Windows in a Box

I'm giving virtual machines another go...last time I tried VMware, I thought it sucked. It wasn't free, and what it did not support firewire or accelerated graphics. I don't know (yet) whether this is any better, but I'm giving VirtualBox a try. The idea is to run an eye tracking server in the virtual machine so that I run my OS X client at the same time and thus have both server/client running on one machine. This way when I travel (if I travel with this particular eye tracker), I won't have to lug two laptops around, just my Mac. We'll see how it goes. Right now I have Windows 7 installed, or rather, confined to its virtual box and the eye tracking software is running; I just need to hook it up to the eye tracker itself via USB and see if that works. I was told it would work with Parallels, but I'm going the el-cheapo route first. So far so good...if it works as I hope, then I'll post more on which eye tracker it is and how I find software development for it. Everything should work in Qt, my platform of choice. Oh...the funny thing about Windows is that of course the major part of the installation was Windows Update, what else?! You can see that yet another update was successful :P

Eye tracking station upgrades

I haven't updated the blog in a while, it's been a busy semester. However, it's ending with a lab upgrade that I've been working towards for about a year now. Ever since one of the Windows machines driving one of the eye trackers gave up the ghost and died. It was an old Sun w2100z machine probably past its life expectancy. A replacement was found, but I think they nearly had to pull it out of surplus for me. So this time around instead of mucking about with very large workstations, I decided to replace both server/client at each eye tracker with a Mac Mini. You can see the two little silver boxes in the pic. Each Mac Mini has 8 G of RAM, an Intel Core Duo chip and an Nvidia GeForce 320M chip with 72 GPU cores. Not bad for such a little box! One Mac Mini will be used to run Windows to power the Tobii eye tracker, the other will be used as the client workstation. Since most of my programs work under OS X, I'm hoping that I can develop some cool eye tracking demos on them. Including real-time heatmap rendering and GPU-based scanpath comparison. I'm now just waiting for software installs on them, and testing whether the 400-800 firewire cable will work between the server and the Tobii (it should).

Let there be light!

I had a couple of blog posts in my head that I wanted to put up here, one just from just a couple of days ago, but I don't have the pics handy...instead I'm sitting here waiting for my photon mapper to finish, so I thought I'd write a bit about that...kind of a technical post. I'll try to add a brief pictorial progression so you can see what I'm talking about. At left is a basic ray-traced image that we started with this semester (in a class I'm teaching). It's fairly simple in that we have two spheres, one (the blue one, well it's sort of blue, maybe more like chrome) more reflective than the other, which is more diffuse. There are three lights in the scene but they only show up when reflected (point light sources). The ray tracer demonstrates several concepts: object-oriented hierarchy (spheres and planes are objects), recursion (the rays shot into the scene are reflected recursively), list processing (all objects are on a list), and basic file input/output. Fairly simple, an image like that takes about 3 seconds to render.

The next image in the progression would have been the same as the first, as we explored parallelism. With chip makers now producing multi-core chipsets, one may wonder how to take advantage of the multiple cores or CPUs on the chip? The ray tracer is very well suited to this because each pixel is processed the same way. If we had as many CPU cores as pixels, we could assign each on a one-to-one mapping. My desktop machine in my office has 8 cores, so a simple speedup is to let each of the 8 cores process each of the h/8 rows of pixels. The trick here is to make sure to avoid race conditions, that is, don't let any more than one core write to a piece of shared memory. The ray tracer, in its original conception, had this problem, so this turned out to be a nice exercise, complete with garbage images if done incorrectly. The solution called for each ray to maintain its own state info, which makes perfect sense thinking in parallel. Once that's done, multi-core parallelism is pretty easy, requiring basically one line of #pragma compiler directive to use OpenMP and voila! An almost k-factor speedup for k cores available. Coincidentally, the solution also leads in to the next step of the ray tracer evolution, and that is getting transmission to work right, like you see at right: we not only have reflective objects but transmissive (transparent) ones now.

Once we have the notion of independent rays (in terms of memory access anyway), then it's not a huge conceptual leap to think of photons instead of rays. These are shot from the light sources within the scene in a stochastic (random) sort of way. They reflect or transmit from/through objects just like rays, except that there's a finite number of photons—each makes its way through the scene unlike rays which recursively spawn new rays at each intersection point. Based on random conditions, photons eventually stick to surfaces, like shown at left. One of the goals of this type of photon mapping is to be able to render caustics, or focused concentration of photons, more or less. When rendering, what's important is the number of photons per unit area (why not volume?), that is, their density is what we're after. (Note: for those of you observant enough, you'll see that the photon map I have here doesn't match the other images—you're correct; this photon map, with only one light source, is what I used for debugging. It was clearer using one light that the caustic was not showing up opposite to where the light source was—turns out I was calculating distance incorrectly, d'oh!)

