Luggage refit

When traveling on business, I take my favorite piece of luggage, the rolling folding garment bag. I bought this a few years ago, and it's now been on several trips and has been hauled around various city sidewalks in different weather. It's gotten beaten up a fair bit. The last such trip that I remember it was on was Copenhagen in winter time—I remember rolling it to the hotel from the metro on cold, slushy pavement. That did a number on the bag's bottom that tends to drag on the ground when I overstuff it. I've been re-applying duct tape to the bottom as a way to prevent more damage, but having to replace this every trip was becoming a sticky, gooey mess. The last trip I took it on (to San Antonio), the bag came back with the handle screws ripped through the bag's top fabric (maybe the third time this has happened). I knew it would happen, it was only a matter of time. Previously, the plastic backing that was there had broken and so the only thing between the handle bolts (on the outside) and the nuts (on the inside) was fabric. It couldn't last. So for a long time I've been thinking about some kind of backing, but I couldn't decide on what to put in there. Plastic? That would break sooner or later. Wood? No...I can't remember what made me finally think of it, but aluminum was finally what I came up with. At the hardware store I found two cheap pieces of aluminum that seemed just the right size: one for the inside, the other as a kind of guard plate to replace the duct tape. The above pics show one of the plates (trimmed with tin snips) going in. I had to drill four holes and had to get the alignment just right to get the handle to line up. At bottom are two more pics of the outside. The plate took 12 bolts (stainless) to hold in place. I used rubber washers to prevent moisture from seeping in. I used oversized fender washers underneath all the nuts to ensure that they don't rip through the plastic/fabric. Hopefully this will hold for a while.

Oh, I should also add that the wheels you see above are roller-blading wheels that I bought at a sporting goods store. I've replaced the factory-made luggage wheels twice now. Both times they (Victorinox) were good enough to send me a pair for free, but all three pairs (including the original) were fairly cheap plastic things, which these sort of rubber bands glued to the outside. All three pairs wore out rather quickly. The roller-blade wheels are solid, roll pretty well, and hopefully should be more durable. So far so good—the couple of trips they've been on they've performed really well. And they're fairly distinct so picking out the bag from the rest similar black rollies on the luggage carousel was fairly easy. That aluminum backing plate should also help.

Real-time heatmaps

Some of you already know what the above images are about, but I'm so happy about getting this to work, that I thought I'd post a blog about it. It happens to coincide with the end of this year's REU (Research Experience for Undergraduates) program during which I had 5 undergrads in the lab working on several eye tracking projects. This year it was all about video, which prompted me to develop the program responsible for drawing the above images. Collecting eye movement data (x,y,t) over video is what I worked on in Barcelona. It took me pretty much most of those 6 weeks to get enough C/C++ code together to be able to display video while recording gaze data. Once that was done, I handed the program over to the REUs who then ran four studies and who also extended the program to do various other things. Meanwhile, the whole effort motivated me to figure out how to display the captured data atop the video frames as a means to visualize the recorded gaze data. The algorithm for generating the above heatmaps is pretty straightforward and is well-known. Step 1 involves dropping a Gaussian point-spread function at each gaze location, growing the resultant heightfield with as many gaze points as collected per each video frame. Step 2 requires finding the maximum value in the heightmap. Sounds easy, but for an NxN image, it takes O(N^2) operations. Step 3 then requires normalization of the heightfield (division by the max value). Step 4 then recolors the height (luminance) by mapping it to the rainbow color palette. The last two steps, which can be combined into one, together take another O(N^2) steps. The image above at left was created this way for a data set of 24 scanpaths (sequence of gaze points) on the CPU. Looks good but it's slow (took about a minute). The image at right took only a fraction of a second and looks almost identical. The trick here is to use the GPU to reduce the number of operations form order O(N^2) to O(log(N)) for the max value localization and O(1) for the recoloring. On one particular workstation with a decent graphics card I observed a 700-fold speedup due to these reductions. That just blew me away, which is why I'm so excited about this development. I recently moved that bit of GPU code onto my video playing code and sure enough, even for a fairly large data set (oh, about 8 people or so), the code appears to play the video at real-time (30 Hz) rates. I suppose I should take timings of this just to confirm how long it takes...this could make a nice little paper someplace. Other eye tracking types might like to know how the whole thing is put together...

Reedy River Gig

The pic is back from our gig on July 7th. Right in the middle of a heat wave, when it went up to 98F. If I look like I'm trying to concentrate, I was. I don't know whether it was the heat, the Gretsch drums, or something else or a combination of factors, but I was not having a good first set. I think it played ok, but I know I made a couple of flubs here and there. I pulled out my old Gretsch drums but I haven't played on them in a very long time. Lately I've been playing on the Tama rockstar kit I traded for my old Pintech electronic set. I like the Tama's larger toms and I think its compactness—one less floor tom. The Gretsch kit has two floor toms and maybe because of that seems more spread out. I remember missing the right crash symbol because it was out of my immediate reach (had to stretch for it). So after the gig I transferred the bass drum's resonant head (with the band name on it) onto the Tama kit and bagged the Tama kit. I don't think I'll be using the Gretsch kit any more, so it may be time to start looking for a new owner for that kit. Right during setup I busted a resonant head on the small 10" tom...it sounded kinda crappy the rest of the night, another reason for a lackluster first set...once I got into the habit of going for the second tom, and the temperature went down, the second set was much better.

Greenville Gig at Reedy River

Tomorrow the Hoodoo Hounds play at the Reedy River Nighttime Concert Series. Just ahead of this gig we got a story on us printed in the Greenville News, our local city paper, as you see above. The full story can be found here.

4th of July

As soon as I got back from Barcelona, it was straight back to work. I was already a week behind on my meetings with this year's REU students, so it's been pretty hectic. Today is the last day of the 4th of July long weekend, and since I'm stuck at home on the couch, I thought I'd update the blog. Somehow I managed to pull my left pec muscle a couple of days ago, which is why I'm sitting here coding and not out on the boat. I guess it must have been lugging the new sailboat battery that did it, but I can't be sure. All I know is my left pec is so painful that it's difficult to breathe. I wanted to get out on the sailboat, give it a nice cleaning, and putt around on it, but I'm having trouble moving around much. It's nice to have caught up to some badly needed coding, but it's really nice outside, too... Hopefully this goes away by tomorrow, because that's when I need to load up the truck with my drum gear for Wednesday's Greenville gig. Tonight is band practice, when I'll see how I can play in this condition. Major annoyance. Anyway, above is a short video of the fireworks that the city of Clemson puts on every year at the YMCA beach. We get out there on the motorboat and sit and watch (a major reason for getting the powerboat back in '03 I think it was—the idea was to have it on the water by July 4th—I think we got it in the water just in time). This is the first video upload I've done on the blog, hopefully it turns out ok. I shot the vid on my iPhone, so it may be a little blurry, although I think it managed to focus itself fairly well.