/usr/share/psychtoolbox-3/PsychDemos/FastNoiseDemo.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 | function FastNoiseDemo(numRects, rectSize, scale, syncToVBL, dontclear)
% FastNoiseDemo([numRects=1][, rectSize=128][, scale=1][, syncToVBL=1][, dontclear=0])
%
% Demonstrates how to generate and draw noise patches on-the-fly in a fast way. Can be
% used to benchmark your system by varying the load. If you like this demo
% then also have a look at FastMaskedNoiseDemo that shows how to
% efficiently draw a masked stimulus by use of alpha-blending.
%
% numRects = Number of random patches to generate and draw per frame.
%
% rectSize = Size of the generated random noise image: rectSize by rectSize
% pixels. This is also the size of the Psychtoolbox noise
% texture.
%
% scale = Scalefactor to apply to texture during drawing: E.g. if you'd set
% scale = 2, then each noise pixel would be replicated to draw an image
% that is twice the width and height of the input noise image. In this
% demo, a nearest neighbour filter is applied, i.e., pixels are just
% replicated, not bilinearly filtered -- Important to preserve statistical
% independence of the random pixel values!
%
% syncToVBL = 1=Synchronize bufferswaps to retrace. 0=Swap immediately when
% drawing is finished. Value zero is useful for benchmarking the whole
% system, because your measured framerate will not be limited by the
% monitor refresh rate -- Gives you a feeling of how much headroom is left
% in your loop.
%
% dontclear = If set to 1 then the backbuffer is not automatically cleared
% to background color after a flip. Can save up to 1 millisecond on old
% graphics hardware.
%
% Example results on a Intel Pentium-4 3.2 Ghz machine with a NVidia
% GeForce 7800 GTX graphics card, running under M$-Windows XP SP3:
%
% Two patches, 256 by 256 noise pixels each, scaled by any factor between 1
% and 5 yields a redraw rate of 100 Hz.
%
% One patch, 256 by 256 noise pixels, scaled by any factor between 1
% and 5 yields a redraw rate of 196 Hz.
%
% Two patches, 128 by 128 noise pixels each, scaled by any factor between 1
% and 5 yields a redraw rate of 360 - 380 Hz.
%
% One patch, 128 by 128 noise pixels, scaled by any factor between 1
% and 5 yields a redraw rate of 670 Hz.
% Abort script if it isn't executed on Psychtoolbox-3:
AssertOpenGL;
% Assign default values for all unspecified input parameters:
if nargin < 1 || isempty(numRects)
numRects = 1; % Draw one noise patch by default.
end
if nargin < 2 || isempty(rectSize)
rectSize = 128; % Default patch size is 128 by 128 noisels.
end
if nargin < 3 || isempty(scale)
scale = 1; % Don't up- or downscale patch by default.
end
if nargin < 4 || isempty(syncToVBL)
syncToVBL = 1; % Synchronize to vertical retrace by default.
end
if syncToVBL > 0
asyncflag = 0;
else
asyncflag = 2;
end
if nargin < 5 || isempty(dontclear)
dontclear = 0; % Clear backbuffer to background color by default after each bufferswap.
end
if dontclear > 0
% A value of 2 will prevent any change to the backbuffer after a
% bufferswap. In that case it is your responsibility to take care of
% that, but you'll might save up to 1 millisecond.
dontclear = 2;
end
try
% Find screen with maximal index:
screenid = max(Screen('Screens'));
% Open fullscreen onscreen window on that screen. Background color is
% gray, double buffering is enabled. Return a 'win'dowhandle and a
% rectangle 'winRect' which defines the size of the window:
[win, winRect] = Screen('OpenWindow', screenid, 128);
% Compute destination rectangle locations for the random noise patches:
% 'objRect' is a rectangle of the size 'rectSize' by 'rectSize' pixels of
% our Matlab noise image matrix:
objRect = SetRect(0,0, rectSize, rectSize);
% ArrangeRects creates 'numRects' copies of 'objRect', all nicely
% arranged / distributed in our window of size 'winRect':
dstRect = ArrangeRects(numRects, objRect, winRect);
% Now we rescale all rects: They are scaled in size by a factor 'scale':
for i=1:numRects
% Compute center position [xc,yc] of the i'th rectangle:
[xc, yc] = RectCenter(dstRect(i,:));
% Create a new rectange, centered at the same position, but 'scale'
% times the size of our pixel noise matrix 'objRect':
dstRect(i,:)=CenterRectOnPoint(objRect * scale, xc, yc);
end
% Init framecounter to zero and take initial timestamp:
count = 0;
tstart = GetSecs;
% Run noise image drawing loop for 1000 frames:
while count < 1000
% Generate and draw 'numRects' noise images:
for i=1:numRects
% Compute noiseimg noise image matrix with Matlab:
% Normally distributed noise with mean 128 and stddev. 50, each
% pixel computed independently:
noiseimg=(50*randn(rectSize, rectSize) + 128);
% Convert it to a texture 'tex':
tex=Screen('MakeTexture', win, noiseimg);
% Draw the texture into the screen location defined by the
% destination rectangle 'dstRect(i,:)'. If dstRect is bigger
% than our noise image 'noiseimg', PTB will automatically
% up-scale the noise image. We set the 'filterMode' flag for
% drawing of the noise image to zero: This way the bilinear
% filter gets disabled and replaced by standard nearest
% neighbour filtering. This is important to preserve the
% statistical independence of the noise pixels in the noise
% texture! The default bilinear filtering would introduce local
% correlations when scaling is applied:
Screen('DrawTexture', win, tex, [], dstRect(i,:), [], 0);
% After drawing, we can discard the noise texture.
Screen('Close', tex);
end
% Done with drawing the noise patches to the backbuffer: Initiate
% buffer-swap. If 'asyncflag' is zero, buffer swap will be
% synchronized to vertical retrace. If 'asyncflag' is 2, bufferswap
% will happen immediately -- Only useful for benchmarking!
Screen('Flip', win, 0, dontclear, asyncflag);
% Increase our frame counter:
count = count + 1;
end
% We're done: Output average framerate:
telapsed = GetSecs - tstart
updaterate = count / telapsed
% Done. Close Screen, release all ressouces:
Screen('CloseAll');
catch
% Our usual error handler: Close screen and then...
Screen('CloseAll');
% ... rethrow the error.
psychrethrow(psychlasterror);
end
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