Sum up the photons' "flux" per ray intersection point, divide by their squared radius, and presto! We have caustics. Photon mapping also demonstrates a key aspect of careful program design: at each intersection point one has to find a number of the closest photons. The image at right shows 20 photons sampled at each intersection point from 2,000 initially shot out (fairly small numbers all told). With these numbers the image is rendered in about a minute. Increasing those numbers by an order of magnitude to 100 samples from 10,000 photons initially shot yields about a 9-minute render time. Meanwhile, increasing yet again to 500,000 photons and 500 samples takes...I don't yet know, still waiting...on the order of hours I expect. Ding! Just done "baking": 188.6 minutes, yup 3.14 (pi?) hours. The key aspect of program design is this search for closest photons—the program uses a kd-tree to find the k-closest photons in O(log n) time. It has to do this for every intersection point, of which there is a very large number. If no kd-tree was used, then the search would take O(n) every time, and I suspect it would have taken a lot longer to complete, perhaps days. So was all that extra number-crunching time worth it? Below are two images (10,000 photons on the left 500,000 photons on the right) that match the photon map above. See the difference? One could argue that the caustic boundaries and the caustic itself are a bit crisper in the image at right, but are they worth three hours?

Happy New Year!

2010 is history. Its last month was unseasonably cold. I'm not sure if that's official meteorologically speaking, but at least it seems that way to me. A cold December, with snow at Christmas. We've gotten spoiled by the hot summers and both long for the return of warmer temperatures. I remember when in years past Corey would be out mowing the lawn in December. Not this year; it's mostly a stay inside kind of winter. And at least two more months to go. Hopefully March will bring back nicer weather as it usually does.

And when inside, why not fire up the fire place, and take out a good book, and boil up some tea. That teapot is something Santa left last year. Our old "brown bettie" had chipped (mainly due to my clumsiness), so I wanted a replacement. I found this little cast iron pot and am quite pleased with it. Although a touch small, aesthetically I think it's very handsome, and being made of iron should be indestructible. As for reading, it's 2011, and it's the year of the electronic book. Just before Christmas the University was kind enough to equip me with an iPad, which I mainly intend to use for teaching purposes. Corey found a good app for this, PenUltimate, and I tested it with our home projector. I think with a decent stylus, I should be able to use this app for scribing lecture notes. The app produces electronic PDF notebooks of notes, which I put online for the benefit of my students. Another app, PDF Expert, has fairly nice SFTP transmission utilities which allows me to transfer PDFs from the iPad to my web server. So with both of these tools in hand, I think I'll be set for class when they start up again in just a couple of weeks. In the meantime, why not use the iPad's touted "killer app" for reading electronic books. Some say they can't seem to swtich to this style of reading, and prefer the traditional feel of paper in their hands. I thought I'd be like that too, but the iPad's iBook app (free) is growing on me rather quickly. It holds a small library of (free) books, the font is nice, its sepia coloring looks like a book, you can bookmark pages and highlight text. The highlighted text looks irregular and imprecise just like the real thing, except that the way in which you select text is precise to the letter. Very nice. This precise selection of words is also handy when looking up words in the dictionary—this feature I have to say is really well done. On the iPad you get a nice little window that pops up with the word's definition. I've already looked up a bunch of words having read several of Arthur Conan Doyle's Sherlock Holmes adventures, Rudyard Kipling's Rikki-Tikki-Tavi, and Philip K. Dick's The Eyes Have It—all pretty much short stories. Right now I'm reading Honoré de Balzac's The Marriage Contract. My brother suggested both Balzac and Descartes so I wanted to follow up on his recommendation—I've got Descartes' Discourse on the Method... bookmarked. It's a little profuse in its prose, but not bad for scientific observations made in the 17th century. The gist of it is: assume nothing, divide and conquer, verify each step. I suppose a fairly basic approach today, divide and conquer in particular is certainly a well known approach to algorithmic design. Still, I suppose someone had to write this down, and it's held up for over 400 years. Btw, the other nice feature of electronic books is that the bookmarks transfer over to your various ereaders: iBook is available on the iPhone as well, and when I transfer reading between the two devices, each "knows" where I left of previously. Quite convenient. No more dogearing paper books. The only nuisance with this is that you have to be on the grid...the net is becoming as much of a dependency as electricity...

