Have you ever tried gazing at a slightly stained blank wall and seeing an odd figure forming out of it? It sounds odd, doesnt it? And please try not to stare at the blank wall with your mouth open :).
Probably crazy, but this could be a dynamic technique of seeing something really existing and naturally forming from a permanent wall. Sometimes it is fascinating you almost feel like getting a charcoal pencil to follow the lines through it. No, you wouldn't want to ruin a great wall like some kind of ancient caveman from the Near East.

Click this thumbnail to see a caveman :-)
This is how to make it practical and true to life. Get a pencil and an old piece of paper or board. Be sure the paper is quite textured or has creases of oldness in it and not immaculately blank. Now what can you make up with that old paper? Okay. Just look at it plainly and try to imagine a figure out of the creases. Pay close attention to anything taking shape in it. If you think you have seen something like a mountain, landscape, human head, nude woman, and whatever
get the pencil and trace the perceived figure. You will be surprised as if the image is inked on the paper and the outcome is marvelous! It is like making love with your imagination.
Do try those exercises. Those methods helped me a lot in effective, instant drawing ever since I was a kid. And after a while, the capability to imagine becomes natural like seeing a depth out of nothing. It is a sort of pasting a virtual image into a cruel piece of BLANK paper and as the mind vividly develops the FOCUS, gradually the hands begin tracing it.
How Important is FREEHAND DRAWING or simply DRAWING?
It is important to know your goals and the reason why you want to learn. This is self-explanatory just to remind the importance of the capability to sketch. No student has ever received a diploma on graduation day without doing sketching stuff for school projects. Parents must have the skill to draw to teach their kids. If you are a designer, all technical drawings will not get accomplished if you just rely in using T-squares and triangles. Most of the time, the mind is freer to draw if not disturbed by mechanical tools.

DRAWING in serious or in technical field is the graphical or visual representation of any documents. That is why a house, bridge, industrial arts/designs, buildings, mechanical details, etc., must have "construction drawings" or plans in blueprints, as a part of documents, because what could not be explained in words must be DRAWN before technically specified.
Now, practically, freehand drawing is simply sketching but one of the tools of communication any average individual has used all their lives. If one asks, "Where do you live?" Replying: "I live at blah-blah-blah
" is not sufficient. You have to sketch the map to make it clear. So everything is self-explanatory. Even the cavemen used it as a tool in expressing themselves.
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