Often when creating visual stimuli it can be more intuitive to work in polar coordinates (polar angle, radius) than cartesian coordinates (x, y). Note the use of a new function in the above code, 2cart. Keeping up with the tradition of this lesson, we can create a compelling size illusion (called the Ebbinghaus illusion) using a few circles: We can increase that a bit to give smoother circles (at the cost of more computation and storage requirements): import psychopy.visual Try to improve the draw time performance of 2, in particular when text has not. The strategy used by some other libraries is to ask participants to resize a rectangle on the screen until it is the same size of a physical. That is because the circle needs to be approximated with a set of points, and psychopy uses 32 by default. PsychoPy looks for plugins in directories specified by the user in preferences. Notice though that the edges of the circle are not all that smooth. The critical parameter for a circle is its radius. Rect = (win=win, units='pix')Ĭircles can also be useful, and are created by psychopy’s Circle. In such a stimulus, a large number of rectangles of varying widths and heights are drawn at random positions-which ends up producing a pleasant variegated stimulus: import random import psychopy.visualĪ class of visual stimuli that makes heavy use of rectangles are the so-called Mondrian patterns. The two critical arguments are the height and width of the rectangle. We can also create rectangles, using psychopy’s Rect. For example, by drawing a few lines we can create a Ponzo illusion, where the upper horizontal bar looks a bit bigger than the lower horizontal bar: import psychopy.visual Many visual illusions can be created using simple line arrangements. We can also change the colour of the line using lineColor and its width using lineWidth: import psychopy.visual The two critical arguments to create a line are start and end, which are each two-item lists that specify the x and y coordinates of the start and end points of the line, respectively.įor example, to draw a line from the bottom left to the top right of our screen, we could do: import psychopy.visual Perhaps the most simple “shape” stimulus is a line, which we can create in psychopy using Line.

Using psychopy, we can also easily draw a variety of shapes. Be able to generate and display stimuli formed from a variety of shapes (lines, rectangles, circles).

Psychopy draw rectangle