Milford Sound

Our last stop on our New Zealand road trip was Milford Sound. There really isn't much there at Milford Sound apart from the lodge and campground (RV hookups for us) and the quay from which boat tours depart daily. On advice from the campervan people from whom we rented the vehicle I booked a powered site at the lodge (which we later found out was sold out). We also picked the smallest boat tour of Milford. The small boat was the best choice I think—not overcrowded and able to get close to the fjords (to see the waterfalls for example).

The fjords here are truly spectacular, although the weather can be somewhat unpredictable, meaning often cloudy and/or rainy, as it was when we visited. When sunny it must be really fantastic. The way the cliffs line up visually is also interesting: apparently when surveying the coastline, Cook (I think it was Cook) had missed the entry to Milford, not seeing it from the ship. One major annoyance here were the black (sand) flies. They were all over the place. They didn't bite, but were a real nuisance. The Maori legend had it that the flies were there so that tourists wouldn't stay too long and spoil the scenery.

The waterfalls pictured above was one of three (if I remember correctly) to which the boat came close to. So close in fact that at one of them I got pretty soaked when standing on the bow (just for fun). The boat also got close to some of the wildlife in the area. There were supposed to be penguins, and I think I saw three in the distance, but I wasn't sure if they were penguins or seagulls. We did get close to some seals lounging on the rocks. They found a fairly windy perch, which we were told they did to keep the flies off.

Horsing Around Te Anau

A couple more pics from Te Anau (this was me trying to shoot behind me with my left hand). When we were in Queenstown we saw an ad for horseback riding, but since we went on the jetboat, we didn't have time to go on a "horse trek" as they call it. So when we checked in to our campsite in Te Anau, Corey noticed a horseback riding pamphlet and so I called them. We were going to go for a late afternoon ride, but when we called they said they'd pick us up in 15 minutes! So we quickly changed, and walked out to wait for the pickup. I wasn't sure what to expect, since most other "rent-a-horses" I've been on have basically been lazy...they were hard to control and would only pick up some enthusiasm on the return leg. The place we went to, Westray Farm provided me with the best horseback riding experience I've ever had. Not only was the horse nice, responsive to my gentle steering with the reigns, but the trek itself was excellent—it wasn't just a out-and-back half-hour walk, this was a long, circular trek up a hill and around a couple of animal herds. We first walked through a herd of curious cows, and on the way back we split a group of sheep. The terrain was also the most challenging I've ever been on horseback—on the way down there were a few steep parts where I felt I really had to lean back in the saddle. The horses were rescued from a former life of racing. Perhaps that was why they were fairly nice: maybe they were grateful for their new life. Mind you, perhaps because they were race horses in their former life, a few of them were a little flighty. I may have been laughing in the pic below because Corey's horse was one of these (she got stuck with the type of horse that I usually get). She eventually switched with the farm owner's horse who then had to discipline the misbehaving horse (had to give it a whack on the neck to stop acting up :)

Road to Te Anau

After our brief stop in Bluff, we went in search of our next campsite. It was supposed to be some sort of Holiday Road campground close to the beach. The online description sounded good, but when we got there, boy was it ever a dump! And of course only one set of toilets was opened, making them unisex. Corey said no way was she going to be showering there and so off we went in search of the other campground in the proximity that offered a "farm experience". The farm experience was night and day difference—very well maintained place, nice toilets, and baby sheep! So Corey made the right call moving us to this place, as it was most pleasant. The lambs were quite friendly, especially when hungry.

Lamb feedings were at 8am and 6pm (sharp!) with the lambs bleeting rather loudly, reminding everyone when it was time. The lambs got milk bottles while the goat and adult sheep got solid food in pellet form. The farmer/campgroundskeeper gave us quite a bit of info about his farm, number of sheep, etc. One new factoid was that sheep are born with a long tail. But as they are rather poor self-cleaners, the tail gets bobbed, either at birth with some kind of hot iron, or like these lambs, they get a rubber band tightened on the tail, which, due to lack of circulation, eventually drops off. I dunno which method is less painful. On the one hand hot-knifing the tail would hurt, but it'd be over quickly. On the other hand the rubber band has to be worn for a while, and I'm sure it can't be very pleasant. Another interesting observation was that sheep have horizontally-slit eyes (unlike cats who have vertically-slit pupils, weird huh?).

