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Anton's Research Ramblings

Mesa3D

I'm absolutely ruined from the weekend/last week's training and having a very early Sunday night, so jotting some notes while I'm having a rare quiet moment. I got a refurbished Lenovo laptop for doing slides and a bit of away-from-desk work because my previous laptop met with an unfortunate accident. It doesn't have a graphics chip, of course, but I thought I'd take a look at the mesa3d project. This is an open-source implementation of OpenGL, which provides up to OpenGL 3.1 support, and also does software emulation.

I took my OpenGL 4 "Hello Triangle" demo, and built that with some locally compiled GLFW and GLEW libraries. If I leave out the hint to GLFW to which version it should use, it reports "OpenGL 2.1". If I explicitly say "use 3.1" it crashes - I guess the software emulation doesn't extend that far. Using the default 2.1, it does open an OpenGL window, and clears the screen with no errors, but it doesn't show my triangle. The shaders needed a few minor changes to back-port to the GLSL version used by OpenGL 2.1.

And it works. These are pretty much the same shaders as are used in the current generation of WebGL, and OpenGL ES 1 and 2. Haven't looked at 3 yet. Interestingly, the per-pixel shading works on a computer with no graphics adaptor (I think), which I guess is mesa doing a fine job of emulating things. I wasn't able to do anything with shaders on previous PCs, even though they had early Nvidia adapters. I just checked, and I can also run http://antongerdelan.net/dolphin_rescue/ on this laptop, which is all shader-based. Interesting. I probably would have gotten away with making my full-on OpenGL game in OpenGL 2.1 - none of the advanced shader techniques are at all reliable anyway, but it's probably a lot of hassle for little return at this stage. I have no idea if Windows would then require a mesa build - I guess so, as the built-in stuff is still MS' horrible OpenGL 1.1 implementation, if I recall correctly.

So Mesa is really very good these days. I haven't speed tested it, but I wouldn't doubt that I could run my game on it. It looks like it's still GNU/Linux focused, but does a good job of running OpenGL 2.1 with shaders.

Some Things to Try This Week

I've been taking advantage of a quiet period at work to reformat my tutorials for Kindle, and revising tutorials as I go. It's a long, long slow process. I am also building a collection of stand-alone demos - one for each tutorial. I've nearly nearly finished them. I want to add some extra material for the e-book that I don't have in the tutorial series - related topics and opinion pieces/suggestions. I have a few neat tricks that didn't really fit quite well into the tutorial series, but are still useful as appendix stuff I think; code structure, handling meshes/buffers/arrays, some optimisations, etc. Things to try this week:

I got into Android NDK programming last year, and I never really finished off the little 3d demo that I made. The Android development kit is the most over-complicated horrible programming that I've ever done. Java is just a disgusting waste of time, so I used the NDK ("native" development kit) instead, which gives you a way to write more efficient code for things like OpenGL ES, which I wanted to do. The whole kit of tools and things for Android is absolutely horrific, and I really don't enjoy using it at all. Apple has a much more pleasant kit. The main problem is that you can't just load a file, or use printf...or compile locally on the machine...or ssh to the machine... or do anything really outside of the custom framework. It took me a week of hair-pulling to redirect printf to the custom Android log manager, and hook up the asset manager so that I could parse plain ASCII files from C. All the files in your app .apk get compressed, so you either have to hand-write a decompressor with libz, or use the built-in Asset Manager, which is Java only. To do this you use a C-Java binding called "JNI", which stands for "an abomination that crawled out of the Pit". Once you finally get all this set up you are okay and can code into OpenGL ES. I couldn't get C++ working nicely so I just ported my maths library to C'89, which was kind of cleaner than the C++ version. The disappointing thing is that you still need to use a mixed bag of semi-broken custom Android tools - and at least occasionally use Eclipse and Java (burrrgh).

I ordered a whole bunch of Arduino stuff a couple of months ago. Hopefully that will actually arrive this week, and I can get into some micro-controller programming.