Improvements to the 2D core

After spending the last 9 days fixing, improving and rewriting most of the 3D core, I looked for some 3D stuff to test. While searching I found a few 2D demos that still didn't work properly. They run without crashing, but were rendering incorrect stuff. The reason is quite simple: desmume doesn't support rotated / scaled sprites yet (among other bugs).

So, yesterday I decided that I should give a try to the 2D core, as the rotation / scale stuff looked like an effect called "rotozoomer", that I already coded in the past. The stuff looked simple, but actually took 2 entire envenings to work correctly. The implemention is far from being finished, but all the sprites that have scaling/rotation and I don't support, get rendered like in the last released desmume, so at least, I don't broke anything.

Currently, I only support rotation when sprite is 256 colours / direct color (16bits) and the sprite is not flipped. I think that I'll get 16 colour sprites support done in no time, but I've not yet looked at it. Supporting flipped sprites will be harder, as I don't have any demos that already do that. I guess I'll have to change some of the available examples to enable flipping in them.

Enough chit chat, this is an example of how it's working now, a rotated and scaled sprite, with double size (this last one simply doubles the clipping rectangle, so if you've an square rotated 45 degrees, corners don't get cut):

More stuff has been done/tested, you'll see in the (probably far in the future) release.

Perfection looks good

It's not a secret that I've spent the last days trying to get the DS Graphic FIFO commands working (also known as display lists). For those that don't know what I'm talking about, it's actually quite simple. If you want to render 3D objects in the DS, you've at least two ways to do it: inmediate and the FIFO. With inmediate, every vertex/normal/texture/etc coordinate is sent separately. It's theorically the slowest way. With the FIFO, you just have a queue of commands (vertex/normal/texture/etc), and then the DS interprets it. Well, enough chit chat.

This morning, I've finally fixed one of the bugs in my current core. The bug was quite stupid: the DS has 6 ways to send a vertex position, with different accuracy, and different number of components. One of them, is a relative position to the last coordinate sent, so, for example, if the last vertex was {1,0,0} and you want to set a new vertex at {1,2,3}, you cand just sent a relative vertex with coordinates {0,2,3}. That's a good idea, as the relative coordinates are actually half the size of a full accuracy vertex.

The differences are quite obvious:

I'll let you guess which one is the fixed one :P

Have fun, I'm back to coding.

DS 3D core fixes and enhacements

Since yesterday, I've been focused on fixing all the 3D demos that the devkitpro provides. As of now, I can say I fixed almost 95% of the issues with them. The 3D core was very primitive, just to name a few bugs, all the blending (transparency) was broken, all the texture formats were badly handed (the alpha was always a tiny value, so it broke all the transparency), and MANY others.

One of the things that I really wanted to fix, were the nehe samples, as only one of them ran. After adding all the missing 3D commands I could find missing, all of them run perfectly. Some screenshots about fixed things and examples of new features:

Just one of the demos I've doesn't run at all, and two others show very minor glitches (one of them the one with the alien sitting above). When I've finally fixed the missing bugs in the display list render code, I'll focus in the cpu core again.

DS hardware crash course

Well, last friday I decided, after a quite stressing work day, to work a bit on the Desmume. As a source base, I used the last source found in Normmatt's blog. After a bit of testing of the binary provided, I found a few tiny details, the one that catched most my attention, is that it failed to pass a lot of the tests of the ARMWrestler by Mic (of Dualis fame). So, as I like writing cpu cores, and I didn't know anything about ARM cpus, I decided to try to fix some of the tests to learn some ARM assembly.

After about 9h of hardcore debugging, I fixed more than half of the errors that it reported. The next day, after talking with Normmatt and sending him the improved core, he sent me an updated source base, that included the 3D and sound cores written by yopyop (the original author of desmume). One of the main bugs with the 3D, is that the screen where the 3D is shown flickers a lot due to the way Desmume handles window updating. There were lots of other bugs, like the 3D api init failing on certain configurations, most of the libnds examples not working, etc.

So, lots of work ahead :)

Too keep a long story short, I'll just enumerate the changes:

- Fixed 3D core init.
- Fixed crash if a non mapped key was pressed.
- Preliminar flicker fix (this is VERY preliminar).
- Added lots of 3D display list command handling (needs more work).
- Fixed some of the 3D commands.
- Added sort of a "debug texture" when texture format is not yet handled.
- Fixes on 3D texturing.
- Thumb LDR and STR opcodes fixed.
- Arm LDR** and STR** opcodes fixed.
- Other fixes I cannot remember :P

And that in only 3 days :P

Here's an screenshot of a fix in the texturing (probably the easiest fix of all), of the nehe10 example provided with the libnds (most of the other nehe samples work, too):


Don't even ask about a release date, it'll be released when it's done. Neither about testing or something in that line.

First post

In this blog I'll talk mainly about emulator developing. Right now I'm focused on working on DSmume, and improving the 3D core and the cpu cores.