After our most pleasant stay on the farm, we got on the road to Te Anau, which would be something of a staging point for our trip to Milford Sound. It's a good idea to do this as the road to Milford is fairly tricky (think old road to Whistler, especially that old 13 or 17 mile stretch that used to be fairly crappy to drive), and there are no gas stations at Milford. On the way to Te Anau we stopped at this outlook to take a look at the Tasman Sea. It was a pretty blustery day. Later in Te Anau the fellow whose horses we rode told us that out here fishermen can only go out 56 days of the year due to these high winds. Btw, as you can deduce, most of the pictures were taken by Corey.  She got mad at me the other day for using her photos that she took with my camera.  I don't know what the big deal was, but truth be told she does take really good photos, and I've neglected to give credit where it's due.  Sorry about that, hopefully I've now corrected this omission.

Bluff

Another shot of the camper. This was at a nice "rest area" or kind of lookout on the scenic route to Invercargill. The lookout was out on a meandering river (at right in the image, beyond the trees, so just slightly obscured). It was a pleasant enough place to have lunch.  The road was not very busy and so the place was pretty quiet.  Except for the occasional lamb bleeting.  As (bad) luck would have it, however, we weren't alone at this picnic site for long...just a few minutes later another campervan full of what sounded like French rolled up.  Of course they came out with their Gauloises, or whatever brand they were smoking...stinking up the place (I used to be one of these stinkers—I'm glad I'm not anymore, especially since we used to smoke inside vehicles, I bet the campervan would have stunk if we had kept that up).

Speaking of the campervan (I got up this Thanksgiving morning, fairly lazily, and my mind drifted back to waking up in the campervan, I guess I kind of miss it a bit :) here is what the interior looked like. I have to admit that its creature comforts were quite good.  Behind the driver's seat was the dining table which doubled as a bed although we never set that one up.  Instead, we ended up sleeping above the cab.  You can't quite see it in the pic, but there was a mattress up there and a ladder that would let us crawl up there.  It was a bit squishy, but manageable.  The back of the van had another bed (in all there were three, as this was a 6-berth van) that we mainly used as a sofa.  We slept there the first night but the fridge noise was a bit too loud.  The fridge is under the stove, to the left of the sink.  The tall white door you see is the toilet/shower.  All of this equipment is very similar to a large sailboat, and most of the onboard systems are the same, e.g., electrical, including panel on which you had to turn the water pump on/off, water, with usable and waste water holding tanks, gas, and diesel.  I can't now remember whether the sailboat we were on was the same but I think so—I'm pretty sure it too had a diesel engine and propane for cooking.  The procedure on both, if I remember correctly, was to keep the water pump off unless you were actually using the water as it tends to drain the house battery and pressurizes the water lines.  Everything else could be on, and had to be on, to provide load when the truck was plugged in (to "shore power" as we'd called it on the boat).  The van also had an inverter somewhere which provided alternating current for regular household appliances (like hairdryers or what have you; for me it was iPhone charger, which served as the morning alarm clock).

Later on that day we reached Invercargill, although we actually circumnavigated it, as it were.  Here we are arriving at the "end of the world", well, at least the paved or road-accessible world.  We are at the top of a pedestrian-accessible lookout just south of Invercargill, at a town called Bluff.  From here we could see the town as well as Stewart Island, which I think is the southernmost piece of land before Antarctica.  Behind us was some kind of industrial harbour where we could see large tankers getting loaded.  There may have been an aluminum smelter or something back there, I don't quite recall what the nature of the industry was.  At the end of the road was this signpost on which you can find distances to other destinations, e.g., London (18,958 km), New York (15,008 km), Sydney (2,000 km), etc.

Tautuku Bay

This picture deserves special mention. On the way to Invercargill from Dunedin we stopped at a lookout point: Florence Hill Lookout, with views of Long Point and Tautuku Beach (Bay).  To me this looked like my "Zihuatanejo", a beach that a character in the movie Shawshank Redemption escaped to.  It was meant as kind of a place for retirement.  And at the end of the peninsula you can see little shacks that look idyllic for finally getting away from it all...it's so remote that, according to the wikipedia entry, the huts are only accessible by all-terrain tractor.  It may be that the weather here is likely to be pretty harsh most of the year, but on that day it looked rather inviting.

