3D on a screen

Among the existing methods, I choose to apply the parallel view method for the pictures not exceeding 200 pixels in width per view, and the cross-eye view method for the larger views.

With each view of 200 pixels, the width on the screen of a computer at 72 pixels per inch is 70mm for each. It is the maximum which is possible to superimpose without a specific viewing device.

The left eye looks at the left view placed on the left.
The right eye looks at the right view placed on the right.

A mask 150x60mm with two windows 40x25mm helps viewing. The distance between the two windows is 20mm so the distance of axis of the two windows is equal to the space between the eyes. Two slide frames could be used also as a mask. With experience, this mask is unnecessary.

Each view must be looked at with the corresponding eye. It is sometimes necessary to lean the head from right to left to get the vertical matching of the objects.

CROSS-EYE VIEW METHOD

The left eye looks at the left view placed on the right.
The right eye looks at the right view placed on the left.

Follow the method on the right column.

A cardboard mask may ease to cross the eyes.

To make this mask, open this drawing and calculate the side C of the square to cut in accordance with the lengths as shown.
C = E.M./ (E + M)
E is the distance between eyes and M the width of one picture.
In the example below, M=100mm, E=65mm so C = 40 mm.

Position the mask so that when closing the left eye, the right eye watches exactly the right view through the window. Do the same with the other eye. Set the mask forward or backward such that each view is matching the window.



Then look at with the two eyes through the window. It is sometimes necessary to lean the head from right to left to get the vertical matching of the objects.
Tips:
Quickly close alternatively each eye, and then open both. Or squint to the middle of the bottom edge of the window before to look at through.