When you look at the code of a 35 year old game...

[ara]

... and you recognize, with a big grin on your face, an algorithm from a course you once had at university.

From F/A-18 Interceptor:

    _x = 0;
    d = _y * -2 + 3;
    if (0 < _y) {
      do {
        *xcoords = -_x;
        xcoords[1] = _x;
        *ycoords = -_y;
        ycoords[1] = _y;
        if (d < 0) {
          d = d + _x * 4 + 6;
        }
        else {
          d += (_x - _y) * 4 + 10;
          _y += -1;
          xcoords = xcoords + 2;
        }
        ycoords = ycoords + -2;
        _x += 1;
      } while (_x < _y);
     }
    if (_x == _y) {
      *xcoords = -_x;
      xcoords[1] = _x;
    }

Ten fake internet points for the nerd who recognizes it, too.

[rare_j]

I'm simultaneously relieved and annoyed not to be nerdy enough.

[Karlos]

It reminds me of Bresenham's line drawing algorithm...

[Thomas Richter]

That is not a line drawer. This is a circle drawer (or parts of it). There are similar algorithms to draw any conic section. That is, rotated ellipses, parabola and hyperbola. It all goes down to the fact that a conic section is the zero set of a quadratic function, and an edge-tracer of a quadratic function only requires linear operations (thus, no multiplications and no divisions).

To give you some reference, DPaint uses a similar algorithm for drawing slanted ellipses (not the above Bresenham, but the above conic section), unfortunately not as a very good implementation.

[Megalomaniac]

Sounds like your tutor from back then was ahead of his time. Does it look like particularly good code to you?

[Bruce Abbott]

Originally Posted by ara

When you look at the code... From F/A-18 Interceptor:

You decompiled the machine code?

[ara]

Originally Posted by Bruce Abbott

You decompiled the machine code?

Trying my best Quite a challenge, but it's progressing (very slowly). Do you know whether anybody has published the source code or is willing to share it?

And yes, it's the Bresenham's circle drawing algorithm. Straight from the textbook: https://www.geeksforgeeks.org/bresen...ing-algorithm/

The game uses it to draw the sun and the head of the pilot.

[A500]

Hold on, was F/A18 Interceptor coded in C? Or did the author use also assembly code to make the 3D so fast?

[Karlos]

Do I get any nert points for mentioning the word Bresenham at least? C'mon, I really need nerd validation just now

[Bruce Abbott]

Originally Posted by Karlos

Do I get any nert points for mentioning the word Bresenham at least? C'mon, I really need nerd validation just now

No. One glance should have told you this wasn't Bresenham's line algorithm.

I first learned about Bresenham back in 1980 when I was creating a 6800 based computer from scratch. I wanted to draw lines in the 'hires' 256x192 screen of the MC6847 video display generator, and the simplicity of this algorithm blew me away! I had almost no computing knowledge and very few resources, not even a assembler - just the machine code monitor that I wrote from scratch and a copy of the 6800 Software Gourmet Guide and Cookbook by Robert Findley.

[Karlos]

No, it's Bresenham's circle algorithm. It's the name I'm panhandling for validation over.

[Bruce Abbott]

Originally Posted by Karlos

No, it's Bresenham's circle algorithm. It's the name I'm panhandling for validation over.

No, that's not how it works. To be a nerd you have to be "a person who is extremely enthusiastic and knowledgeable about a particular subject, especially one of specialist or niche interest". Just dropping names doesn't count. Trying to get nerd points for something you are clearly wrong about does the opposite. It may seem a little harsh, but that's just the way it works in nerd land.

Note that if you keep going on about it you risk being called a 'lamer'. To avoid this I suggest posting some other obscure technical detail that only a true nerd would know. Alternatively you could claim an acceptable excuse such as that you typed circle but the autocorrect changed it to line, or the cat jumped on the keyboard. That happens to me all the time, and I don't even have a cat!

[gimbal]

That's how much this decade sucks. You can't even call yourself a nerd without getting denied.

[Karlos]

Alternatively you could claim an acceptable excuse such as that you typed circle but the autocorrect changed it to line, or the cat jumped on the keyboard.

I mean that totally did happen, except it was thumbs and my android phone's increasingly ludicrous idea of what it thinks I want to say...

[Karlos]

Originally Posted by gimbal

That's how much this decade sucks. You can't even call yourself a nerd without getting denied.

I dunno, this decade you only have to identify as a nerd, and anyone contradicting you is a vicious bigot that must be cancelled.

[ara]

Originally Posted by A500

Hold on, was F/A18 Interceptor coded in C? Or did the author use also assembly code to make the 3D so fast?

Most of it was written in assembly code as far as I can tell. Only the high-level stuff (initialization of the screen, music, etc.) was written in C.

The piece that I showed was written in assembly, too. It's just the decompilation that shows it in C.

[A500]

Originally Posted by ara

Most of it was written in assembly code as far as I can tell. Only the high-level stuff (initialization of the screen, music, etc.) was written in C.

The piece that I showed was written in assembly, too. It's just the decompilation that shows it in C.

Ah, okay. Thank you for the clarification! I wasn't actually aware that original assembly code can be decompiled into a higher-level language.

[Bruce Abbott]

Originally Posted by A500

Ah, okay. Thank you for the clarification! I wasn't actually aware that original assembly code can be decompiled into a higher-level language.

Depends on what the original source code was. If it was written directly in assembler (not extracted from C compiler output) then technically you would be translating it to C, not decompiling it.

[Minuous]

So did you decompile it by hand or is there finally a decent decompiler available for the Amiga?

[hooverphonique]

Is it even possible to reliably identify that some binary was compiled from C? I mean, you can generally tell by the structure of the disassembly if it originally was compiled from a higher level language, or written directly in asm, but how would you identify it as originating from C?