Road to Dunedin

Our first destination was on the east coast: Dunedin (pronounced Doo-nee'-dyn), I think the largest of the cities we would visit. The drive from Queenstown took a couple of hours (was it three?) and it took me a while to get used to driving the big rig. Originally we had booked a two-person van, sort of like a small VW bus. They didn't have them so we went up to the next size, a 4-berth van like the one seen here but a bit smaller. When we got there they said we'd been "upgraded" to this 6-berth behemoth. It was roomy on the inside allright, but was a bit of a pig to drive.

Most of the roads were like the one shown here: pasture after pasture after pasture. And of course most dotted with sheep. In some cases cows or even deer (for venison). And all on the left side naturally. The campervan's steering wheel was on the right with the gearshift (automatic) to my left. I think our first choice was to be a stick shift, but I'm actually glad we ended up with an automatic. I've driven left-handed stick before (in Australia), and although I got used to it fairly quickly, the car I had then was much smaller.

Driving the behemoth was particularly perilous on one of the narrowest roads I've ever driven, Highcliff Road, or something like that, on the way to the royal albatross rookery. I don't think we actually have a shot or video of this road, however. I think my passenger was a bit too freaked out to be shooting camera. I think the GPS was to blame for this road selection because it was a bit of a shortcut over top of the cliff instead of skirting around the shore, like we chose to do on the way back. We didn't stay long at the rookery because in effect it was closed to visitors. This is the only place on earth where the albatross nest on land, or populated land at least. I think they also nest on some uninhabited island somewhere, but this is the only place that you can get to and see them in their natural habitat. So we were greatly disappointed to find out that we had happened to have been there in the three week period when they're nesting young and humans are not allowed to set foot there.

In Dunedin I was also hoping to do some shopping (always on the lookout for a nice jacket), but we got there too late and all the shops were closed by the time we managed to get in to town (this was the evening previous to our rookery excursion). We got to the "holiday" campsite (I think they're all called holiday-something-or-other). It was fairly nice, with fairly good facilities but I suppose it took us a little bit longer than usual to get settled in as it was our first one. And it so happened that the powered site we were to take was already occupied when we got there. So a bit of a mixup. We had powered sites at all four of our campsites. This was a smart move booking everything in advance as I think at least two of the sites were close to being fully booked (the last one surely was). All but one had good pump-out facilities, like the one you see here, where I learned how to dump out both of the campervan's holding tanks (grey and black water both).

Queenstown, NZ

The Rydges is where we stayed the first few nights in Queenstown before taking a few days to drive around the southern part of New Zealand's south island. This is also the hotel where the Asian Conference on Computer Vision was held, where I presented a paper at one of its workshops (on gaze sensing). Although eye tracking depends on computer vision techniques, this workshop was on a slightly different topic, more on eye detection and estimation of the direction of gaze rather than on eye tracking per se. Think of surveillance video, now try to estimate what people in the video are looking at, that's what the workshop's main theme was on. The paper I presented was on an automatic means of distinguishing eye movement patterns made when watching video. The tie-in to computer vision is that we compared eye movements made by humans with those predicted by a computer vision algorithm.

And then we went boating! I think this may have been the same jet boat ride that I once saw in a Warren Miller ski movie many years ago. In the winter Queenstown is a ski village, not unlike Aspen, Telluride, or Kelowna, for a few examples. I think Warren Miller may have filmed some skiing here and so it's likely that he may have also filmed the Shotover jet ride that we went on. It's only a 20 minute or so ride but it's pretty unique. Because the boat has two jet engines (instead of propellers), it can skim over very shallow parts of the river bed. The drivers are also well experienced and they get damn close to the rocky cliffs of the canyon we were in. They also spin the boat 360 degrees like you see here.

Toward the evening we went on a slightly slower craft, the TSS Earnslaw that you see behind me. This boat was constructed in the same year as the Titanic. This one had clearly survived and still sails today between Queenstown and Walter Peak Station, a sheep ranch (station == ranch in Kiwi). At the station, we enjoyed a traditional roast beef and Yorkshire pudding dinner. We missed the sit-down (first class) service and so made due with the buffet. I actually skipped the roast beef and went for the lamb shanks. After dinner we saw sheep dog herding and sheep shearing demonstrations. On the way back I took a look down to the Earnslaw's engine room. The vessel is driven by two coal-powered steam engines and functions as it would have done 100 years ago. There were two guys shoveling coal and an engineer who would control engine speed in response to the captain's commands relayed by the old-fashioned rotary dials (e.g., ahead full, full stop, etc.). After a couple of days in Queenstown we would embark on our road trip around the south island...

