Grit 0.8.1

by |
5

Grit 0.8.1 is out now. I've made three somewhat small changes here. First, there was some trouble with shared palettes/tiles if there was no -O or -S option. “Trouble”, as in segmentation fault. This should now be fixed.

I've also reformatted the include guards from __FOO__ to GRIT_FOO_H. GCC uses that format for internal #defines and it is very territorial about such matters. So, say, when you have elf.png, GCC gets cranky because that would hide its own __ELF__, and guess who wins out there? Again, thanks for pointing these things out, Quirky.

The last item is the addition of column-major tiling. This can be useful for horizontal scrolling games, since the data or the columns are all adjacent instead of a whole scanline apart. A second benefit of this mode is that rendering to tiles is made considerably easier (and a little bit faster too).

In case you hadn't noticed yet, I've also put the manual on-line. This shows the basic options for grit and wingrit, and now there's a description of how to use it in makefiles as well. This includes how the building the grit-demo project works. This one's quite interesting, so please check it out.


Project link.

Artsy fartsy

by |
2

I've been working on a few functions for rendering onto tiles recently. Yesterday was the turn of a rectangle filler. The traditional routine of double-looping over a pixel-plotter would be slow in every case, but for tiled surfaces it's positively evil, so I made something that divides the rectangle in 5 areas and fills them using by words or better. Yes, this is a little tricky but I figured the speed increase of up to 300 would be worth it.

For testing purposes, I filled each region with a different color so that ifwhen something went wrong, I could easily identify the problem. When playing around with the test app, I more or less accidentally came up with this:

accidental mondriaan

Hmmm ... Mondriaany.

Anyway, it seems that this thing went alright. So now tonclib also has plot, hline, vline, line, rect and frame functions for 4bpp tiled modes. No, there's no blitting yet. In anyone wants that, I'm going to insist on some mental hazard pay.

grit 0.8

by |
1

It's time for another Grit release. There are three important changes compared to previous versions.

First, palette merging is in (and there was much rejoicing). If you use the -pS option, a shared palette will be created and used in the graphics. Note that I still think palette merging should be performed on the images themselves and not in the output phase. If anyone's interested, I do have a small app that can do just this.

Another big change is that handling of shared data is now done correctly. The previous version required two runs for this: one for the non-shared stuff, and then another for the tileset itself. You also had to take care to disable the shared item for the individual runs, otherwise the (useless) intermediates would be exported as well. Grit 0.8 fixes all this. You can provide multiple images and request a shared tileset and/or palette (with -pS, -gS, or -fx) and it should work right. Grit will export the individual parts first and save exporting the shared data for the end. For example, if you have 5 files to be converted to maps with a shared tileset, you'll get 5 maps, and one tileset and palette (instead of 5 of each like 0.7 did). You can tune the shared output names with -S and -O (uppercase s and o) if necessary.

Thirdly, there is a new binary file-type available. I'm calling it GRF, for Grit RIFF File. This places the graphics, maps and palette in RIFF chunks. The idea behind this was to have related data in a single file instead of three different binaries. The chunked data-format also allows easier extension and it's easy to make a generic loader for it too. For details (including such a loader), see the the manual. The -ftr option creates a GRF file, and you can also create GRF-formatted C/asm arrays using -fr.

I've also added something I like to call ‘fake’ compression, -Z0 (Z zero). This adds a header word to the data similar to the ones that the compressed data have. This consistency of data-formats is essential for the generic data-loader.


As I mentioned before, there is also a proper demo project to show how you can use grit and its various options. Take note of how it uses a separate makefile to prepare the graphics. This way you can keep the main makefile pretty clean and it makes it easier to insert customized conversion rules. Note: to build the demo project, make sure GRIT points to the updated binary.


Linkies

And this year^Hdecade's award for irony goes to ...

by |
Reply

Expelled : No intelligence allowed! Give them a hearty round of scorn and ridicule, folks.


OK, perhaps a bit of backstory is in order here.

There's this strange thing going on in the USA known as the Creation-evolution controversy. In a nutshell, on one side you have the Theory of Evolution, accepted by all but a fraction of the scientists and supported by evidence from multiple fields; and on the other you have groups (usually motivated by their religion or ignorance and frequently both) screaming “nuh-uh!”, backed up by arguments ranging from utterly insane, to fabrications, misunderstandings, red herrings, and “I dunno, Magic Man dun it”. No, I'm not embellishing here: there are long lists of creationists claims that often make no sense at all, but are still used even after being debunked decades ago. As an example how silly these can be, consider the Banana argument. And no, this is not a parody; they're absolutely serious.

