Martin Geisler Online

There’s a storm here in Denmark tonight — I can hear how the wind howls, as it sweeps past Skejbygaard. It’s kind of cozy to sit indoor and listen to the wind outside — not that I hear it that much, with XMMS running constantly on my computer…

I turn all my CD’s into Ogg Vorbis files using Grip. The latest addition to my collection is The Lord of the Rings Soundtrack which I got for my birthday. We can’t buy the film on DVD yet, but at least we can buy the soundtrack. When listening to it, you can see the film in your head — it’s actually very nice. Enya has made two of the tracks, which only makes things better :-)

I had my exam in Mat10 yesterday, and I passed. My question was about the Gram-Schmidt process. I started with the main theorem and proved some other theorems as I went. It went fairly well when I got started, and it was all over in about 10-15 minutes.

Now I’m getting ready for the next, and final, exam: dIntProg. I’ve switched places with another from my class, so that my exam is this Friday (the 18th) and not the 24th as it was originally. This means that I’ll be done with my exams roughly a week before schedule — very nice indeed! :-) After the exam on Friday, I’ll go to Aalborg, where I’ll stay till by birthday the 21st. I’ll no longer be a teenager after the 21st… I guess that means that I’ve grown up :-)

I showed you a 3D cube the other day — a cube modeled in OpenGL. I’ve now refined the cube so that it looks much better, and I have combined 27 of them into a Rubik’s Cube. You can rotate the cube as a unit, and you can rotate the individual sides. It’s actually pretty cool :-)

The cube is fully illuminated by a single light in the scene, and the individual cubes have their normals defined for all vertexes, so that they can reflect the light faithfully. The colored sides doesn’t shine very much, whereas the black, rounded edges have more intense highlights. At first I was somewhat confused by all the parameters that control the lighting in OpenGL, but it turned out to be pretty easy to work with.

You can download the source right here: /downloads/rubik/. You should be able to compile the code if you have a C++ compiler (such as g++) and the OpenGL library together with GLUT which is available for both Linux (that’s what I’ve been using) and Windows.

The program is still in a kind of pre-alpha state :-) It is my first attempt at learning OpenGL and C++. So far, I really like both OpenGL and C++. I’ve been very positively surprised by C++ — it behaves just as you would expect, and it has all sorts of advanced and cool features like template functions and classes, full support for object-oriented programming and the Standard Library.

As you might have guessed, then I’m studying for my upcoming exam in linear algebra, also know as Mat10. The exam is the 15th so there’s still plenty of time. I’ve now worked by way through all the subjects we will be tested in, and have made a (Danish) document in LaTeX with all the theorems and proofs. I’ve now written something for every subject — there’s even a proof of the nasty Cayley-Hamilton Theorem! At first I thought it was very confusing, but then I found a proof on the net (sorry — I didn’t save the link) that took the time to explain things properly, and that helped.

The exam is without preparation, so I’ll probably have to rehearse some more… I’ve never tried this kind of exam so I don’t know what to expect. It sounds a bit scary, that I have to be able to talk about a random subject — just like that. My last exam in math was with 20 minutes of time for preparations — plenty of time to look things up in the books and so on… But on the other hand, we wont get a grade for this exam — we either pass or fail. That should make things much easier.

I’ve placed my notes for the forthcoming exam in Mat10 (linear algebra) on the web. You’ll find them here. (The notes are in Danish)