Weird bug. Run this and you should see a basic procedural garborium demo with correct blending (using normalised 0-1 colour range). Now uncomment line 24 (WhitIndex function) and rerun. What I see is the blending is now different (only the lighter parts of the gabor display); but I don't think WhiteIndex should effect the drawing mode.

gistfile1.matlab

function runGarborium()
s = struct();
s.srcMode = GL_ONE;
s.dstMode = GL_ONE;
s.blend = true;
s.backgroundColour = 0.5;
s.bitDepth = 'FloatingPoint32BitIfPossible';
s.screenid = max(Screen('Screens'));

%-----------------------------------------------------------
try%======This is our main TRY CATCH experiment display loop
%-----------------------------------------------------------
  PsychImaging('PrepareConfiguration');
	PsychImaging('AddTask', 'General', 'UseFastOffscreenWindows');
	PsychImaging('AddTask', 'General', s.bitDepth);
	PsychImaging('AddTask', 'General', 'NormalizedHighresColorRange');
	[s.win, s.winRect] = PsychImaging('OpenWindow', s.screenid, s.backgroundColour);
	if s.blend
		Screen('BlendFunction', s.win, s.srcMode, s.dstMode);
	end
	s.isi = Screen('GetFlipInterval', s.win);
	s.halfisi = s.isi/2;
	s.black = BlackIndex(s.win);
	%s.white = WhiteIndex(s.win);
	
	sz = 65;
	phase = 0;% Phase of underlying sine grating in degrees
	sc = 10.0;% Spatial constant of the exponential "hull"
	freq = .05;% Frequency of sine grating
	contrast = 10.0;% Contrast of grating
	aspectratio = 1.0;% Aspect ratio width vs. height
	ngabors = 200;
	mypars = repmat([phase, freq, sc, contrast, aspectratio, 0, 0, 0]', 1, ngabors);
	
	gabortex = CreateProceduralGabor(s.win, sz, sz, 1);
	
	Screen('DrawTexture', s.win, gabortex, [], [], [], [], [], [], [],kPsychDontDoRotation,...
		[phase, freq, sc, contrast, aspectratio, 0, 0, 0]);
	Screen('Flip', s.win);
	WaitSecs(0.5)
	texrect = Screen('Rect', gabortex);
	inrect = repmat(texrect', 1, ngabors);
	
	dstRects = zeros(4, ngabors);
	scale = zeros(1,ngabors);
	for i=1:ngabors
		scale(i) = 1*(0.1 + 0.9 * randn);
		dstRects(:, i) = CenterRectOnPointd(texrect * scale(i), rand * s.winRect(3), rand * s.winRect(3))';
	end
	% Preallocate array with rotation angles:
	rotAngles = rand(1, ngabors) * 360;
	% Initially sync us to VBL at start of animation loop.
	vbl = Screen('Flip', s.win);
	tstart = vbl;
	count = 0;
	% Animation loop: Run until any keypress:
	while ~KbCheck
		Screen('DrawTextures', s.win, gabortex, [], dstRects,...
			rotAngles, [], [], [], [], kPsychDontDoRotation, mypars);
		Screen('DrawingFinished', s.win);
		%rotAngles = rotAngles + 1 * randn(1, ngabors);
		mypars(1,:) = mypars(1,:) + 5;% Increment phase-shift
		%mypars(5,:) = 1.0 + 0.25 * sin(count*0.1); % "Pulse" the aspect-ratio of each gabor with a sine-wave timecourse
		[x, y] = RectCenterd(dstRects);
		x = mod(x + 0.33 * cos(rotAngles/360*2*pi), s.winRect(3));
		y = mod(y - 0.33 * sin(rotAngles/360*2*pi), s.winRect(4));
		% Recompute dstRects destination rectangles for each patch, given the
		% 'per gabor' scale and new center location (x,y):
		dstRects = CenterRectOnPointd(inrect .* repmat(scale,4,1), x, y);
		vbl = Screen('Flip', s.win, vbl + s.halfisi);
		count = count + 1;
	end
	% Done. Last flip to take end timestamp and for stimulus offset:
	vbl = Screen('Flip', s.win);
	avgfps = count / (vbl - tstart);
	fprintf('\n--->>> %g frames at %g FPS\n',count,avgfps);
	Priority(0);
	ListenChar(0);
	ShowCursor;
	Screen('CloseAll');
	clear s;
catch ME
	Priority(0);
	ListenChar(0);
	ShowCursor;
	Screen('CloseAll');
	clear s;
	rethrow(ME)
end
end