Video Wall of Terror

This weekend, I helped decorate for a Halloween Party at my sister’s house. There’s an odd hallway that connects their main large public room to the rest of the house. It’s used for storage, and has shelves on both sides.

This year, I decided to decorate that area by creating a video wall effect. Something like a Television Control Room of Terror!

To start with, I simply filmed my brother-in-law with a video camera – only from WAY TOO CLOSE! I shot macro video of his eye and mouth. Then I edited the footage to create a custom looping DVD.

In the hallway, I set up multiple monitors. These are old monochrome standard definition monitors that were on their way to the recycling center. They were professional monitors, which means that they can pass a video signal through from one monitor to another, making it easy to daisy chain several monitors.

Next to the monitors, I set up three DVD players (including one car DVD player – hey I use what I got!) to play the three different custom DVDs – Right Eye, Left Eye, and Mouth. Each of the three videos is a different length, so they will continue to drift out of sync. That way, as they loop, the visuals are a continuingly changing experience through the whole evening.

Above the monitors, I set up a video camera on a tripod and fed it to some of the monitors. That way, when party-goers look at the monitor, they also see themselves. Having feedback on some of the monitors adds a sense of interactivity to the project.

After the monitors and DVD players were all set up, I covered the rest of the shelving with black paper. In a dark hallway, lit only be black lights, it’s a great effect of creepy images floating in the hall.

If you want more details on this project, I made a full step-by-step write-up on Instructables.

Dynamic Sculpture – Update 1

I am collaborating with the Betty Brinn Children’s museum to create something similar to this.

This sculpture has 844 balls hanging from strings wound around a pulley on a DC motor shaft. Ours will feature somewhere between 320 to 500 balls. I am currently working on a prototype to test and qualify different electronic and control platforms. It’s made out of 40mm x 40mm aluminum extrusion, laser cut wood motor mounts, 5V steppers, and ULN2003 based stepper drivers. I have been using an Arduino mega for now to test the motor and drivers.



The next step is to write software to create “voxels” with instructions akin to G-code. Additional software will be necessary to simulate the animation. G-code like instructions will be used by microcontrollers to control steppers in order to create an animation.

Gothic Arch Room Divider is Finished (Sort of….)

Sanctuary and More 102Silversark put together an amazing fashion show on Friday to showcase pieces she made inspired by church architecture and her trip to the Netherlands. This is something I cooked up for a background piece for the show.

The design work took several months and the actual creation of the piece took about a week, working 12-16 hours a day.  The frame is made from CNC routed aspen (thanks, Jason H.!) which is a rather “fuzzy” wood and required two days to hand finish, including the use of a set of needles files to smooth out the inset edges.

The acrylic panels were hand-stained with Gallery Glass stain and simulated liquid leading. They’re not quite finished yet, but I plan to complete the staining within the next week.

I’ll also be using this as a backdrop for various events including the Sustainability Summit coming up as well as the Concinnity sci-fi/gaming convention on April 5th. Additionally, this might be making its way to Embellishments in the Grand Avenue Mall for a window decoration.

I can’t wait to make another one!

How To Laser Cut Really Big Halftone Photos

Wanting to up the ante a bit after having the Makerspace laser cutter chop out hundreds of city blocks to form a big map of MKE, I decided to laser cut a  24” by 18” halftone image!  As it required the laser cutter to carve 10368 circles out of an off-yellow piece of 98 Lb paper, the cutting took 1.3 hours and produced quite a bit of confetti.  I’ll display this with a purple (rather than black) paper behind the off-yellow laser cut paper.  In person there is an interesting transition from an abstract purple/yellow shape into a black and white image as one moves further away from the image.  You may even want to sit back from your monitor to improve the “image quality.”


Check out this video of the laser cutter in the middle of cutting 10000 circles!  Note the mysterious logic employed by the laser cutter to determine the order of its cuts.

