NOTE (dhb, 8/19/12). This code is a bit dusty, as it is not
being actively maintained. In particular, the PTB display
control has evolved since this was last looked at carefully.
In general, you want to calibrate through the same set of
display calls you’ll use in your experiment. Below is some
prose written by Mario Kleiner that describes how the PTB
currently wants you to control and restore your clut. In
an ideal world, this routine would be updated to match. But
more generally, if you use this code you may want to modify
to make sure it is displaying colors the same way you will in
your experiments. The actual work is done in CalibrateMonDrvr
and CalibrateAmbDrvr so that is where you would look.
We have two functions for this. [LoadIdentityClut](LoadIdentityClut)() for loading an identity clut and configuring the GPU for identity pixel passthrough, and [RestoreCluts](RestoreCluts), which restores to the state before [LoadIdentityClut](LoadIdentityClut)(). I think "[sca](sca)" calls that, as well as showing the cursor and other cleanup actions. [LoadIdentityClut](LoadIdentityClut) is also automatically called by [PsychImaging](PsychImaging) etc. if the image processing pipeline is used for Bits++/Datapixx/Viewpixx,video attenuators etc. It is important to always use [LoadIdentityClut](LoadIdentityClut)() instead of self-made code. Many (most?) graphics cards on most operating systems have graphics driver bugs and hardware quirks which cause the self-made identity clut to actually not turn out to be an identity clut in the hardware. [LoadIdentityClut](LoadIdentityClut)() has heuristics to detect os/gpu combo and select an appropriately fudged lut to actually get an identity mapping. In case of new hardware with new quirks we should update that files detection logic to cope. Additionally there is [SaveIdentityClut](SaveIdentityClut)() to save a known good lut for automatic use with [LoadIdentityClut](LoadIdentityClut), overriding its choice. And there is [BitsPlusIdentityClutTest](BitsPlusIdentityClutTest) to test a Bits+ or Datapixx device thoroughly for problems and aid in fixing them. It is easy to get fooled into thinking you got it right, even when using a photometer, because some of the problems are subtle and not detectable without use of dynamic test patterns like in [BitsPlusIdentityClutTest](BitsPlusIdentityClutTest) with Mono++ mode, or special debug functionality as in the [DataPixx](DataPixx)/[ViewPixx](ViewPixx) devices. I use a [DataPixx](DataPixx) to test such stuff and PTB has builtin diagnostic to utilize that hardware to make sure that the video signal is really untampered. [LoadIdentityClut](LoadIdentityClut) also calls special functions in [Screen](Screen) that try to workaround or fix other hardware interference. E.g., in addition to cluts messing with pixel passthrough, there is also display dithering on any digital video output, and some new pre- and post-gamma corrections in latest generation hardware -- [Screen](Screen) can fix this for some cards on some operating systems, but only when used through [LoadIdentityClut](LoadIdentityClut). E.g., almost all AMD cards will cause trouble on OSX when the [PsychtoolboxKernelDriver](PsychtoolboxKernelDriver) and [LoadIdentityClut](LoadIdentityClut) etc. is not used, almost all [NVidia](NVidia) cards on OSX will cause trouble unless you use some special [NVidia](NVidia) kernel driver which is somewhere referenced on the Bits+ pages on our wiki. We have/need similar hacks on Windows, e.g., [PsychGPUControl](PsychGPUControl)() for AMD cards. On Linux either PTB's low-level fixes apply or they are not neccessary. So the [CalibrateMonSpd](CalibrateMonSpd) etc. should be fixed to use [LoadIdentityClut](LoadIdentityClut)/[RestoreCluts](RestoreCluts), everything else is just begging for trouble.
7/7/98 dhb Wrote from generic.
dhb dacsize/driver filled in by hand, Screen fails to return it.
4/7/99 dhb NINEBIT -> NBITS.
dhb Wrote version for Radius 10 bit cards.
4/23/99 dhb Change wavelength sampling to 380 4 101, PR-650 native.
9/22/99 dhb, mdr Define boxSize.
8/11/00 dhb Save mon in rawdata.
8/18/00 dhb More descriptive information saved.
8/20/00 dhb Automatic check for RADIUS and number of DAC bits.
9/10/00 pbe Added option to blank another screen while measuring.
2/27/02 dhb Various small fixes, including Radeon support.
dhb Change noMeterAvail to whichMeterType.
11/08/06 cgb, dhb OS/X.
9/27/08 dhb Default primary bases is 1 now. Use RefitCalLinMod to change later if desired.
8/19/12 mk Ask user for choice of display output device.