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
|
function ProceduralColorGratingDemo(color1,color2,baseColor)
% ProceduralColorGratingDemo() -- demo color grating procedural shader
% stimuli
%
%
% This demo shows how to use procedural color gratings. Color gratings
% have two color sources, rather than one. They are a useful stimulus
% class for e.g. understanding opponenet color channels. The standard PTB
% grating shader cannot generate this class of grating. The procedural
% shader can generate sinusoidal or square wave gratings, and you can set a
% radial aperture.
%
%
% Optional Inputs are:
% color1 -- the first color of the grating, default is red [1 0 0 1]
% color2 -- the second color of the grating, default is green [0 1 0 1]
% baseColor -- the base color from which color1 and color2 are blended
% depending on contrast. Normally this would be set to your background
% color in PTB; default in this demo is the background color [0.5 0.5 0.5 1].
%
% History:
% 01/03/2020 initial version (Ian Andolina)
if ~exist('color1','var') || isempty(color1)
color1 = [1 0 0 1];
end
if ~exist('color2','var') || isempty(color2)
color2 = [0 1 0 1];
end
if ~exist('baseColor','var') || isempty(baseColor)
baseColor = [0.5 0.5 0.5 1];
end
% Setup defaults and unit color range:
PsychDefaultSetup(2);
% Disable synctests for this quick demo:
oldSyncLevel = Screen('Preference', 'SkipSyncTests', 2);
% Select screen with maximum id for output window:
screenid = max(Screen('Screens'));
% Open a fullscreen, onscreen window with gray background. Enable 32bpc
% floating point framebuffer via imaging pipeline on it, if this is possible
% on your hardware while alpha-blending is enabled. Otherwise use a 16bpc
% precision framebuffer together with alpha-blending.
PsychImaging('PrepareConfiguration');
PsychImaging('AddTask', 'General', 'FloatingPoint32BitIfPossible');
[win, winRect] = PsychImaging('OpenWindow', screenid, baseColor);
% Query frame duration: We use it later on to time 'Flips' properly for an
% animation with constant framerate:
ifi = Screen('GetFlipInterval', win);
% Enable alpha-blending
Screen('BlendFunction', win, 'GL_SRC_ALPHA', 'GL_ONE_MINUS_SRC_ALPHA');
% default x + y size
virtualSize = 512;
% radius of the disc edge
radius = floor(virtualSize / 2);
% Build a procedural texture, we also keep the shader as we will show how to
% modify it (though not as efficient as using parameters in drawtexture)
texture = CreateProceduralColorGrating(win, virtualSize, virtualSize,...
color1, color2, radius);
% These settings are the parameters passed in directly to DrawTexture
% angle
angle = 45;
% phase
phase = 0;
% spatial frequency
frequency = 0.03;
% contrast
contrast = 0.5;
% sigma < 0 is a sinusoid.
sigma = -1.0;
% Preperatory flip
showTime = 3;
vbl = Screen('Flip', win);
tstart = vbl + ifi; %start is on the next frame
while vbl < tstart + showTime
% Draw a message
Screen('DrawText', win, 'Standard Color Sinusoidal Grating', 10, 10, [1 1 1]);
% Draw the shader texture with parameters
Screen('DrawTexture', win, texture, [], [],...
angle, [], [], baseColor, [], [],...
[phase, frequency, contrast, sigma]);
vbl = Screen('Flip', win, vbl + 0.5 * ifi);
phase = phase - 15;
end
%--- now we switch to a square wave grating using sigma >= 0
% if sigma is 0 then the squarewave is not smoothed, but if it is > 0 then
% hermite interpolation smoothing in +-sigma of the edge is performed.
sigma = 0.1;
% Preperatory flip
vbl = Screen('Flip', win);
tstart = vbl + ifi; %start is on the next frame
while vbl < tstart + showTime
% Draw a message
Screen('DrawText', win, 'Standard Color Squarewave Grating', 10, 10, [1 1 1]);
% Draw the shader texture with parameters
Screen('DrawTexture', win, texture, [], [],...
angle, [], [], baseColor, [], [],...
[phase, frequency, contrast, sigma]);
vbl = Screen('Flip', win, vbl + 0.5 * ifi);
phase = phase - 15;
end
%--- Lets make a Blue/Yellow colour shader
Screen('Close',texture);
texture = CreateProceduralColorGrating(win, virtualSize,...
virtualSize, [0 0 1 1], [1 1 0 1], radius);
% Preperatory flip
vbl = Screen('Flip', win);
tstart = vbl + ifi; %start is on the next frame
while vbl < tstart + showTime
% Draw a message
Screen('DrawText', win, 'Blue-Yellow Color Squarewave Grating', 10, 10, [1 1 1]);
% Draw the shader texture with parameters
Screen('DrawTexture', win, texture, [], [],...
angle, [], [], baseColor, [], [],...
[phase, frequency, contrast, sigma]);
vbl = Screen('Flip', win, vbl + 0.5 * ifi);
phase = phase - 15;
end
%--- now we change the baseColor to show its effect on the grating
baseColor = [0.2 0.0 0.2 1];
% Preperatory flip
vbl = Screen('Flip', win);
tstart = vbl + ifi; %start is on the next frame
while vbl < tstart + showTime
%draw the background with the same baseColor
Screen('FillRect',win, baseColor);
% Draw a message
Screen('DrawText', win, 'Blue-Yellow Grating modifying the base color', 10, 10, [1 1 1]);
% Draw the shader texture with parameters
Screen('DrawTexture', win, texture, [], [],...
angle, [], [], baseColor, [], [],...
[phase, frequency, contrast, sigma]);
vbl = Screen('Flip', win, vbl + 0.5 * ifi);
phase = phase - 15;
end
% Close onscreen window, release all resources:
sca;
% Restore old settings for sync-tests:
Screen('Preference', 'SkipSyncTests', oldSyncLevel);
|
