You've heard of an impossible cube, well this is an impossible Tardis! Inspired by Adam Koford's design on Shirt Woot, I've put my own spin on it, and I'm showing you how to do it too.
pencil (preferably mechanical so you get small clean lines without having to sharpen as often)
thin blue felt tip pen
Draw a horizontal line across your paper and two vertical lines in the middle about a 1/4" apart.
Mark the horizontal line about 3/4" to the left and right of the vertical lines.
Connect the marks with the closest vertical line with two parallel diagonal lines. Remember that throughout this drawing, all the lines will either be parallel with another line or straight vertically.
Connect the two parallel lines with two more on the opposite sides to create a rhombus.
Draw two straight vertical lines from the marks on your horizontal line.
Mirror the top rhombus on the bottom while remembering to keep all the opposite lines parallel to each other.
Keep in mind that this is the basic shape of your tardis, so it should be taller than it is wide.
Add "thickness" to each of the sides by drawing parallel lines on the inside of all the lines you've drawn so far.
Continue to add "thickness" to each of the sides by drawing parallel lines on the inside of all the lines you've drawn so far.
Now you can start to ink your drawing. This will allow you to eliminate some of the extra lines you won't need going forward. Pay close attention to the images to ensure you only ink the lines you want to be in your finished drawing. You can't erase the ink!
In two of the images above, I'm showing a couple places where I messed up the inking. I fixed them in an image editor, but they will be wrong in all the rest of the images.
Finish inking your impossible box and erase your pencil lines.
Now, you're going to begin to turn it into a tardis.
Draw vertical lines from the center and from the second line from the outside edges.
Connect these lines with parallel lines to the center.
Repeat this process but with less height.
Repeat the process on the top to create the basic light shape.
Add the detail lines to the light. Be sure to use downward curved lines to create the illusion of roundness.
Use parallel lines to create the Police Box sign and draw in the words. This may take a bit of trial and error and you may not be able to make the "public call" portion of the sign legible. The Police Box lettering is the most important.
Ink the final lines and erase un-needed pencil.
Color the top of the light and the small layer above the sign.
Now it's time to draw the sides of the tardis. Draw another trapezoid inside the trapezoid shape of the sides and draw a vertical line up the middle of each.
To create the horizontal lines necessary, you'll need to divide the sides of each of these trapezoids by 4.
The easiest way to do that is to measure the side of the outside edge of the trapezoid with a piece of paper and fold it in half twice.
Mark where the paper was folded on the edge of the trapezoid.
Repeat this process with the smaller inside sides.
Connect the lines on either side of the trapezoids.
Now give thickness to each of the lines. Add thickness to both sides of the center line.
Color in around all the squares you've created and add the window detail.
Add thickness to the base with parallel lines on the sides and front.
Draw vertical lines from the corners.
Add additional thickness on the front two lines.
Erase un-needed lines and ink.
Ink the sign and you're done!
I did my drawing on tracing paper, so I could use it as an overlay on a piece of paper with a print. Drawing directly on printed paper doesn't work great when there is a lot of erasing involved as the print can come off as well.
It also allowed me to photograph it over an image of space on my tablet.