% Clear the workspace and the screen sca; close all; clear; % Here we call some default settings for setting up Psychtoolbox PsychDefaultSetup(2); % Get the screen numbers. This gives us a number for each of the screens % attached to our computer. % For help see: Screen Screens? screens = Screen('Screens'); % Draw we select the maximum of these numbers. So in a situation where we % have two screens attached to our monitor we will draw to the external % screen. When only one screen is attached to the monitor we will draw to % this. % For help see: help max screenNumber = max(screens); % Define black (white will be 1 and black 0). This is because % luminace values are (in general) defined between 0 and 1. % For help see: help BlackIndex black = BlackIndex(screenNumber); % Open an on screen window and color it black % For help see: Screen OpenWindow? [window, windowRect] = PsychImaging('OpenWindow', screenNumber, black); % Get the size of the on screen window in pixels % For help see: Screen WindowSize? [screenXpixels, screenYpixels] = Screen('WindowSize', window); % Get the centre coordinate of the window in pixels % For help see: help RectCenter [xCenter, yCenter] = RectCenter(windowRect); % Make a base Rect of 200 by 200 pixels. This is the rect which defines the % size of our square in pixels. Rects are rectangles, so the % sides do not have to be the same length. The coordinates define the top % left and bottom right coordinates of our rect [top-left-x top-left-y % bottom-right-x bottom-right-y]. The easiest thing to do is set the first % two coordinates to 0, then the last two numbers define the length of the % rect in X and Y. The next line of code then centers the rect on a % particular location of the screen. baseRect = [0 0 200 200]; % Center the rectangle on the centre of the screen using fractional pixel % values. % For help see: CenterRectOnPointd centeredRect = CenterRectOnPointd(baseRect, xCenter, yCenter); % Set the color of our square to full red. Color is defined by red green % and blue components (RGB). So we have three numbers which % define our RGB values. The maximum number for each is 1 and the minimum % 0. So, "full red" is [1 0 0]. "Full green" [0 1 0] and "full blue" [0 0 % 1]. Play around with these numbers and see the result. rectColor = [1 0 0]; % Draw the square to the screen. For information on the command used in % this line see Screen FillRect? Screen('FillRect', window, rectColor, centeredRect); % Flip to the screen. This command basically draws all of our previous % commands onto the screen. See later demos in the animation section on more % timing details. And how to demos in this section on how to draw multiple % rects at once. % For help see: Screen Flip? Screen('Flip', window); % Now we have drawn to the screen we wait for a keyboard button press (any % key) to terminate the demo. % For help see: help KbStrokeWait KbStrokeWait; % Clear the screen. "sca" is short hand for "Screen CloseAll". This clears % all features related to PTB. Note: we leave the variables in the % workspace so you can have a look at them if you want. % For help see: help sca sca;