IWISTER #3 – The Puzzle Pyramid

Click for the interactive version

This latest Interactive Wireframe Stereogram took a lot of work. It may seem similar to the Puzzle Cube, but the subtle differences are quite significant and required a major rewrite.

In this puzzle all four pieces are identical, and they snap together whenever two sides fit, regardless of whether it is the correct match or not. This makes for a more interesting challenge. And if you realise that you attached a piece wrongly, you can detach it again.

It’s more fun than it sounds like, trust me. Why not give it a try?

IWISTER #2 – The Puzzle Cube


The new IWISTER (Interactive Wireframe Stereogram) is out!  This one gives you four different 3D shapes, which you can move around freely. Your task is to assemble them into a cube.

Have a go at it, and then come back and leave a comment below!

How do stereograms work?

In an earlier post I introduced the Wireframe Stereogram and mentioned that it grew out of a need to simplify stereograms. I needed to be able to generate them fast enough for an interactive display, and the typical SIRDS, SIS and MTS kind of stereograms took too long to produce, at least with my very basic technology and programming skills. To illustrate that, here’s a little introduction to stereograms and how they work.

The most basic type of stereogram is the stereo pair. This was all the rage just a few years after photography was invented, and today we can find lots of stereophotographs on flickr and the like.

stereo pair

Our brain has many ways to work out depth in a visual scene. The one that stereograms make use of is stereopsis, where the brain compares the two slightly different views our eyes have of the same scene, and interprets the differences as depth. Stereograms simply present these two different views next to each other, and it’s then up to you to look at the left view with your left eye, and the right view with your right eye (in stereograms designed for “parallel”, or divergent, viewing).

This works great, but we can only present very narrow scenes. Once the views start overlapping, the pair may still look ok in 2D, but once we fuse the stereo pair, we realise there’s a problem in 3D; now, our brain gets confused as to which scene the overlapping areas belong to, because there is conflicting information.

overlapping stereo pair

That’s where the Single Image Stereograms come in. Be it Random Dot (SIRDS), patterned (SIS), Mapped Texture (MTS) or whatever, they make sure that overlapping areas look the same in both views, eliminating that conflict. In other words, an MTS like the one below re-colours the left and right parts of the cube so they look the same when they overlap in the two views.

mapped texture stereogram

There are many ways to do this, but all of them take a lot of computation to work out what colour each pixel should be so it looks right on all the surfaces it ends up on in the 3D scene. That takes too much time to do it in real-time for an interactive display.

The Wireframe Stereogram eliminates that problem by getting rid of all the surfaces of the objects in the scene, and making all edges the same colour. This means that the two views we are combining are mostly transparent, and where edges in both views cross, they are the same colour, so there is no conflict.

wireframe stereogram

Of course, loosing all the surfaces and textures is a great sacrifice, and a Wireframe Stereogram will never have the same impact as a good Mapped Texture Stereogram. But this is compensated by the fact that we can now move things around in the 3D scene in real time. (To experience that, check out the Interactive Wireframe Stereograms.) We can’t have everything…

The rabbit is fast catching up on the tiger

The Year of the Tiger is in its final few days, with the Year of the Rabbit just around the corner. And since the long gestation of my Interactive Wireframe Stereogram (IWISTER) was coming to an end just recently, I thought I might launch IWISTER with a Chinese New Year theme.

rabbit maze stereogram

This is the initial frame of the interactive stereogram. You may be able to complete the maze mentaly in this static and reduced image, but it is a lot more fun to actually move the rabbit along the lines and guide it to the carrot. Click on the image to get to the interactive version, and once you’re done, you may want to come back here to comment on it… ; )

Gong Xi Fa Cai!

A new kind of stereogram

Stereograms have been my thing ever since I first figured out how they work some 15 years ago. I went through several rounds of re-invigorated interest, each time developing my technique a bit further. Initially, it was random dot stereograms, which quickly moved on to those with basic background images. Then I figured out how to map textures onto the 3D shapes and enhance their contours. All of these had been done before, but in my latest round I think I have come up with something original – nothing revolutionary, or even surprising, but something I haven’t come across anywhere else yet: the Wireframe Stereogram.

This new kind of stereogram grew out of two separate ambitions I had. The first was to create paintable stereograms – images that can be transferred onto canvas with traditional painting techniques. The second was to simplify the stereograms so much that they can be generated on the fly, fast enough to respond to a user’s input in an interactive display. And the result turns out to have a third benefit, too: a simple wireframe stereogram seems to be easier to fuse than other types, which apparently helps stereogram novices to see the 3D effect.

I may write about just how all this came about some other time. For now, here’s a first example of a basic wireframe stereogram – a design I used for a Season’s Greetings card recently.

Wireframe Stereogram