# Screen('Flip') don't clear problem **URL:** \ **Category:** Uncategorized\ **Created:** [August 30, 2008, 4:27am UTC](https://psychtoolbox.discourse.group/t/screen-39-flip-39-don-39-t-clear-problem/1997 "2008-08-30T04:27:58Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![auda.tw](https://avatars.discourse-cdn.com/v4/letter/a/a9adbd/32.png) [@auda.tw](https://psychtoolbox.discourse.group/u/auda.tw)\ **Post date:** [August 30, 2008, 4:27am UTC](https://psychtoolbox.discourse.group/t/screen-39-flip-39-don-39-t-clear-problem/1997/1 "2008-08-30T04:27:58Z")
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 ---
**Author:** ![mariokleiner](https://avatars.discourse-cdn.com/v4/letter/m/13edae/32.png) [@mariokleiner](https://psychtoolbox.discourse.group/u/mariokleiner)\ **Post date:** [August 31, 2008, 2:59pm UTC](https://psychtoolbox.discourse.group/t/screen-39-flip-39-don-39-t-clear-problem/1997/2 "2008-08-31T14:59:30Z")
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](mailto:psychtoolbox@yahoogroups.com), "auda.tw" \ 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 > \>