Wrangle Node Example - Bend Grey Lines Illusion

Inspired from the "Cafe Wall Illusion" example on http://brainden.com/line-illusions.htm I implemented this in Houdini.
Again, pointwrangle and copy nodes make this very easy to implement.

The overall network appears below:

Since we are in Houdini we can experiment, the image at the top of the page is with just the horizontal lines grey.

Below are additional grey lines between the bricks and then a version with black lines: