL AUX buffers that are required by PTB3 for the dontclear option
to work properly? Also, when deciding to purchase any video card, what
information should I look for to be sure that the dontclear option
would be supported?

Cheers,

Erik Chang
2
Replace...

window = Screen('OpenWindow', ....);

... by ...

PsychImaging('PrepareConfiguration');
PsychImaging('AddTask', 'General', 'UseVirtualFramebuffer');
window = PsychImaging('OpenWindow', ....);

This will enable a virtual framebuffer - it achieves
the same as use of AUX buffers, just with a different
internal method.

AUX buffers are well supported on Apple OS/X, but
not very well (or not at all) on Windows or Linux. At
the time dontclear=1 was implemented, they were
the only efficient choice.

Have a look at "help PsychImaging", there is more
useful stuff, e.g., support for faster offscreen windows
in the unlikely case you still need them.

-mario


--- In psychtoolbox@yahoogroups.com, "auda.tw" <audachang@...> wrote:
>
> Hi All,
>
> The 'dontclear' option does not work on my Thinkpad T60p with a ATI
> mobility FireGL V5200 graphics card. The command
>
> Screen('Flip', window, [], 1)
>
> gives me the following errors:
>
> Error in function Flip: Usage error
> OpenGL AUX buffers unavailable! dontclear=1 in Screen-Flip doesn't
> work without them.
> Either unsupported by your graphics card, or you disabled them via
> call to Screen('Preference', 'ConserveVRAM')?
>
>
> I understand that some ATI graphics card does not have the required
> double buffer capacity. However, in the CATALYST control center, there
> are options that allow me to "Enable 8-bit double buffered overlay
> planes" and "Force Swap Copy". There is also an option "Enable Quad
> Buffer Stereo". Turning them on or off doesn't solve the error message
> I have. So my question is: aren't these buffer options relevant to the
> OpenGL AUX buffers that are required by PTB3 for the dontclear option
> to work properly? Also, when deciding to purchase any video card, what
> information should I look for to be sure that the dontclear option
> would be supported?
>
> Cheers,
>
> Erik Chang
>