/usr/share/psychtoolbox-3/PsychDemos/DriftDemo5.m is in psychtoolbox-3-common 3.0.11.20131230.dfsg1-1build1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 | function DriftDemo5(angle, cyclespersecond, f, drawmask)
% function DriftDemo5(angle, cyclespersecond, f, drawmask)
% ___________________________________________________________________
%
% Display animated gratings using the new Screen('DrawTexture') command.
%
% The demo shows two drifting sine gratings through circular apertures. The
% 1st drifting grating is surrounded by an annulus (a ring) that shows a
% second drifting grating with a different orientation.
%
% The demo ends after a key press or after 20 seconds have elapsed.
%
% The demo uses alpha-blending and color buffer masking for masking the
% gratings with circular apertures.
%
% Parameters:
%
% angle = Angle of the grating with respect to the vertical direction.
% cyclespersecond = Speed of grating in cycles per second. f = Frequency of
% grating in cycles per pixel.
% drawmask = If set to 1, then a gaussian aperture is drawn over the grating
% _________________________________________________________________________
%
% see also: PsychDemos, MovieDemo
% HISTORY
% 4/1/09 mk Adapted from Allen Ingling's DriftDemo.m
if nargin<4
% By default, we mask the grating by a gaussian transparency mask:
drawmask=1;
end;
if nargin<3
% Grating cycles/pixel
f=0.05;
end;
if nargin<2
% Speed of grating in cycles per second:
cyclespersecond=1;
end;
if nargin<1
% Angle of the grating: We default to 30 degrees.
angle=30;
end;
movieDurationSecs=20; % Abort demo after 20 seconds.
texsize=300; % Half-Size of the grating image.
try
AssertOpenGL;
% Get the list of screens and choose the one with the highest screen number.
screenNumber=max(Screen('Screens'));
% Find the color values which correspond to white and black.
white=WhiteIndex(screenNumber);
black=BlackIndex(screenNumber);
% Round gray to integral number, to avoid roundoff artifacts with some
% graphics cards:
gray=round((white+black)/2);
% This makes sure that on floating point framebuffers we still get a
% well defined gray. It isn't strictly neccessary in this demo:
if gray == white
gray=white / 2;
end
inc=white-gray;
% Open a double buffered fullscreen window with a gray background:
[w screenRect]=Screen('OpenWindow',screenNumber, gray);
% Calculate parameters of the grating:
p=ceil(1/f); % pixels/cycle, rounded up.
fr=f*2*pi;
visiblesize=2*texsize+1;
visible2size=visiblesize/2;
% Create one single static grating image:
% MK: We only need a single texture row (i.e. 1 pixel in height) to
% define the whole grating! If srcRect in the Drawtexture call below is
% "higher" than that (i.e. visibleSize >> 1), the GPU will
% automatically replicate pixel rows. This 1 pixel height saves memory
% and memory bandwith, ie. potentially faster.
[x,y]=meshgrid(-texsize:texsize + p, 1);
grating=gray + inc*cos(fr*x);
[x2,y2]=meshgrid(-texsize/2:texsize/2 + p, 1);
m=cos(fr*x2);
grating2=gray + inc*m;
% Store grating in texture:
gratingtex=Screen('MakeTexture', w, grating);
grating2tex=Screen('MakeTexture', w, grating2);
% Create a single gaussian transparency mask and store it to a texture:
mask=ones(2*texsize+1, 2*texsize+1, 2) * gray;
[x,y]=meshgrid(-1*texsize:1*texsize,-1*texsize:1*texsize);
mask(:, :, 2)=white * (1-(x.^2 + y.^2 <= texsize^2));
masktex=Screen('MakeTexture', w, mask);
% Definition of the drawn rectangle on the screen:
dstRect=[0 0 visiblesize visiblesize];
dstRect=CenterRect(dstRect, screenRect);
% Definition of the drawn rectangle on the screen:
dst2Rect=[0 0 visible2size visible2size];
dst2Rect=CenterRect(dst2Rect, screenRect);
% Query duration of monitor refresh interval:
ifi=Screen('GetFlipInterval', w);
waitframes = 1;
waitduration = waitframes * ifi;
% Recompute p, this time without the ceil() operation from above.
% Otherwise we will get wrong drift speed due to rounding!
p=1/f; % pixels/cycle
% Translate requested speed of the grating (in cycles per second)
% into a shift value in "pixels per frame", assuming given
% waitduration: This is the amount of pixels to shift our "aperture" at
% each redraw:
shiftperframe= cyclespersecond * p * waitduration;
% Perform initial Flip to sync us to the VBL and for getting an initial
% VBL-Timestamp for our "WaitBlanking" emulation:
vbl=Screen('Flip', w);
% We run at most 'movieDurationSecs' seconds if user doesn't abort via
% keypress.
vblendtime = vbl + movieDurationSecs;
i=0;
% Animationloop:
while (vbl < vblendtime) && ~KbCheck
% Shift the grating by "shiftperframe" pixels per frame:
xoffset = mod(i*shiftperframe,p);
i=i+1;
% Define shifted srcRect that cuts out the properly shifted rectangular
% area from the texture:
srcRect=[xoffset 0 xoffset + visiblesize visiblesize];
src2Rect=[xoffset 0 xoffset + visible2size visible2size];
% Draw grating texture, rotated by "angle":
Screen('DrawTexture', w, gratingtex, srcRect, dstRect, angle);
if drawmask==1
% Draw aperture over grating:
Screen('DrawTexture', w, masktex, [0 0 visiblesize visiblesize], dstRect, angle);
end;
% Disable alpha-blending, restrict following drawing to alpha channel:
Screen('Blendfunction', w, GL_ONE, GL_ZERO, [0 0 0 1]);
% Clear 'dstRect' region of framebuffers alpha channel to zero:
Screen('FillRect', w, [0 0 0 0], dst2Rect);
% Fill circular 'dstRect' region with an alpha value of 255:
Screen('FillOval', w, [0 0 0 255], dst2Rect);
% Enable DeSTination alpha blending and reenalbe drawing to all
% color channels. Following drawing commands will only draw there
% the alpha value in the framebuffer is greater than zero, ie., in
% our case, inside the circular 'dst2Rect' aperture where alpha has
% been set to 255 by our 'FillOval' command:
Screen('Blendfunction', w, GL_DST_ALPHA, GL_ONE_MINUS_DST_ALPHA, [1 1 1 1]);
% Draw 2nd grating texture, but only inside alpha == 255 circular
% aperture, and at an angle of 90 degrees:
Screen('DrawTexture', w, grating2tex, src2Rect, dst2Rect, 90);
% Restore alpha blending mode for next draw iteration:
Screen('Blendfunction', w, GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
% Flip 'waitframes' monitor refresh intervals after last redraw.
vbl = Screen('Flip', w, vbl + (waitframes - 0.5) * ifi);
end;
Priority(0);
Screen('CloseAll');
catch
%this "catch" section executes in case of an error in the "try" section
%above. Importantly, it closes the onscreen window if its open.
Screen('CloseAll');
Priority(0);
psychrethrow(psychlasterror);
end %try..catch..
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