One of the more advanced features of the Piku-Piku viewer is the ability to dynamically control the perceived depth.
When the Piku-Piku is viewed in its compact form, with a single image, all of the images needed to perceive stereo depth are presented, but at the same time to both eyes. Some people perceive a Pulfrich-like effect, which causes them to experience depth when viewing in this mode.
When you view the Piku-Piku binocularly, your two eyes see two different views. In this view, you can control the interocular separation, which directly determines the amount of depth you perceive. You can dynamically exchange one dimension of space for time.
In today's update, the sliders are shown doubled in the parallel and cross-eye views. You should be able to use them whilst viewing the Piku-Piku. If you have a viewer, or know how to freeview, try it out.
Faces are particularly interesting to look at. Photographers know how the face is flattened by the camera, but you can see the effect for yourself as you change from 3D to 2D.