From 51f8430027ceaf7590d826221230cbe2fc1af2ec Mon Sep 17 00:00:00 2001 From: Sadeep Madurange Date: Wed, 24 Dec 2025 19:21:25 +0800 Subject: Change to log/journal style. --- _site/log/matrix-digital-rain/index.html | 162 +++++++------------------------ 1 file changed, 33 insertions(+), 129 deletions(-) (limited to '_site/log/matrix-digital-rain/index.html') diff --git a/_site/log/matrix-digital-rain/index.html b/_site/log/matrix-digital-rain/index.html index 659922d..f47ac5e 100644 --- a/_site/log/matrix-digital-rain/index.html +++ b/_site/log/matrix-digital-rain/index.html @@ -2,12 +2,12 @@ - Recreating the Matrix rain with ANSI escape sequences + Matrix Rain: 2025 refactor - Recreating the Matrix rain with ANSI escape sequences + Matrix Rain: 2025 refactor @@ -41,141 +41,45 @@
-

RECREATING THE MATRIX RAIN WITH ANSI ESCAPE SEQUENCES

+

MATRIX RAIN: 2025 REFACTOR

21 DECEMBER 2025

-

My 2022 implementation of the Matrix rain had too many loose ends. Unicode -support was inflexible: the character set had to be a single contiguous block -with no way to mix ASCII with something like Katakana; Phosphor decay level was -stored in a dedicated array–still don’t understand why I did that when I had -already used bit-packing for the RGB channels; The algorithm was difficult to -decipher. The 2022 version worked, but that’s not the same thing as correct.

- -

I began by placing the decay factor in the LSB of the 4-byte RGB value. The PD -value plays a somewhat analogous role to an alpha channel in that both -influence transparency. However, they work very differently. So, I avoided -labelling it A so as not to cause confusion:

- -
enum {
-    R,  /* Red   */
-    G,  /* Green */
-    B,  /* Blue  */ 
-    PD  /* Phosphor decay level */
-};
-
-typedef union color_tag {
-    uint32_t value;
-    unsigned char color[4];
-} color;
-
- -

The decision to use union over more portable bit twiddling was made three years -ago, as I recall, for readability. Seeing as all my systems are little-endian, -this is unlikely to cause any trouble. Besides, if union is never to be used, -why is it in the language anyway?

- -

The blend() function, which emulates the dim afterglow of Phosphor by eroding -the RGB channels towards the background, with minor refactoring, remains as -elegant as it did three years ago:

- -
#define DECAY_MPLIER  2
-
-static inline void blend(matrix *mat,
-    size_t row, size_t col)
-{
-    unsigned char *color;
-
-    color = mat->rgb[index(mat, row, col)].color;
-    color[R] = color[R] - (color[R] - RGB_BG_RED) / DECAY_MPLIER;
-    color[G] = color[G] - (color[G] - RGB_BG_GRN) / DECAY_MPLIER;
-    color[B] = color[B] - (color[B] - RGB_BG_BLU) / DECAY_MPLIER;
-}
-
- -

While the memory inefficiency of Phosphor decay was a technical oversight I -hadn’t noticed, the limitation around mixing nonadjacent Unicode blocks was a -nagging concern even three years ago. So, a fix was long overdue.

- -

In the new version, I introduced an array that enables a user to add as -many Unicode blocks as they want. The insert_code() function picks a block -from it at random, and then picks a character from that block at random:

- -
#define UNICODE(min, max)  (((uint64_t)max << 32) | min)
-
-static uint64_t glyphs[] = {
-    UNICODE(0x0021, 0x007E), /* ASCII */
-    UNICODE(0xFF65, 0xFF9F), /* Half-width Katakana */
-};
-
-static uint8_t glyphlen = (sizeof glyphs) / (sizeof glyphs[0]);
-
-static inline void insert_code(matrix *mat,
-    size_t row, size_t col) 
-{
-    uint64_t block;
-    uint32_t unicode_min, unicode_max;
-
-    block = glyphs[(rand() % glyphlen)];
-    unicode_min = (uint32_t)block;
-    unicode_max = (uint32_t)(block >> 32);
-
-    mat->code[index(mat, row, col)] = rand()
-        % (unicode_max - unicode_min)
-        + unicode_min;
-}
-
- -

The Unicode blocks are stored in 8-byte containers: the low four bytes form the -first codepoint and the high four bytes the last. Here, I chose bitwise -operations over unions because, first and foremost, the operations themselves -are trivial and idiomatic, and the UNICODE() macro simplifies the management of -charsets.

- -

The init_term() function is the arbiter of this zero-dependency software. It -prepares the graphical environment so that I can interact with it via ANSI -escape codes instead of unnecessary layers of abstraction:

- -
static inline int init_term(const struct winsize *ws) 
-{
-    struct termios ta;
-
-    if (tcgetattr(STDIN_FILENO, &ta) == 0) {
-        ta.c_lflag &= ~ECHO;
-        if (tcsetattr(STDIN_FILENO, TCSANOW, &ta) == 0) {
-            wprintf(L"\x1b[48;2;%d;%d;%dm", 
-                RGB_BG_RED, RGB_BG_GRN, RGB_BG_BLU);
-            wprintf(L"%s", ANSI_FONT_BOLD);
-            wprintf(L"%s", ANSI_CRSR_HIDE);
-            wprintf(L"%s", ANSI_CRSR_RESET);
-            wprintf(L"%s", ANSI_SCRN_CLEAR);
-            setvbuf(stdout, 0, _IOFBF, 0);
-            ioctl(STDOUT_FILENO, TIOCGWINSZ, ws);
-            return 1;
-        }
-    }
-    return 0;
-}
-
- -

insert_code() seeds the Matrix, blend() creates the old monochrome CRT display -nostalgia, and ANSI control sequences paint the screen. The result is a digital -rain that captures the original Matrix aesthetic with high visual fidelity:

- -
$ cc -O3 main.c -o matrix
-$ ./matrix
-
+

Fixed the Unicode issue finally. Can now mix ASCII + Katakana.

+ +

Took me 2 hours to decipher how this even works. For future me: mat.col[] +stores shuffled column indices, mat.row[] tracks last updated row per column. +shuffle() randomizes the working set, index i (line 333) and lines 364-370 draw +one column at a time, swap() rotates columns in and out. That’s the rain.

+ +

Moved Phosphor decay level into the LSB of the RGB union - should’ve done this +in 2022 instead of separate array. WTF was I thinking?

+ +

Keeping the RGB/PD union as it is. I know the ‘portability’ nerds hate it, but +I’m on a little-endian machine, and I’m the only one reading this. It’s +cleaner.

+ +

New charset array works. UNICODE(min, max) macro packs the range into uint64. +insert_code() picks random block, unpacks it, and picks random char. Elegant.

+ +

Looks a lot like the original now:

-

There was no cause to measure the program’s performance characteristics -precisely; it’s gentle on the CPU. On my ThinkPad T490 running OpenBSD, which -has a resolution of 1920x1080, it uses about 2-3% of the CPU, with occasional -jumps of up to about 8%; the cores remain silent, the fans don’t whir, the rain -falls in quiet.

+

Using half-width Katakana (U+FF61-U+FF9F) because full-width characters break +columns.

+ +

blend() is still good, left it alone.

+ +

Tossed the license and automake cruft. Just cc -O3 main.c -o matrix. Don’t +need the ceremony.

+ +

Performance regressions: none. Runs like a charm on the T490. 2% CPU. No +whirring fans.

-

Files: source.tar.gz

+

Commit: +03f8d87

by W. D. Sadeep Madurange

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