There are plenty tutorials online on how to create 3D red/cyan anaglyphs from existing photos in Photoshop or similar software. However, I'm wondering if it is possible to draw a 3D image by hand on for example a whiteboard using markers.
My plan is to tape together a red and blue marker and draw with it using the same rotation/inclination of the marker across the drawing. Will this give a 3D effect when viewed through red/cyan glasses? Or is the 3D anaglyph method more complex than just offsetting red and cyan lines?
As it may be possible in theory to draw an anaglyph stereoscopic image by hand this process is rather complicated.
Our brain will compute the third dimension from the two independent flat 2D projections of our world to the retina of our eyes. Both the right eye and the left eye will see the objects from a different angle. This will lead to a shift in the position of the objects in relation to each other.
To simulate this in stereoscopic images we therefore need two flat images viewed from a different angle. The horizontal shift of object positions will depend on their distance from the eye. Therefore simply drawing two separated lines (as was propsed by using a pen with a cyan and a red ink on a shifted position) will not lead to a stereoscopic effect.
Only if the shift of objects for the left and for the right eye was correct we will get a proper stereoscopic effect:
We will have to calculate the shift of each object in relation to its neigbours for each distance from the view point. This can be done with the help of computer algorithms but it is very hard to get that right manually.
Initially the two different images needed for each eye were simply put next to them and were viewed with the cross-eye technique or using a stereoscope with two lenses. To also be able to view large scale images or prints the anaglyph 3D technology was developed as early as in the 19th Century. This technique makes use of a a pair of glasse with two colored filters for each eye and the complemtary color used in the print. Hence a cyan (or green) line will show dark with a red glass, whereas a red line will become dark with a cyan glass.
By just copying the above simple anaglyph with a pen on paper we can easily easily see that the stereoscopic effect which had worked fine on our computer monitor is extremely hard to paint on white paper. We simply can not easily draw a coloured line in subtractive color mode to be invisible when looking through a filter of the same color.
If we do not get the color perfecty right we will see ghost shadows which may eventually even destroy the stereoscopic effect if too strong. This will also often be the case for anaglyphs which were great on the monitor but are disappointing when printed on paper.
I cannot offer any information on how to do this yourself, but it was revealed in one of the production videos for The Hobbit that artists Alan Lee and John Howe produced some hand-drawn red/cyan 3D concept art.
We thought we'd try and come up with some way of actually incorporating a 3D aspect into the way that we were producing the concept art that might communicate more clearly to Peter and to the other technicians. So what we're doing is two drawings. One is in red, one is in blue and the 3D glasses have a red lens and a blue lens, one for each eye.
However, they don't offer much explanation behind their process. The artwork still had to be manipulated (presumably using a computer) to produce the final composite:
Side note: I do have a pair of 3D glasses handy, and it does indeed work!