>Psychtoolbox>PsychGLImageProcessing

[warpstruct, filterMode] = CreateDisplayWarp(window, calibfilename [, showCalibOutput=0]);

Helper routine for Geometric display undistortion mapping, not to be
called inside normal PTB scripts!

This function reads a display calibration file ‘calibfilename’ and builds
a “geometric warp function” based on the calibration information in
‘calibfilename’ for the onscreen window with handle ‘window’. It returns
a struct ‘warpstruct’ that defines the created warp function. You could
pass this ‘warpstruct’ as a parameter to the Psychtoolbox command…

PsychImaging(‘AddTask’, viewchannel, ‘GeometryCorrection’, warpstruct);

However, you normally do not call this routine directly from your script. Its
called internally by the PsychImaging() command…

PsychImaging(‘AddTask’, viewchannel, ‘GeometryCorrection’, calibfilename);

…in order to setup PTB’s imaging pipeline for realtime geometry
correction, based on the calibration info in the file ‘calibfilename’.

Example: You created a calibration file ‘mycalib.mat’ to undistort the
left view display of a stereo setup. Then you could apply this
undistortion function via the following setup code:

PsychImaging(‘PrepareConfiguration’);
PsychImaging(‘AddTask’, ‘LeftView’, ‘GeometryCorrection’, ‘mycalib.mat’);
window = PsychImaging(‘OpenWindow’, screenid);

This would open an onscreen window just as window=Screen(‘OpenWindow’, screenid);
would do. It would configure the window for automatic undistortion based
on the data in ‘mycalib.mat’.

Psychtoolbox provides multiple different interactive setup routines that
allow you to create a calibration file for your setup. Currently the
following routines are provided:

DisplayUndistortionBVL.m – Undistortion based on 3rd order polynomial
surface. This is the recommended calibration procedure for most cases -
Proven in real-world use on many different display types.

When used with DisplayUndistortionBVL, the GeometryCorrection takes
up to three optional parameters:

PsychImaging(‘AddTask’, ‘LeftView’, ‘GeometryCorrection’, ‘mycalib.mat’ [, debug=0][, xsampling=73][,ysampling=53][, replicate=[1,1]]);
xsampling and ysampling specify the horizontal and vertical number of subdivisions
for the warpmesh that is used for undistortion - higher numbers give more
close approximations but increase drawing time. replicate is a vector which
describes how often the mesh should be replicated into horizontal and vertical
direction. Values other than the default [1,1] only make sense for special display
devices like ProPixx.

DisplayUndistortionBezier.m – Undistortion based on a NURBS surface (Non
uniform rational bezier spline surface). A simple procedure.

DisplayUndistortionHalfCylinder.m – Undistortion for projection of
images to a half-cylindrical projection surface.

DisplayUndistortionSphere.m – Undistortion for projection of
images to a spherical or half-spherical projection surface.

DisplayUndistortionCSV.m – Import undistortion information from
a .csv file with a warp mesh description suitable for use with NVidia’s
Warp API. This creates a compatible display warping to use of that NVidia
technology.