After the scientists got so fed up by the constant misrepresentations that they won't even debate anymore and several defeats in courts, the creationists came up with a new strategy: Intelligent Design (ID). They've been quite clever with this, actually. For one, they're leaving the Bible out of it and claiming that life's complexity can only come about through an intelligent, yet unnamed (wink, wink), designer. They also claim that all they want is a fair hearing; that the scientists are being mean with their insistence on evidence and refusal to accept bogus reasoning.


Enter Expelled. You'd have to read the wikipedia page for details, but the idea behind the movie is to highlight this repression by scientists; that the evolutionists are actively ‘expelling’ people critical of evolution. It so happens that they've interviewed a number of evolutionary biologists (under false pretenses) for their views on the subject. This is now widely regarded as a bad move.

You see, one of them happened to be PZ Myers, a vocal critic of creationism and other irrationality on his blog pharyngula. You can see how hostile he is in this video (I'd point to the Expelled trailers with the interview, but they pulled it). Ever since the interview, he and other science-bloggers have been keeping an eye on the movie, pointing out flaws in the producers' arguments whenever they went public with anything.

And now it gets interesting. About two weeks ago, there was a screening of the movie in Minneapolis. He reserved a place via their website, went to the theatre … but was barred from entering. To spell it out: here's a movie accusing evolutionists of expelling their critics, expelling their critics. And then lying about it afterwards! Repeatedly! Seriously, you just can't make this stuff up.

Naturally, this is now all over the blogosphere. The original account has well over 1600 comments. Many other science bloggers have commented on it as well. Greg Laden's blog has a list of over 100 links, including to stories from the NY Times and Salon. Another interesting detail is that Myers was accompanied by Richard Dawkins (yes, that Richard Dawkins), who did get in. The two had a nice little discussion afterwards, which can be seen here.


Other interesting links


Testing latex

by |
Reply

No, not the rubber stuff; the math stuff. According to the WP codex, it should be as simple as this:

$latex i\hbar\frac{\partial}{\partial t}\left|\Psi(t)\right>=H\left|\Psi(t)\right>$

OK, so that doesn't work :\. Ah right, that's just for when you have the blog under the wordpress.org itself. Right … mimetex then.

* finds wp-latexrender.zip here.

* looks for install procedure.

* looks for clear install procedure.

* tries the install anyway.

* reads the mimetex.php in full because while everyone says to update the path directories, it's unclear what to set them to especially as they seem to be double.

* sighs and rewrites the whole function because the variables and how they are used are … silly.


Right. How about this then: "[tex]x^2+y^2[/tex]"?

x^2+y^2

Yaaay! :D. And now for some more interesting forms:

E = mc^2 \label{clever}

OK, so apparently I can't put the labels into mimetex. Let's see what else will and will not work ...

\lim_{n \to \infty}\sum_{k=1}^n \frac{1}{k^2} = \frac{\pi^2}{6}

Okay ... so the default version doesn't like newlines either. So let's tweak the formula so that all whitespace (and repeated white) it replaced by a single space ... '/\s+/ /g' should do the trick.

\LARGE\tilde y=\left\{ {\ddot x\text{ if $\vec x$ odd}\atop\hat{\,\bar x+1}\text{ if even}}\right.
\small\hspace{10}\unitlength{.75} \picture(120,220){~(60,200){\circle(120,40)}~(0,20){\line(0,180)} (5,189;0,-30){\pict(110,20){(c20,10;70;2){ \pict(40,20){(20,10){\circle(40,20)}(c10,10)+(c30,10)-}}~}~} (119,20){\line(0,180)}~(60,20){\circle(120,40;34)}}
\bold C( \theta, \phi) = \bold R_y(\phi) \cdot \bold R_x(\theta) = \begin{bmatrix} \cos (\phi) & \sin(\phi) \sin(\theta) & -\sin(\phi) \cos(\theta)\\ 0 & \cos(\theta) & \sin(\theta) \\ \sin(\phi) & -\cos(\phi)\sin(\theta) & \cos(\phi)\sin(\theta) \end{bmatrix}

And to try some inline stuff: m \vec{a} = -k \vec{x} . Or maybe m \vec{a} = -k \vec{x} for something a little smaller. Yay, that works as well.

Anyway, for anyone who also wants math on their site, you can get mimetex from from http://www.forkosh.com/mimetex.html. Although the site starts with the source, there are precompiled binaries in the back somewhere. I would recommend rewriting mimetex.php, though: I found it somewhat tricky to get it working. It relies on 4 paths, but it doesn't exactly say what they were supposed to represent or what they should be set to; when I tried it locally the only way to get them to work was to do stuff that had little relation to the fill-in-the-blanks parts of the paths.

