% 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. screens = Screen('Screens'); % To 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. screenNumber = max(screens); % Define black and white (white will be 1 and black 0). This is because % in general luminace values are defined between 0 and 1 with 255 steps in % between. With our setup, values defined between 0 and 1. white = WhiteIndex(screenNumber); black = BlackIndex(screenNumber); % Do a simply calculation to calculate the luminance value for grey. This % will be half the luminace value for white grey = white / 2; % Make our window transparent Transparence is in the 0 (fully transparent) to % 1 (fully opaque) range opacity = 0.8; PsychDebugWindowConfiguration([], opacity) % Open an on screen window using PsychImaging and color it grey. [window, windowRect] = PsychImaging('OpenWindow', screenNumber, grey); % Now we have drawn to the screen we wait for a keyboard button press (any % key) to terminate the demo. KbStrokeWait; % Clear the screen. sca;