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MatVis format: MatVis('function name', additional parameters...)
Function: 'LUT' and 'LUT8'
Load a RGB look up table (LUT) for a particular trial.
Parameters :
('LUT8', [red], [green], [blue], start, stop)
('LUT', trialNumber, nTable, [red], [green], [blue])
trialNumber = The particular trial/condition the LUT is for.
nTable = The number of the LUT that is to be loaded.
[red], [green], [blue] = These three vectors contain the LUT values for the corresponding video gun display colors
( 0-255).
Return:
1 = indicates an internal error occurred in MatVis
0 = successful completion of command
Description:
The LUT8 function canbe used to alter the 'default' LUT when trial specific LUTs have not been defined.The functions
supports changing just a portion of the hardware lut using the start and stop parameters (start >= 1, stop <=256).
The length of the input vectors should be stop-start+1.
Alternatively, the trialLUT function is used to declare the number of LUTs are to be associated with a particular
trial. Later this LUT function is used to load into MatVis the individual LUT's for the predefined trial. LUT's
only apply to video modes of 8 bits deep. The red, green and blue LUT vectors are of length 256. Values in the
LUT vectors indicate the strength/voltage or intensity for that particular LUT color and location in the LUT. Values
in the spatial image arrays are actually indexes to the color LUT which determine the final display intensity of
each video gun for that image pixel location. Many animation techniques involving frame by frame changes in the
LUT's without any change in the actual spatial pattern.
Examples:
1) A spatial ramp pattern (each row contains the numbers 0 - 255) has been loaded into frame one of trial 6.
Use this function to assign a LUT to that trial that would result in a high contrast greyscale 8 cycle/screen sinewave
grating on the video display.
MatVis('LUT', 6, 1, sine(0:255)*250, sine(0:255)*250, sine(0:255)*250);
2) Change the default LUT so it better takes in to consideration the inherant video display gamma non-linearity.
MatVis('LUT8', [0:255].^0.4 * 255/9.18, [0:255].^0.4 * 255/9.18, [0:255].^0.4 * 255/9.18, 1, 256);
See Also:
temporalLUT trial
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