Tracing is used to transfer an image into line work from a photo or artwork. You place your tracing paper over it and draw the lines that you see. So, Trace it & Sketch it.
So how does it works?
Select an image from the gallery or capture an image with a camera then just apply the filter. After that, you will see that image on the camera screen with transparency & you have to put drawing paper or book anything on which you want to trace and draw. Your image will not appear on paper but a transparent image with camera so that you can trace it on paper.