It doesn't like whitespace either in or around the formula, so removing that can be useful; so is feeding the through rawurlencode() if you want to put it into the url: HTMLTidy really doesn't like all the backslashes and stuff in the url. Adding options to the [tex] tag is also a good idea (like size; see above). And what's especially useful is a preview mode that doesn't render to a file. That way you won't be left with hundreds of little temporary bitmaps for all the failed variants. (I suppose I could give you mine, but it's not finished yet.)

Lastly, if you're new to TeX, consider using this site as an editor. There is a larger manual on the mimetex maintainer's site, but this little tool is very useful.

computing, costs and caching, oh my

by |
Reply

Via coding horror, I stumbled upon a simply wonderful talk by Herb Sutter about various performance issues like how much operations cost. It also discusses how memory, latency and machine architecture can affect that cost how this has changed over the years. You can find the slides and a video of the presentation at http://nwcpp.org/Meetings/2007/09.html.

Be prepared for a total geek-out. This is highly technical (and awesome, but that's bordering on a tautology) stuff and probably not for the faint of heart. Slides 6 and 7, for example, around the 23m mark) show the value of cache compared to getting something from RAM, and just how bad retrieval from disk is. Later (slides 13 and on; around 55m in the video), when it comes to threads and how a compiler or even hardware may screw you over not do what you want to do, or even what you tell it to do, people how still have them are allowed to run to their moms for safety. By Patina, that is just nasty.

Near the end Sutter discusses the differences between using vectors, lists and sets and what the penalties for the latter are for something as simple add adding all the values in them. This starts at around slide 22, or 1h40m. Even if the rest is gobblyjook, this part is easy to understand. Basically, low footprint and sequential accesses are Good Things, even if you have cache and stuff. Especially when you have cache and stuff.

Tonc:setup update

by |
Reply

Finally got round to updating Tonc's dev setup page. It finally mentions devkitPro's template makefiles and the basics of how to use them. I've also added a list of potential problems you may encounter when installing/upgrading devkitARM or just building projects. I have not updated the downloadables yet because there's still a few unfinished edits there. I just wanted to get this one out of the way because it's so very, very overdue.

Little Rocket Man

by |
1

For those familiar with Half-Life 2 Ep 2, you may have noticed the achievement list. Many of these are easy to do even on a first run, but there are three in particular that take some effort: “Neighborhood Watch”, “Little Rocket Man” and “Get Some Grub”. The requirement for the second really is somewhat mind-boggling: yes, it really means getting the garden gnome you find in the first building aaaaalll the way to the rocket in the White Forest base at the end. This seems insane – it is insane. But I finally managed it:



For others attempting this: the only really taxing part is across the train-tracks with that damn chopper on your tail. My strategy was to carry the gnome to safe-points first by hiding under the wagons, then going back for the car. In the second leg, the chopper will at the base once you get close enough; you can use this to secure safe passage. Also, once inside the garage do not leave the gnome on the table: the table will disappear when you get back from the auto-gun, apparently taking the gnome with it. Once you reach the rocket, close the hatch yourself! This is also part of the requirement. The rest is mostly getting out of the car because there's no gnome-sized seatbelts, although I hear there's a way to get it stuck in the rear window somehow.

With that done, I only need the Grub achievement for the whole set. I missed eight of them. Eight! Out of 333! :(

memcpy and memset replacements for GBA/NDS

by |
3

The standard C functions for copying and filling are memcpy() and memset(). They're part of the standard library, are easy to use and are often implemented with some optimizations so that they're usually faster than manual looping. The DKA version, for example will fill as words if the alignments and sizes allow for it. This can be much faster than doing the loops yourself.

There is, however, one small annoying fact about these two: they're not VRAM-safe. If the alignment and size aren't right for the word transfers, they will transfer bytes. Not only will this be slow, of course, but because you can't write to VRAM in bytes, the data will be corrupted.

The solutions for this have mostly come down to “so don't do that then”. Often, this can be sufficient: tiles in VRAM are word-aligned by definition, and source graphics data can and should be word-aligned anyway. However, now that I'm finally working on a bitmap blitter for 8bpp and 16bpp, I find that it's simply not enough. So I wrote the following set of functions to serve as replacements.

The code

My main goal here was to create smallish and portable replacements, not to have the greatest and fastestest code around because that's rather platform dependent. Yes, even the difference between GBA and NDS should matter, because of the differences in ldr/str times and caching.

There are 5 functions here. The main functions here are tonccpy and __toncset for copying and filling words, respectively. The other 3 are interfaces for __toncset for filling 8-bit, 16-bit and 32-bit data; you need these for, say, filling with a color instead of 8-bit data. For the rest of the discussion, I will use the name “toncset” for the internal routine for convenience.

Continue reading →