Diamond Depth Perception – a user reports

Hi everyone,

I’ll start with a bit of background. I’m Ben’s younger brother, Nick, and I was very keen to see how his software works. Other than mild short-sightedness, I do not think there is anything wrong with my eyes. Sitting in Ben’s office, I noticed a 3D magic eye picture on the wall, and commented that I have never been able to see the 3D image, even though I had a book full of pictures as a child. I tried it again; no success.

We started with the triangles [Ben : the standard conflict scene] and they were overlaid as expected. When we got to the cyan and yellow semicircles within white circles, I noted the horizontal offsets between the semicircles, but everything was flat. There was no depth, and the outer white diamond that encloses the entire image was square.

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I noticed that I could consciously fade either the cyan or yellow semicircles to being invisible (and control the brightness at levels in between) but I really didn’t understand the instructions, which were to select the circle that was ‘closest’. Everything was still flat and I ended up choosing the semicircles that matched closest. This was not right and I kept selecting the wrong circle!

I then tried moving my focal distance (the point at which both eyes converged) closer then further away and noticed that I could move the semicircles sideways to get them to join into a full circle. By doing this several times for each pair, I could figure out which circle was ‘closest’ entirely by feeling my eye muscles. Did this circle ‘feel’ closer because my eyes were more cross-eyed?… But this wasn’t particularly sensitive and sometimes circles were very similar and I had to adjust my eyes several times on each circle to feel a difference. Still flat though!

Then I looked into the black space in the middle of the screen, relaxed my eyes (I was probably staring into the distance) and BAM, I could see the four circles were distorted and had depth. Also, the outer diamond was bowed toward me. Keeping my eyes on this black space, it was easy to judge the relative distances of the circles. After a few rounds, I was able to look around the image and maintain the 3-dimensional illusion at all times.

I guess the purpose of this post is that I want to share my discovery that seeing the image in 3D is not necessarily automatic. It took me a few stages for it to happen: manually varying my distance of focus and figuring out this distance based on my eye muscles, then staring into the middle of the screen before the 3D became apparent. Perhaps I have been unable to separate the two process of focussing (which is done with the lens in each eye) and depth perception (which uses the two eyes together). Certainly, when trying the 3D magic eye pictures my eyes have been staring into the distance (correct!) but my focussing was too (incorrect!) so the image was just a blur. Time to find that old book! I hope this helps someone. Best of luck.

Nick