I imported a photo into GIMP, and desaturated it to produce a black and white image.  After bumping up the contrast and darkening it slightly to nearly saturate the darkest areas (and avoid any totally white areas), I brought it into Inkscape.  Inkscape can create halftones in a two step, manual process.  The first step is to draw an 8 pixel by 8 pixel circle in the upper left corner of the 1133×720 pixel image, and select Edit->Clone-> Create Tiled Clones.  To create a rectangular grid of halftone dots whose sizes are set by the color of the image below, use these settings:


From a quick test cut of a particularly dark area, I found that I needed to add an offset between each row and each column to account for the kerf of the laser.  I.e. the laser beam has a cutting width that is wider than that of the line, and so in the darkest areas of the photo the halftone dots overlapped, causing a large section of the paper to fully detach. That led me to make this test strip with 11 shades of grayscale, evenly spaced between pure black and white.  I laser cut this test strip with various offset distances between the rows and columns in order to arrive at the optimal 10% extra offset between adjacent rows and columns shown in the above settings. Note also that the smallest size circles may not even be exported from Inkscape due to their infinitesimal dimensions (i.e. if you export as a .pdf).  The minimum gap between circles with 42% speed and 100% power on an 1133 pixel wide image blown up to 24″ is 0.79 pixels, which is 0.017″.

test_tripApplying these same settings to the image created a 128 by 81 array of circles, for a grand total of 10368 vector objects.  In my first trial run last weekend, I found that sending this much data to our 60 Watt Universal Laser takes 5 minutes and results in a print error I noticed only after hitting start!  After 1.3 hours of vector cutting, I found that a few of the rows and columns were shifted a bit from their intended location.  It’s not clear whether this had to do with the print error, or if the paper moved slightly during the cutting process.

In order to improve the second version (shown at top), I chose to move away from the rectangular grid of halftone dots – recall that Kays and London teach that hexagonal close packing is for champions.  The reason to abandon the rectangular spacing is to improve the dynamic range (i.e. to make the blacks blacker).  For example, rectangular grids of circles pack at an “efficiency” of Pi/4, which is 79%, whereas hexagonal close packing results in a pi/6*sqrt(3) packing, or 91%.  That means that the darkest sections of the image will be darker, as more of the light colored “front” piece of paper can be cut away.  See the image below, and note that the hexagonal pattern does indeed appear darker.


It turns out that Inkscape doesn’t easily permit this.  I ended up spending an hour or two fiddling with the column and row offset settings using my 11 black/white tone test strip to find settings that gave the hexagonal offset with the closest, even hexagonal spacing between adjacent circles.  The following settings worked great for an 8 by 8 dot on the darkest square of the test strip:

hex_arrayI test cut this yesterday, sending ¼ of the data at a time to the laser to avoid printing errors. However, part way through the cutting, cut-out paper circles stuck to the long air assist nozzle of the laser head (ironically) hit a washer I was using to weigh down the paper to prevent movement while cutting. The paper shifted by about 1mm, which was enough to make some adjacent halftone dots overlap and cause others to have a visibly wider spacing.

In the process of cutting that photo, Shane happened by and mentioned that vector cutting 10368 objects may be just as fast as the typically-very-slow raster cutting time.  With three clicks, I turned off the vector outline of the halftone dots, and selected a fill color.  After test cutting a row, I found that he was right.  Check out the difference between raster  (100% speed, 100% power) and vector (42% speed, 100% power) in the darkest section of the image – the area with the closest spaced circles:


The vector halftone dots are perfectly circular, though the edges are a bit rough.  Some of them have a very small border and so are a bit fragile.  The raster halftone dots are not very circular, but the edges are very smooth and the boarders are slightly wider.  I chose to raster cut the 24″ x 18″ image, and found that the raster cutting time of 1.4 hours was nearly equal to the 1.3 hour vector cutting time.

Note that many programs can create halftones, though often the results will not be suitable for laser cutter use:


The next step is to laser cut this image into wood.  Also, Inkscape will let you draw any shape to create tiled clones from – so please do share photos of any halftone images you create with star shapes!