function [gratingid, gratingrect] = CreateProceduralSquareWaveGrating(windowPtr, width, height, backgroundColorOffset, radius, contrastPreMultiplicator) % [gratingid, gratingrect] = CreateProceduralSquareWaveGrating(windowPtr, width, height [, backgroundColorOffset =(0,0,0,0)] [, radius=inf][, contrastPreMultiplicator=1]) % % Creates a procedural texture that allows to draw square wave grating stimulus patches % in a very fast and efficient manner on modern graphics hardware. % % 'windowPtr' A handle to the onscreen window. % 'width' x 'height' The maximum size (in pixels) of the grating. More % precise, the size of the mathematical support of the grating. Providing too % small values here would 'cut off' peripheral parts or your grating. Too big % values don't hurt wrt. correctness or accuracy, they just hurt % performance, ie. drawing speed. Use a reasonable size for your purpose. % % 'backgroundColorOffset' Optional, defaults to [0 0 0 0]. A RGBA offset % color to add to the final RGBA colors of the drawn grating, prior to % drawing it. % % 'radius' Optional parameter. If specified, a circular aperture of % 'radius' pixels is applied to the grating. By default, no aperture is % applied. % % 'contrastPreMultiplicator' Optional, defaults to 1. This value is % multiplied as a scaling factor to the requested contrast value. If you % specify contrastPreMultiplicator = 0.5 then the per grating 'contrast' % value will correspond to what practitioners of the field usually % understand to be the contrast value of a grating. % % The function returns a procedural texture handle 'gratingid' that you can % pass to the Screen('DrawTexture(s)', windowPtr, gratingid, ...) functions % like any other texture handle. The 'gratingrect' is a rectangle which % describes the size of the support. % History: % 06/06/2011 Modified from PTB function (Ian Andolina). debuglevel = 1; % Global GL struct: Will be initialized in the LoadGLSLProgramFromFiles % below: global GL; if nargin < 3 || isempty(windowPtr) || isempty(width) || isempty(height) error('You must provide "windowPtr", "width" and "height"!'); end if nargin < 4 || isempty(backgroundColorOffset) backgroundColorOffset = [0 0 0 0]; else if length(backgroundColorOffset) < 4 error('The "backgroundColorOffset" must be a 4 component RGBA vector [red green blue alpha]!'); end end if nargin < 5 || isempty(radius) % Don't apply circular aperture if no radius given: radius = inf; end if nargin < 6 || isempty(contrastPreMultiplicator) contrastPreMultiplicator = 1.0; end % Switch to windowPtr OpenGL context: Screen('GetWindowInfo', windowPtr); % Make sure we have support for shaders, abort otherwise: AssertGLSL; if isinf(radius) % Load standard grating shader: gratingShader = LoadGLSLProgramFromFiles('SquareWaveShader', debuglevel); else % Load grating shader with circular aperture support: gratingShader = LoadGLSLProgramFromFiles('SquareWaveApertureShader', debuglevel); end % Setup shader: glUseProgram(gratingShader); % Set the 'Center' parameter to the center position of the grating image % patch [tw/2, th/2]: glUniform2f(glGetUniformLocation(gratingShader, 'Center'), width/2, height/2); glUniform4f(glGetUniformLocation(gratingShader, 'Offset'), backgroundColorOffset(1),backgroundColorOffset(2),backgroundColorOffset(3),backgroundColorOffset(4)); if ~isinf(radius) % Set radius of circular aperture: glUniform1f(glGetUniformLocation(gratingShader, 'Radius'), radius); end % Apply contrast premultiplier: glUniform1f(glGetUniformLocation(gratingShader, 'contrastPreMultiplicator'), contrastPreMultiplicator); glUseProgram(0); % Create a purely virtual procedural texture 'gaborid' of size width x height virtual pixels. % Attach the GaborShader to it to define its appearance: gratingid = Screen('SetOpenGLTexture', windowPtr, [], 0, GL.TEXTURE_RECTANGLE_EXT, width, height, 1, gratingShader); % Query and return its bounding rectangle: gratingrect = Screen('Rect', gratingid); % Ready! return;