Flight to NZ

The flight to NZ is quite long: 5 hrs (ATL-LAX) + 12 hrs (LAX-AKL) + 2 hrs (AKL-ZQN) = 19 hrs, and that's just in the air, not counting layovers and time spent going through security. New Zealand's security is fairly strict about food and soil being brought in (I saw a little beagle sniff out some kind of pepperoni in one bag and a small bag of carrots in another—the dog could also sniff out food that was there but recently removed). They gave us a bit of a scolding for not declaring our hiking boots in our bags (which we really consider as running shoes). At left is a shot from the rear window of the plane as we approach NZ. The plane landed at about 07:50 so this is dawn as seen from the plane. The image doesn't do it justice, the eye could pick out the colors of the spectrum fairly easily.

At right is a shot from the plane from Auckland to Queenstown.  The south island has some pretty steep looking mountains, reminiscent of the Rockies, but with less foliage.  Queenstown, as it turns out, is an adventurer's destination.  Beside a couple of ski hills around here (too late for that unfortunately, we're here mid-spring), there is also a large glacier lake here.  So there are various sporting activities one could do here. Queenstown reminds me of a small alpine town, similar to Aspen maybe, or more like Kelowna rather, because it also has a kind of "ye olde British" feel to it, sort of like Victoria. Maybe it's like a blend of all three. I would love to try skiing New Zealand, but the length and cost of the flight really make that rather unlikely.

Below is a pic as we were being driven into tow—the cab driver took us on a scenic route and stopped at a nice vantage point. Below, to the right (at far right), is roughly where our hotel is at.  Across from the little bit of water is a tree-covered peninsula.  That is something like a tiny Stanley Park, that juts out from the town that is at the bottom of the peninsula, and at bottom right, unfortunately just out of the picture.  In town are numerous restaurants, pubs, and various kinds of shops.  Our goal today is go walk around there and look at various things (me, a leather jacket of course :)

Oct.22 Gig at Wingin' It

Our last two gigs were to near-empty audiences. I think at the last gig at Friar's Tavern at one point literally the only person in the audience was our soundman. It was strange but we treated it like practice. We'll be back there Dec.3 and hopefully it'll be more like Wingin' It depicted above at our last gig, Oct.22. I much prefer playing to a full room and at this gig we had a good turnout. In the pic someone wanted to blurt out something over the mic, so I got a couple minutes' break in which I could snap a quick pic on my iPhone. So you get to see what the room looks like from the drummer's point of view. This was probably one of our better gigs: we played well and I think the audience was getting into it, especially during the third set when we tend to play faster, more recognizable stuff. The Allman Brothers' One Way Out has a rather recognizable riff (and ride cymbal) that the audience usually responds to pretty well. I think we played that song particularly well and I had a blast banging out those snare rolls at the end of every verse.

Dylan

This past weekend we went to the Dylan concert held on campus in what is normally the basketball arena. An excellent show for which we had pretty decent seats except maybe a bit too close to the stage. It was great seeing Dylan and his band up there, but the sound was, for us, imbalanced as it was mainly directed toward the left ear. The highlight, for me I think, was Ballad of a Thin Man which they played at a pretty fast tempo. Come to think of it, they played most things at a pretty fast pace, which I rather enjoyed. I'm always being told by my band mates to slow down, but I think a slightly faster pace is better enjoyed by the audience.

Hounds at Friar's Tavern

This is a shot from The Hoodoo Hounds' gig on Oct.1. It's a new(ly refurbished) place called Friar's Tavern (the old Explorers'). The stage is pretty small there, but we managed to fit somehow. My drums were right behind our front man who said that I was trying to beat the snare through his head :) I like my snare to snap when I hit it, what can I say? For this gig our front man brought in some fancy equipment that can analyze the room acoustics and automatically balance the output while canceling feedback. It does this by having you stick a microphone in the middle of the room while it sends out white noise through the speakers. Some home theater systems do this as well. I think we sounded pretty good that night, but unfortunately we played to a non-existent audience. It ended up being a practice gig for us with the only person applauding being our sound man...Another gig is coming up this Friday (Oct.22) and hopefully there'll be a larger crowd.

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.