outObj = GPUTypeFromToGL(cmd, inObj [, glObjType][, outObj][, keepmapped][, mapflags])

Note: Calling this command requires calling the following command first
to initialize Psychtoolbox GPU computing support:

PsychImaging(‘AddTask’, ‘General’, ‘UseGPGPUCompute’, ‘GPUmat’);

Supported ‘cmd’ commands

if cmd is zero, then convert an OpenGL object of type glObjType,
referenced by handle inObj into a GPU object and return it in outObj. If
the optional outObj is provided as input argument, try to recycle it –
just fill its content with OpenGL object’s content. Otherwise, create an
outObj of matching format for content. If ‘keepmapped’ is set to 1, the OpenGL
object will stay mapped for the GPU compute api, otherwise it gets immediately
unmapped after the conversion. Keeping the object mapped is more efficient, but
requires more careful management of objects to prevent malfunctions.

If cmd is == 1, then convert GPU object inObj to OpenGL object of type
glObjType and return it in outObj. Try to recycle a passed in outObj, if
possible, otherwise create a new one. ‘keepmapped’ - see explanation for cmd zero.

If cmd is == 2, then unmap the OpenGL object. You must do this if you previously
set the optional ‘keepmapped’ flag to 1 during a copy operation and now want to
use the object which was the source or the target of that copy again with OpenGL
or Screen(), ie., with a Psychtoolbox drawing or image processing function.
Unmapping is neccessary for proper OpenGL operation, but costs a fraction of a
millisecond of overhead on well working operating systems like Linux. Clever use
of the ‘keepmapped’ flag and this manual unmapping method sometimes allows to
save some redundant unmap calls.

If cmd is == 3, then remove the OpenGL object from use by the GPU compute toolkit.
This must be done before destroying/deleting the OpenGL object, e.g., before
a call to Screen(‘Close’, x); for a window or texture handle x. This operation
can be very expensive – on the order of multiple milliseconds, so use sparingly.

If cmd is == 4, all OpenGL objects are removed. Usually used before closing (all)
onscreen windows, e.g., via Screen(‘CloseAll’) or sca. This cache flush is very

If cmd is == 5, then the given OpenGL object ‘inObj’ of type glObjType is mapped
and a CUDA memory pointer is returned, for use with external mex files, so these
can directly access the mapped resource. The object is mapped read-only.

If cmd is == 6, the same operation as cmd == 5 happens, but the object is mapped

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