“When, Oh draftsmen, you desire to find relaxation in games you should always practice such things as may be of use in your profession, by giving your eye good practice in judging accurately of the breadth and length of objects. Thus, to accustom your mind to such things, let one of you draw a straight line at random on a wall, and each of you, taking a blade of grass or of straw in his hand, try to cut it to the length that the line drawn appears to him to be, standing at a distance of 10 braccia; then each one may go up to the line to measure the length he has judged it to be. And he who has come nearest with his measure to the length of the pattern is the best man, and the winner, and shall receive the prize you have settled beforehand (…) And such games give occasion to good practice for the eye, which is of the first importance in painting.” Leonardo da Vinci – Notebooks
I’ve added to my Patreon account a series of exercises to train your eye-hand coordination and your ability to estimate lengths, angles and distances. You should practice these daily, until you achieve a satisfactory degree of proficiency.
(Level: beginner; Materials needed: several sheets of printer paper, pencil, eraser, a ruler and a protractor)